gcc/ada/g-pehage.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --        G N A T . P E R F E C T _ H A S H _ G E N E R A T O R S           --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 2002-2011, AdaCore                     --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with Ada.IO_Exceptions;       use Ada.IO_Exceptions;
  33 with Ada.Characters.Handling; use Ada.Characters.Handling;
  34 with Ada.Directories;
  35
  36 with GNAT.Heap_Sort_G;
  37 with GNAT.OS_Lib;      use GNAT.OS_Lib;
  38 with GNAT.Table;
  39
  40 package body GNAT.Perfect_Hash_Generators is
  41
  42    --  We are using the algorithm of J. Czech as described in Zbigniew J.
  43    --  Czech, George Havas, and Bohdan S. Majewski ``An Optimal Algorithm for
  44    --  Generating Minimal Perfect Hash Functions'', Information Processing
  45    --  Letters, 43(1992) pp.257-264, Oct.1992
  46
  47    --  This minimal perfect hash function generator is based on random graphs
  48    --  and produces a hash function of the form:
  49
  50    --             h (w) = (g (f1 (w)) + g (f2 (w))) mod m
  51
  52    --  where f1 and f2 are functions that map strings into integers, and g is
  53    --  a function that maps integers into [0, m-1]. h can be order preserving.
  54    --  For instance, let W = {w_0, ..., w_i, ..., w_m-1}, h can be defined
  55    --  such that h (w_i) = i.
  56
  57    --  This algorithm defines two possible constructions of f1 and f2. Method
  58    --  b) stores the hash function in less memory space at the expense of
  59    --  greater CPU time.
  60
  61    --  a) fk (w) = sum (for i in 1 .. length (w)) (Tk (i, w (i))) mod n
  62
  63    --     size (Tk) = max (for w in W) (length (w)) * size (used char set)
  64
  65    --  b) fk (w) = sum (for i in 1 .. length (w)) (Tk (i) * w (i)) mod n
  66
  67    --     size (Tk) = max (for w in W) (length (w)) but the table lookups are
  68    --     replaced by multiplications.
  69
  70    --  where Tk values are randomly generated. n is defined later on but the
  71    --  algorithm recommends to use a value a little bit greater than 2m. Note
  72    --  that for large values of m, the main memory space requirements comes
  73    --  from the memory space for storing function g (>= 2m entries).
  74
  75    --  Random graphs are frequently used to solve difficult problems that do
  76    --  not have polynomial solutions. This algorithm is based on a weighted
  77    --  undirected graph. It comprises two steps: mapping and assignment.
  78
  79    --  In the mapping step, a graph G = (V, E) is constructed, where = {0, 1,
  80    --  ..., n-1} and E = {(for w in W) (f1 (w), f2 (w))}. In order for the
  81    --  assignment step to be successful, G has to be acyclic. To have a high
  82    --  probability of generating an acyclic graph, n >= 2m. If it is not
  83    --  acyclic, Tk have to be regenerated.
  84
  85    --  In the assignment step, the algorithm builds function g. As G is
  86    --  acyclic, there is a vertex v1 with only one neighbor v2. Let w_i be
  87    --  the word such that v1 = f1 (w_i) and v2 = f2 (w_i). Let g (v1) = 0 by
  88    --  construction and g (v2) = (i - g (v1)) mod n (or h (i) - g (v1) mod n).
  89    --  If word w_j is such that v2 = f1 (w_j) and v3 = f2 (w_j), g (v3) = (j -
  90    --  g (v2)) mod (or to be general, (h (j) - g (v2)) mod n). If w_i has no
  91    --  neighbor, then another vertex is selected. The algorithm traverses G to
  92    --  assign values to all the vertices. It cannot assign a value to an
  93    --  already assigned vertex as G is acyclic.
  94
  95    subtype Word_Id   is Integer;
  96    subtype Key_Id    is Integer;
  97    subtype Vertex_Id is Integer;
  98    subtype Edge_Id   is Integer;
  99    subtype Table_Id  is Integer;
 100
 101    No_Vertex : constant Vertex_Id := -1;
 102    No_Edge   : constant Edge_Id   := -1;
 103    No_Table  : constant Table_Id  := -1;
 104
 105    type Word_Type is new String_Access;
 106    procedure Free_Word (W : in out Word_Type) renames Free;
 107    function New_Word (S : String) return Word_Type;
 108
 109    procedure Resize_Word (W : in out Word_Type; Len : Natural);
 110    --  Resize string W to have a length Len
 111
 112    type Key_Type is record
 113       Edge : Edge_Id;
 114    end record;
 115    --  A key corresponds to an edge in the algorithm graph
 116
 117    type Vertex_Type is record
 118       First : Edge_Id;
 119       Last  : Edge_Id;
 120    end record;
 121    --  A vertex can be involved in several edges. First and Last are the bounds
 122    --  of an array of edges stored in a global edge table.
 123
 124    type Edge_Type is record
 125       X   : Vertex_Id;
 126       Y   : Vertex_Id;
 127       Key : Key_Id;
 128    end record;
 129    --  An edge is a peer of vertices. In the algorithm, a key is associated to
 130    --  an edge.
 131
 132    package WT is new GNAT.Table (Word_Type, Word_Id, 0, 32, 32);
 133    package IT is new GNAT.Table (Integer, Integer, 0, 32, 32);
 134    --  The two main tables. WT is used to store the words in their initial
 135    --  version and in their reduced version (that is words reduced to their
 136    --  significant characters). As an instance of GNAT.Table, WT does not
 137    --  initialize string pointers to null. This initialization has to be done
 138    --  manually when the table is allocated. IT is used to store several
 139    --  tables of components containing only integers.
 140
 141    function Image (Int : Integer; W : Natural := 0) return String;
 142    function Image (Str : String;  W : Natural := 0) return String;
 143    --  Return a string which includes string Str or integer Int preceded by
 144    --  leading spaces if required by width W.
 145
 146    function Trim_Trailing_Nuls (Str : String) return String;
 147    --  Return Str with trailing NUL characters removed
 148
 149    Output : File_Descriptor renames GNAT.OS_Lib.Standout;
 150    --  Shortcuts
 151
 152    EOL : constant Character := ASCII.LF;
 153
 154    Max  : constant := 78;
 155    Last : Natural  := 0;
 156    Line : String (1 .. Max);
 157    --  Use this line to provide buffered IO
 158
 159    procedure Add (C : Character);
 160    procedure Add (S : String);
 161    --  Add a character or a string in Line and update Last
 162
 163    procedure Put
 164      (F  : File_Descriptor;
 165       S  : String;
 166       F1 : Natural;
 167       L1 : Natural;
 168       C1 : Natural;
 169       F2 : Natural;
 170       L2 : Natural;
 171       C2 : Natural);
 172    --  Write string S into file F as a element of an array of one or two
 173    --  dimensions. Fk (resp. Lk and Ck) indicates the first (resp last and
 174    --  current) index in the k-th dimension. If F1 = L1 the array is considered
 175    --  as a one dimension array. This dimension is described by F2 and L2. This
 176    --  routine takes care of all the parenthesis, spaces and commas needed to
 177    --  format correctly the array. Moreover, the array is well indented and is
 178    --  wrapped to fit in a 80 col line. When the line is full, the routine
 179    --  writes it into file F. When the array is completed, the routine adds
 180    --  semi-colon and writes the line into file F.
 181
 182    procedure New_Line (File : File_Descriptor);
 183    --  Simulate Ada.Text_IO.New_Line with GNAT.OS_Lib
 184
 185    procedure Put (File : File_Descriptor; Str : String);
 186    --  Simulate Ada.Text_IO.Put with GNAT.OS_Lib
 187
 188    procedure Put_Used_Char_Set (File : File_Descriptor; Title : String);
 189    --  Output a title and a used character set
 190
 191    procedure Put_Int_Vector
 192      (File   : File_Descriptor;
 193       Title  : String;
 194       Vector : Integer;
 195       Length : Natural);
 196    --  Output a title and a vector
 197
 198    procedure Put_Int_Matrix
 199      (File  : File_Descriptor;
 200       Title : String;
 201       Table : Table_Id;
 202       Len_1 : Natural;
 203       Len_2 : Natural);
 204    --  Output a title and a matrix. When the matrix has only one non-empty
 205    --  dimension (Len_2 = 0), output a vector.
 206
 207    procedure Put_Edges (File : File_Descriptor; Title : String);
 208    --  Output a title and an edge table
 209
 210    procedure Put_Initial_Keys (File : File_Descriptor; Title : String);
 211    --  Output a title and a key table
 212
 213    procedure Put_Reduced_Keys (File : File_Descriptor; Title : String);
 214    --  Output a title and a key table
 215
 216    procedure Put_Vertex_Table (File : File_Descriptor; Title : String);
 217    --  Output a title and a vertex table
 218
 219    function Ada_File_Base_Name (Pkg_Name : String) return String;
 220    --  Return the base file name (i.e. without .ads/.adb extension) for an
 221    --  Ada source file containing the named package, using the standard GNAT
 222    --  file-naming convention. For example, if Pkg_Name is "Parent.Child", we
 223    --  return "parent-child".
 224
 225    ----------------------------------
 226    -- Character Position Selection --
 227    ----------------------------------
 228
 229    --  We reduce the maximum key size by selecting representative positions
 230    --  in these keys. We build a matrix with one word per line. We fill the
 231    --  remaining space of a line with ASCII.NUL. The heuristic selects the
 232    --  position that induces the minimum number of collisions. If there are
 233    --  collisions, select another position on the reduced key set responsible
 234    --  of the collisions. Apply the heuristic until there is no more collision.
 235
 236    procedure Apply_Position_Selection;
 237    --  Apply Position selection and build the reduced key table
 238
 239    procedure Parse_Position_Selection (Argument : String);
 240    --  Parse Argument and compute the position set. Argument is list of
 241    --  substrings separated by commas. Each substring represents a position
 242    --  or a range of positions (like x-y).
 243
 244    procedure Select_Character_Set;
 245    --  Define an optimized used character set like Character'Pos in order not
 246    --  to allocate tables of 256 entries.
 247
 248    procedure Select_Char_Position;
 249    --  Find a min char position set in order to reduce the max key length. The
 250    --  heuristic selects the position that induces the minimum number of
 251    --  collisions. If there are collisions, select another position on the
 252    --  reduced key set responsible of the collisions. Apply the heuristic until
 253    --  there is no collision.
 254
 255    -----------------------------
 256    -- Random Graph Generation --
 257    -----------------------------
 258
 259    procedure Random (Seed : in out Natural);
 260    --  Simulate Ada.Discrete_Numerics.Random
 261
 262    procedure Generate_Mapping_Table
 263      (Tab  : Table_Id;
 264       L1   : Natural;
 265       L2   : Natural;
 266       Seed : in out Natural);
 267    --  Random generation of the tables below. T is already allocated
 268
 269    procedure Generate_Mapping_Tables
 270      (Opt  : Optimization;
 271       Seed : in out Natural);
 272    --  Generate the mapping tables T1 and T2. They are used to define fk (w) =
 273    --  sum (for i in 1 .. length (w)) (Tk (i, w (i))) mod n. Keys, NK and Chars
 274    --  are used to compute the matrix size.
 275
 276    ---------------------------
 277    -- Algorithm Computation --
 278    ---------------------------
 279
 280    procedure Compute_Edges_And_Vertices (Opt : Optimization);
 281    --  Compute the edge and vertex tables. These are empty when a self loop is
 282    --  detected (f1 (w) = f2 (w)). The edge table is sorted by X value and then
 283    --  Y value. Keys is the key table and NK the number of keys. Chars is the
 284    --  set of characters really used in Keys. NV is the number of vertices
 285    --  recommended by the algorithm. T1 and T2 are the mapping tables needed to
 286    --  compute f1 (w) and f2 (w).
 287
 288    function Acyclic return Boolean;
 289    --  Return True when the graph is acyclic. Vertices is the current vertex
 290    --  table and Edges the current edge table.
 291
 292    procedure Assign_Values_To_Vertices;
 293    --  Execute the assignment step of the algorithm. Keys is the current key
 294    --  table. Vertices and Edges represent the random graph. G is the result of
 295    --  the assignment step such that:
 296    --    h (w) = (g (f1 (w)) + g (f2 (w))) mod m
 297
 298    function Sum
 299      (Word  : Word_Type;
 300       Table : Table_Id;
 301       Opt   : Optimization) return Natural;
 302    --  For an optimization of CPU_Time return
 303    --    fk (w) = sum (for i in 1 .. length (w)) (Tk (i, w (i))) mod n
 304    --  For an optimization of Memory_Space return
 305    --    fk (w) = sum (for i in 1 .. length (w)) (Tk (i) * w (i)) mod n
 306    --  Here NV = n
 307
 308    -------------------------------
 309    -- Internal Table Management --
 310    -------------------------------
 311
 312    function Allocate (N : Natural; S : Natural := 1) return Table_Id;
 313    --  Allocate N * S ints from IT table
 314
 315    ----------
 316    -- Keys --
 317    ----------
 318
 319    Keys : Table_Id := No_Table;
 320    NK   : Natural  := 0;
 321    --  NK : Number of Keys
 322
 323    function Initial (K : Key_Id) return Word_Id;
 324    pragma Inline (Initial);
 325
 326    function Reduced (K : Key_Id) return Word_Id;
 327    pragma Inline (Reduced);
 328
 329    function  Get_Key (N : Key_Id) return Key_Type;
 330    procedure Set_Key (N : Key_Id; Item : Key_Type);
 331    --  Get or Set Nth element of Keys table
 332
 333    ------------------
 334    -- Char_Pos_Set --
 335    ------------------
 336
 337    Char_Pos_Set     : Table_Id := No_Table;
 338    Char_Pos_Set_Len : Natural;
 339    --  Character Selected Position Set
 340
 341    function  Get_Char_Pos (P : Natural) return Natural;
 342    procedure Set_Char_Pos (P : Natural; Item : Natural);
 343    --  Get or Set the string position of the Pth selected character
 344
 345    -------------------
 346    -- Used_Char_Set --
 347    -------------------
 348
 349    Used_Char_Set     : Table_Id := No_Table;
 350    Used_Char_Set_Len : Natural;
 351    --  Used Character Set : Define a new character mapping. When all the
 352    --  characters are not present in the keys, in order to reduce the size
 353    --  of some tables, we redefine the character mapping.
 354
 355    function  Get_Used_Char (C : Character) return Natural;
 356    procedure Set_Used_Char (C : Character; Item : Natural);
 357
 358    ------------
 359    -- Tables --
 360    ------------
 361
 362    T1     : Table_Id := No_Table;
 363    T2     : Table_Id := No_Table;
 364    T1_Len : Natural;
 365    T2_Len : Natural;
 366    --  T1  : Values table to compute F1
 367    --  T2  : Values table to compute F2
 368
 369    function  Get_Table (T : Integer; X, Y : Natural) return Natural;
 370    procedure Set_Table (T : Integer; X, Y : Natural; Item : Natural);
 371
 372    -----------
 373    -- Graph --
 374    -----------
 375
 376    G     : Table_Id := No_Table;
 377    G_Len : Natural;
 378    --  Values table to compute G
 379
 380    NT : Natural := Default_Tries;
 381    --  Number of tries running the algorithm before raising an error
 382
 383    function  Get_Graph (N : Natural) return Integer;
 384    procedure Set_Graph (N : Natural; Item : Integer);
 385    --  Get or Set Nth element of graph
 386
 387    -----------
 388    -- Edges --
 389    -----------
 390
 391    Edge_Size : constant := 3;
 392    Edges     : Table_Id := No_Table;
 393    Edges_Len : Natural;
 394    --  Edges  : Edge table of the random graph G
 395
 396    function  Get_Edges (F : Natural) return Edge_Type;
 397    procedure Set_Edges (F : Natural; Item : Edge_Type);
 398
 399    --------------
 400    -- Vertices --
 401    --------------
 402
 403    Vertex_Size : constant := 2;
 404
 405    Vertices : Table_Id := No_Table;
 406    --  Vertex table of the random graph G
 407
 408    NV : Natural;
 409    --  Number of Vertices
 410
 411    function  Get_Vertices (F : Natural) return Vertex_Type;
 412    procedure Set_Vertices (F : Natural; Item : Vertex_Type);
 413    --  Comments needed ???
 414
 415    K2V : Float;
 416    --  Ratio between Keys and Vertices (parameter of Czech's algorithm)
 417
 418    Opt : Optimization;
 419    --  Optimization mode (memory vs CPU)
 420
 421    Max_Key_Len : Natural := 0;
 422    Min_Key_Len : Natural := 0;
 423    --  Maximum and minimum of all the word length
 424
 425    S : Natural;
 426    --  Seed
 427
 428    function Type_Size (L : Natural) return Natural;
 429    --  Given the last L of an unsigned integer type T, return its size
 430
 431    -------------
 432    -- Acyclic --
 433    -------------
 434
 435    function Acyclic return Boolean is
 436       Marks : array (0 .. NV - 1) of Vertex_Id := (others => No_Vertex);
 437
 438       function Traverse (Edge : Edge_Id; Mark : Vertex_Id) return Boolean;
 439       --  Propagate Mark from X to Y. X is already marked. Mark Y and propagate
 440       --  it to the edges of Y except the one representing the same key. Return
 441       --  False when Y is marked with Mark.
 442
 443       --------------
 444       -- Traverse --
 445       --------------
 446
 447       function Traverse (Edge : Edge_Id; Mark : Vertex_Id) return Boolean is
 448          E : constant Edge_Type := Get_Edges (Edge);
 449          K : constant Key_Id    := E.Key;
 450          Y : constant Vertex_Id := E.Y;
 451          M : constant Vertex_Id := Marks (E.Y);
 452          V : Vertex_Type;
 453
 454       begin
 455          if M = Mark then
 456             return False;
 457
 458          elsif M = No_Vertex then
 459             Marks (Y) := Mark;
 460             V := Get_Vertices (Y);
 461
 462             for J in V.First .. V.Last loop
 463
 464                --  Do not propagate to the edge representing the same key
 465
 466                if Get_Edges (J).Key /= K
 467                  and then not Traverse (J, Mark)
 468                then
 469                   return False;
 470                end if;
 471             end loop;
 472          end if;
 473
 474          return True;
 475       end Traverse;
 476
 477       Edge  : Edge_Type;
 478
 479    --  Start of processing for Acyclic
 480
 481    begin
 482       --  Edges valid range is
 483
 484       for J in 1 .. Edges_Len - 1 loop
 485
 486          Edge := Get_Edges (J);
 487
 488          --  Mark X of E when it has not been already done
 489
 490          if Marks (Edge.X) = No_Vertex then
 491             Marks (Edge.X) := Edge.X;
 492          end if;
 493
 494          --  Traverse E when this has not already been done
 495
 496          if Marks (Edge.Y) = No_Vertex
 497            and then not Traverse (J, Edge.X)
 498          then
 499             return False;
 500          end if;
 501       end loop;
 502
 503       return True;
 504    end Acyclic;
 505
 506    ------------------------
 507    -- Ada_File_Base_Name --
 508    ------------------------
 509
 510    function Ada_File_Base_Name (Pkg_Name : String) return String is
 511    begin
 512       --  Convert to lower case, then replace '.' with '-'
 513
 514       return Result : String := To_Lower (Pkg_Name) do
 515          for J in Result'Range loop
 516             if Result (J) = '.' then
 517                Result (J) := '-';
 518             end if;
 519          end loop;
 520       end return;
 521    end Ada_File_Base_Name;
 522
 523    ---------
 524    -- Add --
 525    ---------
 526
 527    procedure Add (C : Character) is
 528       pragma Assert (C /= ASCII.NUL);
 529    begin
 530       Line (Last + 1) := C;
 531       Last := Last + 1;
 532    end Add;
 533
 534    ---------
 535    -- Add --
 536    ---------
 537
 538    procedure Add (S : String) is
 539       Len : constant Natural := S'Length;
 540    begin
 541       for J in S'Range loop
 542          pragma Assert (S (J) /= ASCII.NUL);
 543          null;
 544       end loop;
 545
 546       Line (Last + 1 .. Last + Len) := S;
 547       Last := Last + Len;
 548    end Add;
 549
 550    --------------
 551    -- Allocate --
 552    --------------
 553
 554    function Allocate (N : Natural; S : Natural := 1) return Table_Id is
 555       L : constant Integer := IT.Last;
 556    begin
 557       IT.Set_Last (L + N * S);
 558
 559       --  Initialize, so debugging printouts don't trip over uninitialized
 560       --  components.
 561
 562       for J in L + 1 .. IT.Last loop
 563          IT.Table (J) := -1;
 564       end loop;
 565
 566       return L + 1;
 567    end Allocate;
 568
 569    ------------------------------
 570    -- Apply_Position_Selection --
 571    ------------------------------
 572
 573    procedure Apply_Position_Selection is
 574    begin
 575       for J in 0 .. NK - 1 loop
 576          declare
 577             IW : constant String := WT.Table (Initial (J)).all;
 578             RW : String (1 .. IW'Length) := (others => ASCII.NUL);
 579             N  : Natural := IW'First - 1;
 580
 581          begin
 582             --  Select the characters of Word included in the position
 583             --  selection.
 584
 585             for C in 0 .. Char_Pos_Set_Len - 1 loop
 586                exit when IW (Get_Char_Pos (C)) = ASCII.NUL;
 587                N := N + 1;
 588                RW (N) := IW (Get_Char_Pos (C));
 589             end loop;
 590
 591             --  Build the new table with the reduced word. Be careful
 592             --  to deallocate the old version to avoid memory leaks.
 593
 594             Free_Word (WT.Table (Reduced (J)));
 595             WT.Table (Reduced (J)) := New_Word (RW);
 596             Set_Key (J, (Edge => No_Edge));
 597          end;
 598       end loop;
 599    end Apply_Position_Selection;
 600
 601    -------------------------------
 602    -- Assign_Values_To_Vertices --
 603    -------------------------------
 604
 605    procedure Assign_Values_To_Vertices is
 606       X : Vertex_Id;
 607
 608       procedure Assign (X : Vertex_Id);
 609       --  Execute assignment on X's neighbors except the vertex that we are
 610       --  coming from which is already assigned.
 611
 612       ------------
 613       -- Assign --
 614       ------------
 615
 616       procedure Assign (X : Vertex_Id) is
 617          E : Edge_Type;
 618          V : constant Vertex_Type := Get_Vertices (X);
 619
 620       begin
 621          for J in V.First .. V.Last loop
 622             E := Get_Edges (J);
 623
 624             if Get_Graph (E.Y) = -1 then
 625                Set_Graph (E.Y, (E.Key - Get_Graph (X)) mod NK);
 626                Assign (E.Y);
 627             end if;
 628          end loop;
 629       end Assign;
 630
 631    --  Start of processing for Assign_Values_To_Vertices
 632
 633    begin
 634       --  Value -1 denotes an uninitialized value as it is supposed to
 635       --  be in the range 0 .. NK.
 636
 637       if G = No_Table then
 638          G_Len := NV;
 639          G := Allocate (G_Len, 1);
 640       end if;
 641
 642       for J in 0 .. G_Len - 1 loop
 643          Set_Graph (J, -1);
 644       end loop;
 645
 646       for K in 0 .. NK - 1 loop
 647          X := Get_Edges (Get_Key (K).Edge).X;
 648
 649          if Get_Graph (X) = -1 then
 650             Set_Graph (X, 0);
 651             Assign (X);
 652          end if;
 653       end loop;
 654
 655       for J in 0 .. G_Len - 1 loop
 656          if Get_Graph (J) = -1 then
 657             Set_Graph (J, 0);
 658          end if;
 659       end loop;
 660
 661       if Verbose then
 662          Put_Int_Vector (Output, "Assign Values To Vertices", G, G_Len);
 663       end if;
 664    end Assign_Values_To_Vertices;
 665
 666    -------------
 667    -- Compute --
 668    -------------
 669
 670    procedure Compute (Position : String := Default_Position) is
 671       Success : Boolean := False;
 672
 673    begin
 674       if NK = 0 then
 675          raise Program_Error with "keywords set cannot be empty";
 676       end if;
 677
 678       if Verbose then
 679          Put_Initial_Keys (Output, "Initial Key Table");
 680       end if;
 681
 682       if Position'Length /= 0 then
 683          Parse_Position_Selection (Position);
 684       else
 685          Select_Char_Position;
 686       end if;
 687
 688       if Verbose then
 689          Put_Int_Vector
 690            (Output, "Char Position Set", Char_Pos_Set, Char_Pos_Set_Len);
 691       end if;
 692
 693       Apply_Position_Selection;
 694
 695       if Verbose then
 696          Put_Reduced_Keys (Output, "Reduced Keys Table");
 697       end if;
 698
 699       Select_Character_Set;
 700
 701       if Verbose then
 702          Put_Used_Char_Set (Output, "Character Position Table");
 703       end if;
 704
 705       --  Perform Czech's algorithm
 706
 707       for J in 1 .. NT loop
 708          Generate_Mapping_Tables (Opt, S);
 709          Compute_Edges_And_Vertices (Opt);
 710
 711          --  When graph is not empty (no self-loop from previous operation) and
 712          --  not acyclic.
 713
 714          if 0 < Edges_Len and then Acyclic then
 715             Success := True;
 716             exit;
 717          end if;
 718       end loop;
 719
 720       if not Success then
 721          raise Too_Many_Tries;
 722       end if;
 723
 724       Assign_Values_To_Vertices;
 725    end Compute;
 726
 727    --------------------------------
 728    -- Compute_Edges_And_Vertices --
 729    --------------------------------
 730
 731    procedure Compute_Edges_And_Vertices (Opt : Optimization) is
 732       X           : Natural;
 733       Y           : Natural;
 734       Key         : Key_Type;
 735       Edge        : Edge_Type;
 736       Vertex      : Vertex_Type;
 737       Not_Acyclic : Boolean := False;
 738
 739       procedure Move (From : Natural; To : Natural);
 740       function Lt (L, R : Natural) return Boolean;
 741       --  Subprograms needed for GNAT.Heap_Sort_G
 742
 743       --------
 744       -- Lt --
 745       --------
 746
 747       function Lt (L, R : Natural) return Boolean is
 748          EL : constant Edge_Type := Get_Edges (L);
 749          ER : constant Edge_Type := Get_Edges (R);
 750       begin
 751          return EL.X < ER.X or else (EL.X = ER.X and then EL.Y < ER.Y);
 752       end Lt;
 753
 754       ----------
 755       -- Move --
 756       ----------
 757
 758       procedure Move (From : Natural; To : Natural) is
 759       begin
 760          Set_Edges (To, Get_Edges (From));
 761       end Move;
 762
 763       package Sorting is new GNAT.Heap_Sort_G (Move, Lt);
 764
 765    --  Start of processing for Compute_Edges_And_Vertices
 766
 767    begin
 768       --  We store edges from 1 to 2 * NK and leave zero alone in order to use
 769       --  GNAT.Heap_Sort_G.
 770
 771       Edges_Len := 2 * NK + 1;
 772
 773       if Edges = No_Table then
 774          Edges := Allocate (Edges_Len, Edge_Size);
 775       end if;
 776
 777       if Vertices = No_Table then
 778          Vertices := Allocate (NV, Vertex_Size);
 779       end if;
 780
 781       for J in 0 .. NV - 1 loop
 782          Set_Vertices (J, (No_Vertex, No_Vertex - 1));
 783       end loop;
 784
 785       --  For each w, X = f1 (w) and Y = f2 (w)
 786
 787       for J in 0 .. NK - 1 loop
 788          Key := Get_Key (J);
 789          Key.Edge := No_Edge;
 790          Set_Key (J, Key);
 791
 792          X := Sum (WT.Table (Reduced (J)), T1, Opt);
 793          Y := Sum (WT.Table (Reduced (J)), T2, Opt);
 794
 795          --  Discard T1 and T2 as soon as we discover a self loop
 796
 797          if X = Y then
 798             Not_Acyclic := True;
 799             exit;
 800          end if;
 801
 802          --  We store (X, Y) and (Y, X) to ease assignment step
 803
 804          Set_Edges (2 * J + 1, (X, Y, J));
 805          Set_Edges (2 * J + 2, (Y, X, J));
 806       end loop;
 807
 808       --  Return an empty graph when self loop detected
 809
 810       if Not_Acyclic then
 811          Edges_Len := 0;
 812
 813       else
 814          if Verbose then
 815             Put_Edges      (Output, "Unsorted Edge Table");
 816             Put_Int_Matrix (Output, "Function Table 1", T1,
 817                             T1_Len, T2_Len);
 818             Put_Int_Matrix (Output, "Function Table 2", T2,
 819                             T1_Len, T2_Len);
 820          end if;
 821
 822          --  Enforce consistency between edges and keys. Construct Vertices and
 823          --  compute the list of neighbors of a vertex First .. Last as Edges
 824          --  is sorted by X and then Y. To compute the neighbor list, sort the
 825          --  edges.
 826
 827          Sorting.Sort (Edges_Len - 1);
 828
 829          if Verbose then
 830             Put_Edges      (Output, "Sorted Edge Table");
 831             Put_Int_Matrix (Output, "Function Table 1", T1,
 832                             T1_Len, T2_Len);
 833             Put_Int_Matrix (Output, "Function Table 2", T2,
 834                             T1_Len, T2_Len);
 835          end if;
 836
 837          --  Edges valid range is 1 .. 2 * NK
 838
 839          for E in 1 .. Edges_Len - 1 loop
 840             Edge := Get_Edges (E);
 841             Key  := Get_Key (Edge.Key);
 842
 843             if Key.Edge = No_Edge then
 844                Key.Edge := E;
 845                Set_Key (Edge.Key, Key);
 846             end if;
 847
 848             Vertex := Get_Vertices (Edge.X);
 849
 850             if Vertex.First = No_Edge then
 851                Vertex.First := E;
 852             end if;
 853
 854             Vertex.Last := E;
 855             Set_Vertices (Edge.X, Vertex);
 856          end loop;
 857
 858          if Verbose then
 859             Put_Reduced_Keys (Output, "Key Table");
 860             Put_Edges        (Output, "Edge Table");
 861             Put_Vertex_Table (Output, "Vertex Table");
 862          end if;
 863       end if;
 864    end Compute_Edges_And_Vertices;
 865
 866    ------------
 867    -- Define --
 868    ------------
 869
 870    procedure Define
 871      (Name      : Table_Name;
 872       Item_Size : out Natural;
 873       Length_1  : out Natural;
 874       Length_2  : out Natural)
 875    is
 876    begin
 877       case Name is
 878          when Character_Position =>
 879             Item_Size := 8;
 880             Length_1  := Char_Pos_Set_Len;
 881             Length_2  := 0;
 882
 883          when Used_Character_Set =>
 884             Item_Size := 8;
 885             Length_1  := 256;
 886             Length_2  := 0;
 887
 888          when Function_Table_1
 889            |  Function_Table_2 =>
 890             Item_Size := Type_Size (NV);
 891             Length_1  := T1_Len;
 892             Length_2  := T2_Len;
 893
 894          when Graph_Table =>
 895             Item_Size := Type_Size (NK);
 896             Length_1  := NV;
 897             Length_2  := 0;
 898       end case;
 899    end Define;
 900
 901    --------------
 902    -- Finalize --
 903    --------------
 904
 905    procedure Finalize is
 906    begin
 907       if Verbose then
 908          Put (Output, "Finalize");
 909          New_Line (Output);
 910       end if;
 911
 912       --  Deallocate all the WT components (both initial and reduced ones) to
 913       --  avoid memory leaks.
 914
 915       for W in 0 .. WT.Last loop
 916
 917          --  Note: WT.Table (NK) is a temporary variable, do not free it since
 918          --  this would cause a double free.
 919
 920          if W /= NK then
 921             Free_Word (WT.Table (W));
 922          end if;
 923       end loop;
 924
 925       WT.Release;
 926       IT.Release;
 927
 928       --  Reset all variables for next usage
 929
 930       Keys := No_Table;
 931
 932       Char_Pos_Set     := No_Table;
 933       Char_Pos_Set_Len := 0;
 934
 935       Used_Char_Set     := No_Table;
 936       Used_Char_Set_Len := 0;
 937
 938       T1 := No_Table;
 939       T2 := No_Table;
 940
 941       T1_Len := 0;
 942       T2_Len := 0;
 943
 944       G     := No_Table;
 945       G_Len := 0;
 946
 947       Edges     := No_Table;
 948       Edges_Len := 0;
 949
 950       Vertices := No_Table;
 951       NV       := 0;
 952
 953       NK := 0;
 954       Max_Key_Len := 0;
 955       Min_Key_Len := 0;
 956    end Finalize;
 957
 958    ----------------------------
 959    -- Generate_Mapping_Table --
 960    ----------------------------
 961
 962    procedure Generate_Mapping_Table
 963      (Tab  : Integer;
 964       L1   : Natural;
 965       L2   : Natural;
 966       Seed : in out Natural)
 967    is
 968    begin
 969       for J in 0 .. L1 - 1 loop
 970          for K in 0 .. L2 - 1 loop
 971             Random (Seed);
 972             Set_Table (Tab, J, K, Seed mod NV);
 973          end loop;
 974       end loop;
 975    end Generate_Mapping_Table;
 976
 977    -----------------------------
 978    -- Generate_Mapping_Tables --
 979    -----------------------------
 980
 981    procedure Generate_Mapping_Tables
 982      (Opt  : Optimization;
 983       Seed : in out Natural)
 984    is
 985    begin
 986       --  If T1 and T2 are already allocated no need to do it twice. Reuse them
 987       --  as their size has not changed.
 988
 989       if T1 = No_Table and then T2 = No_Table then
 990          declare
 991             Used_Char_Last : Natural := 0;
 992             Used_Char      : Natural;
 993
 994          begin
 995             if Opt = CPU_Time then
 996                for P in reverse Character'Range loop
 997                   Used_Char := Get_Used_Char (P);
 998                   if Used_Char /= 0 then
 999                      Used_Char_Last := Used_Char;
1000                      exit;
1001                   end if;
1002                end loop;
1003             end if;
1004
1005             T1_Len := Char_Pos_Set_Len;
1006             T2_Len := Used_Char_Last + 1;
1007             T1 := Allocate (T1_Len * T2_Len);
1008             T2 := Allocate (T1_Len * T2_Len);
1009          end;
1010       end if;
1011
1012       Generate_Mapping_Table (T1, T1_Len, T2_Len, Seed);
1013       Generate_Mapping_Table (T2, T1_Len, T2_Len, Seed);
1014
1015       if Verbose then
1016          Put_Used_Char_Set (Output, "Used Character Set");
1017          Put_Int_Matrix (Output, "Function Table 1", T1,
1018                         T1_Len, T2_Len);
1019          Put_Int_Matrix (Output, "Function Table 2", T2,
1020                         T1_Len, T2_Len);
1021       end if;
1022    end Generate_Mapping_Tables;
1023
1024    ------------------
1025    -- Get_Char_Pos --
1026    ------------------
1027
1028    function Get_Char_Pos (P : Natural) return Natural is
1029       N : constant Natural := Char_Pos_Set + P;
1030    begin
1031       return IT.Table (N);
1032    end Get_Char_Pos;
1033
1034    ---------------
1035    -- Get_Edges --
1036    ---------------
1037
1038    function Get_Edges (F : Natural) return Edge_Type is
1039       N : constant Natural := Edges + (F * Edge_Size);
1040       E : Edge_Type;
1041    begin
1042       E.X   := IT.Table (N);
1043       E.Y   := IT.Table (N + 1);
1044       E.Key := IT.Table (N + 2);
1045       return E;
1046    end Get_Edges;
1047
1048    ---------------
1049    -- Get_Graph --
1050    ---------------
1051
1052    function Get_Graph (N : Natural) return Integer is
1053    begin
1054       return IT.Table (G + N);
1055    end Get_Graph;
1056
1057    -------------
1058    -- Get_Key --
1059    -------------
1060
1061    function Get_Key (N : Key_Id) return Key_Type is
1062       K : Key_Type;
1063    begin
1064       K.Edge := IT.Table (Keys + N);
1065       return K;
1066    end Get_Key;
1067
1068    ---------------
1069    -- Get_Table --
1070    ---------------
1071
1072    function Get_Table (T : Integer; X, Y : Natural) return Natural is
1073       N : constant Natural := T + (Y * T1_Len) + X;
1074    begin
1075       return IT.Table (N);
1076    end Get_Table;
1077
1078    -------------------
1079    -- Get_Used_Char --
1080    -------------------
1081
1082    function Get_Used_Char (C : Character) return Natural is
1083       N : constant Natural := Used_Char_Set + Character'Pos (C);
1084    begin
1085       return IT.Table (N);
1086    end Get_Used_Char;
1087
1088    ------------------
1089    -- Get_Vertices --
1090    ------------------
1091
1092    function Get_Vertices (F : Natural) return Vertex_Type is
1093       N : constant Natural := Vertices + (F * Vertex_Size);
1094       V : Vertex_Type;
1095    begin
1096       V.First := IT.Table (N);
1097       V.Last  := IT.Table (N + 1);
1098       return V;
1099    end Get_Vertices;
1100
1101    -----------
1102    -- Image --
1103    -----------
1104
1105    function Image (Int : Integer; W : Natural := 0) return String is
1106       B : String (1 .. 32);
1107       L : Natural := 0;
1108
1109       procedure Img (V : Natural);
1110       --  Compute image of V into B, starting at B (L), incrementing L
1111
1112       ---------
1113       -- Img --
1114       ---------
1115
1116       procedure Img (V : Natural) is
1117       begin
1118          if V > 9 then
1119             Img (V / 10);
1120          end if;
1121
1122          L := L + 1;
1123          B (L) := Character'Val ((V mod 10) + Character'Pos ('0'));
1124       end Img;
1125
1126    --  Start of processing for Image
1127
1128    begin
1129       if Int < 0 then
1130          L := L + 1;
1131          B (L) := '-';
1132          Img (-Int);
1133       else
1134          Img (Int);
1135       end if;
1136
1137       return Image (B (1 .. L), W);
1138    end Image;
1139
1140    -----------
1141    -- Image --
1142    -----------
1143
1144    function Image (Str : String; W : Natural := 0) return String is
1145       Len : constant Natural := Str'Length;
1146       Max : Natural := Len;
1147
1148    begin
1149       if Max < W then
1150          Max := W;
1151       end if;
1152
1153       declare
1154          Buf : String (1 .. Max) := (1 .. Max => ' ');
1155
1156       begin
1157          for J in 0 .. Len - 1 loop
1158             Buf (Max - Len + 1 + J) := Str (Str'First + J);
1159          end loop;
1160
1161          return Buf;
1162       end;
1163    end Image;
1164
1165    -------------
1166    -- Initial --
1167    -------------
1168
1169    function Initial (K : Key_Id) return Word_Id is
1170    begin
1171       return K;
1172    end Initial;
1173
1174    ----------------
1175    -- Initialize --
1176    ----------------
1177
1178    procedure Initialize
1179      (Seed   : Natural;
1180       K_To_V : Float        := Default_K_To_V;
1181       Optim  : Optimization := Memory_Space;
1182       Tries  : Positive     := Default_Tries)
1183    is
1184    begin
1185       if Verbose then
1186          Put (Output, "Initialize");
1187          New_Line (Output);
1188       end if;
1189
1190       --  Deallocate the part of the table concerning the reduced words.
1191       --  Initial words are already present in the table. We may have reduced
1192       --  words already there because a previous computation failed. We are
1193       --  currently retrying and the reduced words have to be deallocated.
1194
1195       for W in Reduced (0) .. WT.Last loop
1196          Free_Word (WT.Table (W));
1197       end loop;
1198
1199       IT.Init;
1200
1201       --  Initialize of computation variables
1202
1203       Keys := No_Table;
1204
1205       Char_Pos_Set     := No_Table;
1206       Char_Pos_Set_Len := 0;
1207
1208       Used_Char_Set     := No_Table;
1209       Used_Char_Set_Len := 0;
1210
1211       T1 := No_Table;
1212       T2 := No_Table;
1213
1214       T1_Len := 0;
1215       T2_Len := 0;
1216
1217       G     := No_Table;
1218       G_Len := 0;
1219
1220       Edges     := No_Table;
1221       Edges_Len := 0;
1222
1223       Vertices := No_Table;
1224       NV       := 0;
1225
1226       S    := Seed;
1227       K2V  := K_To_V;
1228       Opt  := Optim;
1229       NT   := Tries;
1230
1231       if K2V <= 2.0 then
1232          raise Program_Error with "K to V ratio cannot be lower than 2.0";
1233       end if;
1234
1235       --  Do not accept a value of K2V too close to 2.0 such that once
1236       --  rounded up, NV = 2 * NK because the algorithm would not converge.
1237
1238       NV := Natural (Float (NK) * K2V);
1239       if NV <= 2 * NK then
1240          NV := 2 * NK + 1;
1241       end if;
1242
1243       Keys := Allocate (NK);
1244
1245       --  Resize initial words to have all of them at the same size
1246       --  (so the size of the largest one).
1247
1248       for K in 0 .. NK - 1 loop
1249          Resize_Word (WT.Table (Initial (K)), Max_Key_Len);
1250       end loop;
1251
1252       --  Allocated the table to store the reduced words. As WT is a
1253       --  GNAT.Table (using C memory management), pointers have to be
1254       --  explicitly initialized to null.
1255
1256       WT.Set_Last (Reduced (NK - 1));
1257
1258       --  Note: Reduced (0) = NK + 1
1259
1260       WT.Table (NK) := null;
1261
1262       for W in 0 .. NK - 1 loop
1263          WT.Table (Reduced (W)) := null;
1264       end loop;
1265    end Initialize;
1266
1267    ------------
1268    -- Insert --
1269    ------------
1270
1271    procedure Insert (Value : String) is
1272       Len  : constant Natural := Value'Length;
1273
1274    begin
1275       if Verbose then
1276          Put (Output, "Inserting """ & Value & """");
1277          New_Line (Output);
1278       end if;
1279
1280       for J in Value'Range loop
1281          pragma Assert (Value (J) /= ASCII.NUL);
1282          null;
1283       end loop;
1284
1285       WT.Set_Last (NK);
1286       WT.Table (NK) := New_Word (Value);
1287       NK := NK + 1;
1288
1289       if Max_Key_Len < Len then
1290          Max_Key_Len := Len;
1291       end if;
1292
1293       if Min_Key_Len = 0 or else Len < Min_Key_Len then
1294          Min_Key_Len := Len;
1295       end if;
1296    end Insert;
1297
1298    --------------
1299    -- New_Line --
1300    --------------
1301
1302    procedure New_Line (File : File_Descriptor) is
1303    begin
1304       if Write (File, EOL'Address, 1) /= 1 then
1305          raise Program_Error;
1306       end if;
1307    end New_Line;
1308
1309    --------------
1310    -- New_Word --
1311    --------------
1312
1313    function New_Word (S : String) return Word_Type is
1314    begin
1315       return new String'(S);
1316    end New_Word;
1317
1318    ------------------------------
1319    -- Parse_Position_Selection --
1320    ------------------------------
1321
1322    procedure Parse_Position_Selection (Argument : String) is
1323       N : Natural          := Argument'First;
1324       L : constant Natural := Argument'Last;
1325       M : constant Natural := Max_Key_Len;
1326
1327       T : array (1 .. M) of Boolean := (others => False);
1328
1329       function Parse_Index return Natural;
1330       --  Parse argument starting at index N to find an index
1331
1332       -----------------
1333       -- Parse_Index --
1334       -----------------
1335
1336       function Parse_Index return Natural is
1337          C : Character := Argument (N);
1338          V : Natural   := 0;
1339
1340       begin
1341          if C = '$' then
1342             N := N + 1;
1343             return M;
1344          end if;
1345
1346          if C not in '0' .. '9' then
1347             raise Program_Error with "cannot read position argument";
1348          end if;
1349
1350          while C in '0' .. '9' loop
1351             V := V * 10 + (Character'Pos (C) - Character'Pos ('0'));
1352             N := N + 1;
1353             exit when L < N;
1354             C := Argument (N);
1355          end loop;
1356
1357          return V;
1358       end Parse_Index;
1359
1360    --  Start of processing for Parse_Position_Selection
1361
1362    begin
1363       --  Empty specification means all the positions
1364
1365       if L < N then
1366          Char_Pos_Set_Len := M;
1367          Char_Pos_Set := Allocate (Char_Pos_Set_Len);
1368
1369          for C in 0 .. Char_Pos_Set_Len - 1 loop
1370             Set_Char_Pos (C, C + 1);
1371          end loop;
1372
1373       else
1374          loop
1375             declare
1376                First, Last : Natural;
1377
1378             begin
1379                First := Parse_Index;
1380                Last  := First;
1381
1382                --  Detect a range
1383
1384                if N <= L and then Argument (N) = '-' then
1385                   N := N + 1;
1386                   Last := Parse_Index;
1387                end if;
1388
1389                --  Include the positions in the selection
1390
1391                for J in First .. Last loop
1392                   T (J) := True;
1393                end loop;
1394             end;
1395
1396             exit when L < N;
1397
1398             if Argument (N) /= ',' then
1399                raise Program_Error with "cannot read position argument";
1400             end if;
1401
1402             N := N + 1;
1403          end loop;
1404
1405          --  Compute position selection length
1406
1407          N := 0;
1408          for J in T'Range loop
1409             if T (J) then
1410                N := N + 1;
1411             end if;
1412          end loop;
1413
1414          --  Fill position selection
1415
1416          Char_Pos_Set_Len := N;
1417          Char_Pos_Set := Allocate (Char_Pos_Set_Len);
1418
1419          N := 0;
1420          for J in T'Range loop
1421             if T (J) then
1422                Set_Char_Pos (N, J);
1423                N := N + 1;
1424             end if;
1425          end loop;
1426       end if;
1427    end Parse_Position_Selection;
1428
1429    -------------
1430    -- Produce --
1431    -------------
1432
1433    procedure Produce
1434      (Pkg_Name   : String  := Default_Pkg_Name;
1435       Use_Stdout : Boolean := False)
1436    is
1437       File : File_Descriptor := Standout;
1438
1439       Status : Boolean;
1440       --  For call to Close
1441
1442       function Array_Img (N, T, R1 : String; R2 : String := "") return String;
1443       --  Return string "N : constant array (R1[, R2]) of T;"
1444
1445       function Range_Img (F, L : Natural; T : String := "") return String;
1446       --  Return string "[T range ]F .. L"
1447
1448       function Type_Img (L : Natural) return String;
1449       --  Return the larger unsigned type T such that T'Last < L
1450
1451       ---------------
1452       -- Array_Img --
1453       ---------------
1454
1455       function Array_Img
1456         (N, T, R1 : String;
1457          R2       : String := "") return String
1458       is
1459       begin
1460          Last := 0;
1461          Add ("   ");
1462          Add (N);
1463          Add (" : constant array (");
1464          Add (R1);
1465
1466          if R2 /= "" then
1467             Add (", ");
1468             Add (R2);
1469          end if;
1470
1471          Add (") of ");
1472          Add (T);
1473          Add (" :=");
1474          return Line (1 .. Last);
1475       end Array_Img;
1476
1477       ---------------
1478       -- Range_Img --
1479       ---------------
1480
1481       function Range_Img (F, L : Natural; T : String := "") return String is
1482          FI  : constant String  := Image (F);
1483          FL  : constant Natural := FI'Length;
1484          LI  : constant String  := Image (L);
1485          LL  : constant Natural := LI'Length;
1486          TL  : constant Natural := T'Length;
1487          RI  : String (1 .. TL + 7 + FL + 4 + LL);
1488          Len : Natural := 0;
1489
1490       begin
1491          if TL /= 0 then
1492             RI (Len + 1 .. Len + TL) := T;
1493             Len := Len + TL;
1494             RI (Len + 1 .. Len + 7) := " range ";
1495             Len := Len + 7;
1496          end if;
1497
1498          RI (Len + 1 .. Len + FL) := FI;
1499          Len := Len + FL;
1500          RI (Len + 1 .. Len + 4) := " .. ";
1501          Len := Len + 4;
1502          RI (Len + 1 .. Len + LL) := LI;
1503          Len := Len + LL;
1504          return RI (1 .. Len);
1505       end Range_Img;
1506
1507       --------------
1508       -- Type_Img --
1509       --------------
1510
1511       function Type_Img (L : Natural) return String is
1512          S : constant String := Image (Type_Size (L));
1513          U : String  := "Unsigned_  ";
1514          N : Natural := 9;
1515
1516       begin
1517          for J in S'Range loop
1518             N := N + 1;
1519             U (N) := S (J);
1520          end loop;
1521
1522          return U (1 .. N);
1523       end Type_Img;
1524
1525       F : Natural;
1526       L : Natural;
1527       P : Natural;
1528
1529       FName : String := Ada_File_Base_Name (Pkg_Name) & ".ads";
1530       --  Initially, the name of the spec file, then modified to be the name of
1531       --  the body file. Not used if Use_Stdout is True.
1532
1533    --  Start of processing for Produce
1534
1535    begin
1536
1537       if Verbose and then not Use_Stdout then
1538          Put (Output,
1539               "Producing " & Ada.Directories.Current_Directory & "/" & FName);
1540          New_Line (Output);
1541       end if;
1542
1543       if not Use_Stdout then
1544          File := Create_File (FName, Binary);
1545
1546          if File = Invalid_FD then
1547             raise Program_Error with "cannot create: " & FName;
1548          end if;
1549       end if;
1550
1551       Put      (File, "package ");
1552       Put      (File, Pkg_Name);
1553       Put      (File, " is");
1554       New_Line (File);
1555       Put      (File, "   function Hash (S : String) return Natural;");
1556       New_Line (File);
1557       Put      (File, "end ");
1558       Put      (File, Pkg_Name);
1559       Put      (File, ";");
1560       New_Line (File);
1561
1562       if not Use_Stdout then
1563          Close (File, Status);
1564
1565          if not Status then
1566             raise Device_Error;
1567          end if;
1568       end if;
1569
1570       if not Use_Stdout then
1571
1572          --  Set to body file name
1573
1574          FName (FName'Last) := 'b';
1575
1576          File := Create_File (FName, Binary);
1577
1578          if File = Invalid_FD then
1579             raise Program_Error with "cannot create: " & FName;
1580          end if;
1581       end if;
1582
1583       Put      (File, "with Interfaces; use Interfaces;");
1584       New_Line (File);
1585       New_Line (File);
1586       Put      (File, "package body ");
1587       Put      (File, Pkg_Name);
1588       Put      (File, " is");
1589       New_Line (File);
1590       New_Line (File);
1591
1592       if Opt = CPU_Time then
1593          Put      (File, Array_Img ("C", Type_Img (256), "Character"));
1594          New_Line (File);
1595
1596          F := Character'Pos (Character'First);
1597          L := Character'Pos (Character'Last);
1598
1599          for J in Character'Range loop
1600             P := Get_Used_Char (J);
1601             Put (File, Image (P), 1, 0, 1, F, L, Character'Pos (J));
1602          end loop;
1603
1604          New_Line (File);
1605       end if;
1606
1607       F := 0;
1608       L := Char_Pos_Set_Len - 1;
1609
1610       Put      (File, Array_Img ("P", "Natural", Range_Img (F, L)));
1611       New_Line (File);
1612
1613       for J in F .. L loop
1614          Put (File, Image (Get_Char_Pos (J)), 1, 0, 1, F, L, J);
1615       end loop;
1616
1617       New_Line (File);
1618
1619       case Opt is
1620          when CPU_Time =>
1621             Put_Int_Matrix
1622               (File,
1623                Array_Img ("T1", Type_Img (NV),
1624                           Range_Img (0, T1_Len - 1),
1625                           Range_Img (0, T2_Len - 1, Type_Img (256))),
1626                T1, T1_Len, T2_Len);
1627
1628          when Memory_Space =>
1629             Put_Int_Matrix
1630               (File,
1631                Array_Img ("T1", Type_Img (NV),
1632                           Range_Img (0, T1_Len - 1)),
1633                T1, T1_Len, 0);
1634       end case;
1635
1636       New_Line (File);
1637
1638       case Opt is
1639          when CPU_Time =>
1640             Put_Int_Matrix
1641               (File,
1642                Array_Img ("T2", Type_Img (NV),
1643                           Range_Img (0, T1_Len - 1),
1644                           Range_Img (0, T2_Len - 1, Type_Img (256))),
1645                T2, T1_Len, T2_Len);
1646
1647          when Memory_Space =>
1648             Put_Int_Matrix
1649               (File,
1650                Array_Img ("T2", Type_Img (NV),
1651                           Range_Img (0, T1_Len - 1)),
1652                T2, T1_Len, 0);
1653       end case;
1654
1655       New_Line (File);
1656
1657       Put_Int_Vector
1658         (File,
1659          Array_Img ("G", Type_Img (NK),
1660                     Range_Img (0, G_Len - 1)),
1661          G, G_Len);
1662       New_Line (File);
1663
1664       Put      (File, "   function Hash (S : String) return Natural is");
1665       New_Line (File);
1666       Put      (File, "      F : constant Natural := S'First - 1;");
1667       New_Line (File);
1668       Put      (File, "      L : constant Natural := S'Length;");
1669       New_Line (File);
1670       Put      (File, "      F1, F2 : Natural := 0;");
1671       New_Line (File);
1672
1673       Put (File, "      J : ");
1674
1675       case Opt is
1676          when CPU_Time =>
1677             Put (File, Type_Img (256));
1678          when Memory_Space =>
1679             Put (File, "Natural");
1680       end case;
1681
1682       Put (File, ";");
1683       New_Line (File);
1684
1685       Put      (File, "   begin");
1686       New_Line (File);
1687       Put      (File, "      for K in P'Range loop");
1688       New_Line (File);
1689       Put      (File, "         exit when L < P (K);");
1690       New_Line (File);
1691       Put      (File, "         J  := ");
1692
1693       case Opt is
1694          when CPU_Time =>
1695             Put (File, "C");
1696          when Memory_Space =>
1697             Put (File, "Character'Pos");
1698       end case;
1699
1700       Put      (File, " (S (P (K) + F));");
1701       New_Line (File);
1702
1703       Put (File, "         F1 := (F1 + Natural (T1 (K");
1704
1705       if Opt = CPU_Time then
1706          Put (File, ", J");
1707       end if;
1708
1709       Put (File, "))");
1710
1711       if Opt = Memory_Space then
1712          Put (File, " * J");
1713       end if;
1714
1715       Put      (File, ") mod ");
1716       Put      (File, Image (NV));
1717       Put      (File, ";");
1718       New_Line (File);
1719
1720       Put (File, "         F2 := (F2 + Natural (T2 (K");
1721
1722       if Opt = CPU_Time then
1723          Put (File, ", J");
1724       end if;
1725
1726       Put (File, "))");
1727
1728       if Opt = Memory_Space then
1729          Put (File, " * J");
1730       end if;
1731
1732       Put      (File, ") mod ");
1733       Put      (File, Image (NV));
1734       Put      (File, ";");
1735       New_Line (File);
1736
1737       Put      (File, "      end loop;");
1738       New_Line (File);
1739
1740       Put      (File,
1741                 "      return (Natural (G (F1)) + Natural (G (F2))) mod ");
1742
1743       Put      (File, Image (NK));
1744       Put      (File, ";");
1745       New_Line (File);
1746       Put      (File, "   end Hash;");
1747       New_Line (File);
1748       New_Line (File);
1749       Put      (File, "end ");
1750       Put      (File, Pkg_Name);
1751       Put      (File, ";");
1752       New_Line (File);
1753
1754       if not Use_Stdout then
1755          Close (File, Status);
1756
1757          if not Status then
1758             raise Device_Error;
1759          end if;
1760       end if;
1761    end Produce;
1762
1763    ---------
1764    -- Put --
1765    ---------
1766
1767    procedure Put (File : File_Descriptor; Str : String) is
1768       Len : constant Natural := Str'Length;
1769    begin
1770       for J in Str'Range loop
1771          pragma Assert (Str (J) /= ASCII.NUL);
1772          null;
1773       end loop;
1774
1775       if Write (File, Str'Address, Len) /= Len then
1776          raise Program_Error;
1777       end if;
1778    end Put;
1779
1780    ---------
1781    -- Put --
1782    ---------
1783
1784    procedure Put
1785      (F  : File_Descriptor;
1786       S  : String;
1787       F1 : Natural;
1788       L1 : Natural;
1789       C1 : Natural;
1790       F2 : Natural;
1791       L2 : Natural;
1792       C2 : Natural)
1793    is
1794       Len : constant Natural := S'Length;
1795
1796       procedure Flush;
1797       --  Write current line, followed by LF
1798
1799       -----------
1800       -- Flush --
1801       -----------
1802
1803       procedure Flush is
1804       begin
1805          Put (F, Line (1 .. Last));
1806          New_Line (F);
1807          Last := 0;
1808       end Flush;
1809
1810    --  Start of processing for Put
1811
1812    begin
1813       if C1 = F1 and then C2 = F2 then
1814          Last := 0;
1815       end if;
1816
1817       if Last + Len + 3 >= Max then
1818          Flush;
1819       end if;
1820
1821       if Last = 0 then
1822          Add ("     ");
1823
1824          if F1 <= L1 then
1825             if C1 = F1 and then C2 = F2 then
1826                Add ('(');
1827
1828                if F1 = L1 then
1829                   Add ("0 .. 0 => ");
1830                end if;
1831
1832             else
1833                Add (' ');
1834             end if;
1835          end if;
1836       end if;
1837
1838       if C2 = F2 then
1839          Add ('(');
1840
1841          if F2 = L2 then
1842             Add ("0 .. 0 => ");
1843          end if;
1844
1845       else
1846          Add (' ');
1847       end if;
1848
1849       Add (S);
1850
1851       if C2 = L2 then
1852          Add (')');
1853
1854          if F1 > L1 then
1855             Add (';');
1856             Flush;
1857
1858          elsif C1 /= L1 then
1859             Add (',');
1860             Flush;
1861
1862          else
1863             Add (')');
1864             Add (';');
1865             Flush;
1866          end if;
1867
1868       else
1869          Add (',');
1870       end if;
1871    end Put;
1872
1873    ---------------
1874    -- Put_Edges --
1875    ---------------
1876
1877    procedure Put_Edges (File  : File_Descriptor; Title : String) is
1878       E  : Edge_Type;
1879       F1 : constant Natural := 1;
1880       L1 : constant Natural := Edges_Len - 1;
1881       M  : constant Natural := Max / 5;
1882
1883    begin
1884       Put (File, Title);
1885       New_Line (File);
1886
1887       --  Edges valid range is 1 .. Edge_Len - 1
1888
1889       for J in F1 .. L1 loop
1890          E := Get_Edges (J);
1891          Put (File, Image (J, M),     F1, L1, J, 1, 4, 1);
1892          Put (File, Image (E.X, M),   F1, L1, J, 1, 4, 2);
1893          Put (File, Image (E.Y, M),   F1, L1, J, 1, 4, 3);
1894          Put (File, Image (E.Key, M), F1, L1, J, 1, 4, 4);
1895       end loop;
1896    end Put_Edges;
1897
1898    ----------------------
1899    -- Put_Initial_Keys --
1900    ----------------------
1901
1902    procedure Put_Initial_Keys (File : File_Descriptor; Title : String) is
1903       F1 : constant Natural := 0;
1904       L1 : constant Natural := NK - 1;
1905       M  : constant Natural := Max / 5;
1906       K  : Key_Type;
1907
1908    begin
1909       Put (File, Title);
1910       New_Line (File);
1911
1912       for J in F1 .. L1 loop
1913          K := Get_Key (J);
1914          Put (File, Image (J, M),           F1, L1, J, 1, 3, 1);
1915          Put (File, Image (K.Edge, M),      F1, L1, J, 1, 3, 2);
1916          Put (File, Trim_Trailing_Nuls (WT.Table (Initial (J)).all),
1917                     F1, L1, J, 1, 3, 3);
1918       end loop;
1919    end Put_Initial_Keys;
1920
1921    --------------------
1922    -- Put_Int_Matrix --
1923    --------------------
1924
1925    procedure Put_Int_Matrix
1926      (File   : File_Descriptor;
1927       Title  : String;
1928       Table  : Integer;
1929       Len_1  : Natural;
1930       Len_2  : Natural)
1931    is
1932       F1 : constant Integer := 0;
1933       L1 : constant Integer := Len_1 - 1;
1934       F2 : constant Integer := 0;
1935       L2 : constant Integer := Len_2 - 1;
1936       Ix : Natural;
1937
1938    begin
1939       Put (File, Title);
1940       New_Line (File);
1941
1942       if Len_2 = 0 then
1943          for J in F1 .. L1 loop
1944             Ix := IT.Table (Table + J);
1945             Put (File, Image (Ix), 1, 0, 1, F1, L1, J);
1946          end loop;
1947
1948       else
1949          for J in F1 .. L1 loop
1950             for K in F2 .. L2 loop
1951                Ix := IT.Table (Table + J + K * Len_1);
1952                Put (File, Image (Ix), F1, L1, J, F2, L2, K);
1953             end loop;
1954          end loop;
1955       end if;
1956    end Put_Int_Matrix;
1957
1958    --------------------
1959    -- Put_Int_Vector --
1960    --------------------
1961
1962    procedure Put_Int_Vector
1963      (File   : File_Descriptor;
1964       Title  : String;
1965       Vector : Integer;
1966       Length : Natural)
1967    is
1968       F2 : constant Natural := 0;
1969       L2 : constant Natural := Length - 1;
1970
1971    begin
1972       Put (File, Title);
1973       New_Line (File);
1974
1975       for J in F2 .. L2 loop
1976          Put (File, Image (IT.Table (Vector + J)), 1, 0, 1, F2, L2, J);
1977       end loop;
1978    end Put_Int_Vector;
1979
1980    ----------------------
1981    -- Put_Reduced_Keys --
1982    ----------------------
1983
1984    procedure Put_Reduced_Keys (File : File_Descriptor; Title : String) is
1985       F1 : constant Natural := 0;
1986       L1 : constant Natural := NK - 1;
1987       M  : constant Natural := Max / 5;
1988       K  : Key_Type;
1989
1990    begin
1991       Put (File, Title);
1992       New_Line (File);
1993
1994       for J in F1 .. L1 loop
1995          K := Get_Key (J);
1996          Put (File, Image (J, M),           F1, L1, J, 1, 3, 1);
1997          Put (File, Image (K.Edge, M),      F1, L1, J, 1, 3, 2);
1998          Put (File, Trim_Trailing_Nuls (WT.Table (Reduced (J)).all),
1999                     F1, L1, J, 1, 3, 3);
2000       end loop;
2001    end Put_Reduced_Keys;
2002
2003    -----------------------
2004    -- Put_Used_Char_Set --
2005    -----------------------
2006
2007    procedure Put_Used_Char_Set (File : File_Descriptor; Title : String) is
2008       F : constant Natural := Character'Pos (Character'First);
2009       L : constant Natural := Character'Pos (Character'Last);
2010
2011    begin
2012       Put (File, Title);
2013       New_Line (File);
2014
2015       for J in Character'Range loop
2016          Put
2017            (File, Image (Get_Used_Char (J)), 1, 0, 1, F, L, Character'Pos (J));
2018       end loop;
2019    end Put_Used_Char_Set;
2020
2021    ----------------------
2022    -- Put_Vertex_Table --
2023    ----------------------
2024
2025    procedure Put_Vertex_Table (File : File_Descriptor; Title : String) is
2026       F1 : constant Natural := 0;
2027       L1 : constant Natural := NV - 1;
2028       M  : constant Natural := Max / 4;
2029       V  : Vertex_Type;
2030
2031    begin
2032       Put (File, Title);
2033       New_Line (File);
2034
2035       for J in F1 .. L1 loop
2036          V := Get_Vertices (J);
2037          Put (File, Image (J, M),       F1, L1, J, 1, 3, 1);
2038          Put (File, Image (V.First, M), F1, L1, J, 1, 3, 2);
2039          Put (File, Image (V.Last, M),  F1, L1, J, 1, 3, 3);
2040       end loop;
2041    end Put_Vertex_Table;
2042
2043    ------------
2044    -- Random --
2045    ------------
2046
2047    procedure Random (Seed : in out Natural) is
2048
2049       --  Park & Miller Standard Minimal using Schrage's algorithm to avoid
2050       --  overflow: Xn+1 = 16807 * Xn mod (2 ** 31 - 1)
2051
2052       R : Natural;
2053       Q : Natural;
2054       X : Integer;
2055
2056    begin
2057       R := Seed mod 127773;
2058       Q := Seed / 127773;
2059       X := 16807 * R - 2836 * Q;
2060
2061       Seed := (if X < 0 then X + 2147483647 else X);
2062    end Random;
2063
2064    -------------
2065    -- Reduced --
2066    -------------
2067
2068    function Reduced (K : Key_Id) return Word_Id is
2069    begin
2070       return K + NK + 1;
2071    end Reduced;
2072
2073    -----------------
2074    -- Resize_Word --
2075    -----------------
2076
2077    procedure Resize_Word (W : in out Word_Type; Len : Natural) is
2078       S1 : constant String := W.all;
2079       S2 : String (1 .. Len) := (others => ASCII.NUL);
2080       L  : constant Natural := S1'Length;
2081    begin
2082       if L /= Len then
2083          Free_Word (W);
2084          S2 (1 .. L) := S1;
2085          W := New_Word (S2);
2086       end if;
2087    end Resize_Word;
2088
2089    --------------------------
2090    -- Select_Char_Position --
2091    --------------------------
2092
2093    procedure Select_Char_Position is
2094
2095       type Vertex_Table_Type is array (Natural range <>) of Vertex_Type;
2096
2097       procedure Build_Identical_Keys_Sets
2098         (Table : in out Vertex_Table_Type;
2099          Last  : in out Natural;
2100          Pos   : Natural);
2101       --  Build a list of keys subsets that are identical with the current
2102       --  position selection plus Pos. Once this routine is called, reduced
2103       --  words are sorted by subsets and each item (First, Last) in Sets
2104       --  defines the range of identical keys.
2105       --  Need comment saying exactly what Last is ???
2106
2107       function Count_Different_Keys
2108         (Table : Vertex_Table_Type;
2109          Last  : Natural;
2110          Pos   : Natural) return Natural;
2111       --  For each subset in Sets, count the number of different keys if we add
2112       --  Pos to the current position selection.
2113
2114       Sel_Position : IT.Table_Type (1 .. Max_Key_Len);
2115       Last_Sel_Pos : Natural := 0;
2116       Max_Sel_Pos  : Natural := 0;
2117
2118       -------------------------------
2119       -- Build_Identical_Keys_Sets --
2120       -------------------------------
2121
2122       procedure Build_Identical_Keys_Sets
2123         (Table : in out Vertex_Table_Type;
2124          Last  : in out Natural;
2125          Pos   : Natural)
2126       is
2127          S : constant Vertex_Table_Type := Table (Table'First .. Last);
2128          C : constant Natural           := Pos;
2129          --  Shortcuts (why are these not renames ???)
2130
2131          F : Integer;
2132          L : Integer;
2133          --  First and last words of a subset
2134
2135          Offset : Natural;
2136          --  GNAT.Heap_Sort assumes that the first array index is 1. Offset
2137          --  defines the translation to operate.
2138
2139          function Lt (L, R : Natural) return Boolean;
2140          procedure Move (From : Natural; To : Natural);
2141          --  Subprograms needed by GNAT.Heap_Sort_G
2142
2143          --------
2144          -- Lt --
2145          --------
2146
2147          function Lt (L, R : Natural) return Boolean is
2148             C     : constant Natural := Pos;
2149             Left  : Natural;
2150             Right : Natural;
2151
2152          begin
2153             if L = 0 then
2154                Left  := NK;
2155                Right := Offset + R;
2156             elsif R = 0 then
2157                Left  := Offset + L;
2158                Right := NK;
2159             else
2160                Left  := Offset + L;
2161                Right := Offset + R;
2162             end if;
2163
2164             return WT.Table (Left)(C) < WT.Table (Right)(C);
2165          end Lt;
2166
2167          ----------
2168          -- Move --
2169          ----------
2170
2171          procedure Move (From : Natural; To : Natural) is
2172             Target, Source : Natural;
2173
2174          begin
2175             if From = 0 then
2176                Source := NK;
2177                Target := Offset + To;
2178             elsif To = 0 then
2179                Source := Offset + From;
2180                Target := NK;
2181             else
2182                Source := Offset + From;
2183                Target := Offset + To;
2184             end if;
2185
2186             WT.Table (Target) := WT.Table (Source);
2187             WT.Table (Source) := null;
2188          end Move;
2189
2190          package Sorting is new GNAT.Heap_Sort_G (Move, Lt);
2191
2192       --  Start of processing for Build_Identical_Key_Sets
2193
2194       begin
2195          Last := 0;
2196
2197          --  For each subset in S, extract the new subsets we have by adding C
2198          --  in the position selection.
2199
2200          for J in S'Range loop
2201             if S (J).First = S (J).Last then
2202                F := S (J).First;
2203                L := S (J).Last;
2204                Last := Last + 1;
2205                Table (Last) := (F, L);
2206
2207             else
2208                Offset := Reduced (S (J).First) - 1;
2209                Sorting.Sort (S (J).Last - S (J).First + 1);
2210
2211                F := S (J).First;
2212                L := F;
2213                for N in S (J).First .. S (J).Last loop
2214
2215                   --  For the last item, close the last subset
2216
2217                   if N = S (J).Last then
2218                      Last := Last + 1;
2219                      Table (Last) := (F, N);
2220
2221                   --  Two contiguous words are identical when they have the
2222                   --  same Cth character.
2223
2224                   elsif WT.Table (Reduced (N))(C) =
2225                         WT.Table (Reduced (N + 1))(C)
2226                   then
2227                      L := N + 1;
2228
2229                   --  Find a new subset of identical keys. Store the current
2230                   --  one and create a new subset.
2231
2232                   else
2233                      Last := Last + 1;
2234                      Table (Last) := (F, L);
2235                      F := N + 1;
2236                      L := F;
2237                   end if;
2238                end loop;
2239             end if;
2240          end loop;
2241       end Build_Identical_Keys_Sets;
2242
2243       --------------------------
2244       -- Count_Different_Keys --
2245       --------------------------
2246
2247       function Count_Different_Keys
2248         (Table : Vertex_Table_Type;
2249          Last  : Natural;
2250          Pos   : Natural) return Natural
2251       is
2252          N : array (Character) of Natural;
2253          C : Character;
2254          T : Natural := 0;
2255
2256       begin
2257          --  For each subset, count the number of words that are still
2258          --  different when we include Pos in the position selection. Only
2259          --  focus on this position as the other positions already produce
2260          --  identical keys.
2261
2262          for S in 1 .. Last loop
2263
2264             --  Count the occurrences of the different characters
2265
2266             N := (others => 0);
2267             for K in Table (S).First .. Table (S).Last loop
2268                C := WT.Table (Reduced (K))(Pos);
2269                N (C) := N (C) + 1;
2270             end loop;
2271
2272             --  Update the number of different keys. Each character used
2273             --  denotes a different key.
2274
2275             for J in N'Range loop
2276                if N (J) > 0 then
2277                   T := T + 1;
2278                end if;
2279             end loop;
2280          end loop;
2281
2282          return T;
2283       end Count_Different_Keys;
2284
2285    --  Start of processing for Select_Char_Position
2286
2287    begin
2288       --  Initialize the reduced words set
2289
2290       for K in 0 .. NK - 1 loop
2291          WT.Table (Reduced (K)) := New_Word (WT.Table (Initial (K)).all);
2292       end loop;
2293
2294       declare
2295          Differences          : Natural;
2296          Max_Differences      : Natural := 0;
2297          Old_Differences      : Natural;
2298          Max_Diff_Sel_Pos     : Natural := 0; -- init to kill warning
2299          Max_Diff_Sel_Pos_Idx : Natural := 0; -- init to kill warning
2300          Same_Keys_Sets_Table : Vertex_Table_Type (1 .. NK);
2301          Same_Keys_Sets_Last  : Natural := 1;
2302
2303       begin
2304          for C in Sel_Position'Range loop
2305             Sel_Position (C) := C;
2306          end loop;
2307
2308          Same_Keys_Sets_Table (1) := (0, NK - 1);
2309
2310          loop
2311             --  Preserve maximum number of different keys and check later on
2312             --  that this value is strictly incrementing. Otherwise, it means
2313             --  that two keys are strictly identical.
2314
2315             Old_Differences := Max_Differences;
2316
2317             --  The first position should not exceed the minimum key length.
2318             --  Otherwise, we may end up with an empty word once reduced.
2319
2320             Max_Sel_Pos :=
2321               (if Last_Sel_Pos = 0 then Min_Key_Len else Max_Key_Len);
2322
2323             --  Find which position increases more the number of differences
2324
2325             for J in Last_Sel_Pos + 1 .. Max_Sel_Pos loop
2326                Differences := Count_Different_Keys
2327                  (Same_Keys_Sets_Table,
2328                   Same_Keys_Sets_Last,
2329                   Sel_Position (J));
2330
2331                if Verbose then
2332                   Put (Output,
2333                        "Selecting position" & Sel_Position (J)'Img &
2334                          " results in" & Differences'Img &
2335                          " differences");
2336                   New_Line (Output);
2337                end if;
2338
2339                if Differences > Max_Differences then
2340                   Max_Differences      := Differences;
2341                   Max_Diff_Sel_Pos     := Sel_Position (J);
2342                   Max_Diff_Sel_Pos_Idx := J;
2343                end if;
2344             end loop;
2345
2346             if Old_Differences = Max_Differences then
2347                raise Program_Error with "some keys are identical";
2348             end if;
2349
2350             --  Insert selected position and sort Sel_Position table
2351
2352             Last_Sel_Pos := Last_Sel_Pos + 1;
2353             Sel_Position (Last_Sel_Pos + 1 .. Max_Diff_Sel_Pos_Idx) :=
2354               Sel_Position (Last_Sel_Pos .. Max_Diff_Sel_Pos_Idx - 1);
2355             Sel_Position (Last_Sel_Pos) := Max_Diff_Sel_Pos;
2356
2357             for P in 1 .. Last_Sel_Pos - 1 loop
2358                if Max_Diff_Sel_Pos < Sel_Position (P) then
2359                   Sel_Position (P + 1 .. Last_Sel_Pos) :=
2360                     Sel_Position (P .. Last_Sel_Pos - 1);
2361                   Sel_Position (P) := Max_Diff_Sel_Pos;
2362                   exit;
2363                end if;
2364             end loop;
2365
2366             exit when Max_Differences = NK;
2367
2368             Build_Identical_Keys_Sets
2369               (Same_Keys_Sets_Table,
2370                Same_Keys_Sets_Last,
2371                Max_Diff_Sel_Pos);
2372
2373             if Verbose then
2374                Put (Output,
2375                     "Selecting position" & Max_Diff_Sel_Pos'Img &
2376                       " results in" & Max_Differences'Img &
2377                       " differences");
2378                New_Line (Output);
2379                Put (Output, "--");
2380                New_Line (Output);
2381                for J in 1 .. Same_Keys_Sets_Last loop
2382                   for K in
2383                     Same_Keys_Sets_Table (J).First ..
2384                     Same_Keys_Sets_Table (J).Last
2385                   loop
2386                      Put (Output,
2387                           Trim_Trailing_Nuls (WT.Table (Reduced (K)).all));
2388                      New_Line (Output);
2389                   end loop;
2390                   Put (Output, "--");
2391                   New_Line (Output);
2392                end loop;
2393             end if;
2394          end loop;
2395       end;
2396
2397       Char_Pos_Set_Len := Last_Sel_Pos;
2398       Char_Pos_Set := Allocate (Char_Pos_Set_Len);
2399
2400       for C in 1 .. Last_Sel_Pos loop
2401          Set_Char_Pos (C - 1, Sel_Position (C));
2402       end loop;
2403    end Select_Char_Position;
2404
2405    --------------------------
2406    -- Select_Character_Set --
2407    --------------------------
2408
2409    procedure Select_Character_Set is
2410       Last : Natural := 0;
2411       Used : array (Character) of Boolean := (others => False);
2412       Char : Character;
2413
2414    begin
2415       for J in 0 .. NK - 1 loop
2416          for K in 0 .. Char_Pos_Set_Len - 1 loop
2417             Char := WT.Table (Initial (J))(Get_Char_Pos (K));
2418             exit when Char = ASCII.NUL;
2419             Used (Char) := True;
2420          end loop;
2421       end loop;
2422
2423       Used_Char_Set_Len := 256;
2424       Used_Char_Set := Allocate (Used_Char_Set_Len);
2425
2426       for J in Used'Range loop
2427          if Used (J) then
2428             Set_Used_Char (J, Last);
2429             Last := Last + 1;
2430          else
2431             Set_Used_Char (J, 0);
2432          end if;
2433       end loop;
2434    end Select_Character_Set;
2435
2436    ------------------
2437    -- Set_Char_Pos --
2438    ------------------
2439
2440    procedure Set_Char_Pos (P : Natural; Item : Natural) is
2441       N : constant Natural := Char_Pos_Set + P;
2442    begin
2443       IT.Table (N) := Item;
2444    end Set_Char_Pos;
2445
2446    ---------------
2447    -- Set_Edges --
2448    ---------------
2449
2450    procedure Set_Edges (F : Natural; Item : Edge_Type) is
2451       N : constant Natural := Edges + (F * Edge_Size);
2452    begin
2453       IT.Table (N)     := Item.X;
2454       IT.Table (N + 1) := Item.Y;
2455       IT.Table (N + 2) := Item.Key;
2456    end Set_Edges;
2457
2458    ---------------
2459    -- Set_Graph --
2460    ---------------
2461
2462    procedure Set_Graph (N : Natural; Item : Integer) is
2463    begin
2464       IT.Table (G + N) := Item;
2465    end Set_Graph;
2466
2467    -------------
2468    -- Set_Key --
2469    -------------
2470
2471    procedure Set_Key (N : Key_Id; Item : Key_Type) is
2472    begin
2473       IT.Table (Keys + N) := Item.Edge;
2474    end Set_Key;
2475
2476    ---------------
2477    -- Set_Table --
2478    ---------------
2479
2480    procedure Set_Table (T : Integer; X, Y : Natural; Item : Natural) is
2481       N : constant Natural := T + ((Y * T1_Len) + X);
2482    begin
2483       IT.Table (N) := Item;
2484    end Set_Table;
2485
2486    -------------------
2487    -- Set_Used_Char --
2488    -------------------
2489
2490    procedure Set_Used_Char (C : Character; Item : Natural) is
2491       N : constant Natural := Used_Char_Set + Character'Pos (C);
2492    begin
2493       IT.Table (N) := Item;
2494    end Set_Used_Char;
2495
2496    ------------------
2497    -- Set_Vertices --
2498    ------------------
2499
2500    procedure Set_Vertices (F : Natural; Item : Vertex_Type) is
2501       N : constant Natural := Vertices + (F * Vertex_Size);
2502    begin
2503       IT.Table (N)     := Item.First;
2504       IT.Table (N + 1) := Item.Last;
2505    end Set_Vertices;
2506
2507    ---------
2508    -- Sum --
2509    ---------
2510
2511    function Sum
2512      (Word  : Word_Type;
2513       Table : Table_Id;
2514       Opt   : Optimization) return Natural
2515    is
2516       S : Natural := 0;
2517       R : Natural;
2518
2519    begin
2520       case Opt is
2521          when CPU_Time =>
2522             for J in 0 .. T1_Len - 1 loop
2523                exit when Word (J + 1) = ASCII.NUL;
2524                R := Get_Table (Table, J, Get_Used_Char (Word (J + 1)));
2525                S := (S + R) mod NV;
2526             end loop;
2527
2528          when Memory_Space =>
2529             for J in 0 .. T1_Len - 1 loop
2530                exit when Word (J + 1) = ASCII.NUL;
2531                R := Get_Table (Table, J, 0);
2532                S := (S + R * Character'Pos (Word (J + 1))) mod NV;
2533             end loop;
2534       end case;
2535
2536       return S;
2537    end Sum;
2538
2539    ------------------------
2540    -- Trim_Trailing_Nuls --
2541    ------------------------
2542
2543    function Trim_Trailing_Nuls (Str : String) return String is
2544    begin
2545       for J in reverse Str'Range loop
2546          if Str (J) /= ASCII.NUL then
2547             return Str (Str'First .. J);
2548          end if;
2549       end loop;
2550
2551       return Str;
2552    end Trim_Trailing_Nuls;
2553
2554    ---------------
2555    -- Type_Size --
2556    ---------------
2557
2558    function Type_Size (L : Natural) return Natural is
2559    begin
2560       if L <= 2 ** 8 then
2561          return 8;
2562       elsif L <= 2 ** 16 then
2563          return 16;
2564       else
2565          return 32;
2566       end if;
2567    end Type_Size;
2568
2569    -----------
2570    -- Value --
2571    -----------
2572
2573    function Value
2574      (Name : Table_Name;
2575       J    : Natural;
2576       K    : Natural := 0) return Natural
2577    is
2578    begin
2579       case Name is
2580          when Character_Position =>
2581             return Get_Char_Pos (J);
2582
2583          when Used_Character_Set =>
2584             return Get_Used_Char (Character'Val (J));
2585
2586          when Function_Table_1 =>
2587             return Get_Table (T1, J, K);
2588
2589          when  Function_Table_2 =>
2590             return Get_Table (T2, J, K);
2591
2592          when Graph_Table =>
2593             return Get_Graph (J);
2594
2595       end case;
2596    end Value;
2597
2598 end GNAT.Perfect_Hash_Generators;