src/math/extrema.c

   1 /* PSPP - a program for statistical analysis.
   2    Copyright (C) 2008, 2011 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
  16
  17 #include <config.h>
  18
  19 #include "math/extrema.h"
  20
  21 #include <stdlib.h>
  22
  23 #include "data/case.h"
  24 #include "data/val-type.h"
  25 #include "libpspp/compiler.h"
  26 #include "libpspp/ll.h"
  27
  28 #include "gl/xalloc.h"
  29
  30 struct extrema
  31 {
  32   size_t capacity;
  33   size_t n;
  34   struct ll_list list;
  35
  36   ll_compare_func *cmp_func;
  37 };
  38
  39
  40 static int
  41 cmp_descending (const struct ll *a_, const struct ll *b_, void *aux UNUSED)
  42 {
  43   const struct extremum *a = ll_data (a_, struct extremum, ll);
  44   const struct extremum *b = ll_data (b_, struct extremum, ll);
  45
  46   if ( a->value > b->value) return -1;
  47
  48   return (a->value < b->value);
  49 }
  50
  51 static int
  52 cmp_ascending (const struct ll *a_, const struct ll *b_, void *aux UNUSED)
  53 {
  54   const struct extremum *a = ll_data (a_, struct extremum, ll);
  55   const struct extremum *b = ll_data (b_, struct extremum, ll);
  56
  57   if ( a->value < b->value) return -1;
  58
  59   return (a->value > b->value);
  60 }
  61
  62
  63 struct extrema *
  64 extrema_create (size_t n, enum extreme_end end)
  65 {
  66   struct extrema *extrema = xzalloc (sizeof *extrema);
  67   extrema->capacity = n;
  68
  69   if ( end == EXTREME_MAXIMA )
  70     extrema->cmp_func = cmp_descending;
  71   else
  72     extrema->cmp_func = cmp_ascending;
  73
  74   ll_init (&extrema->list);
  75
  76   return extrema;
  77 }
  78
  79 void
  80 extrema_destroy (struct extrema *extrema)
  81 {
  82   struct ll *ll = ll_head (&extrema->list);
  83
  84   while (ll != ll_null (&extrema->list))
  85     {
  86       struct extremum *e = ll_data (ll, struct extremum, ll);
  87
  88       ll = ll_next (ll);
  89       free (e);
  90     }
  91
  92   free (extrema);
  93 }
  94
  95
  96 void
  97 extrema_add (struct extrema *extrema, double val,
  98              double weight,
  99              casenumber location)
 100 {
 101   struct extremum *e = xzalloc (sizeof *e) ;
 102   e->value = val;
 103   e->location = location;
 104   e->weight = weight;
 105
 106   if ( val == SYSMIS)
 107     {
 108       free (e);
 109       return;
 110     }
 111
 112   ll_insert_ordered (ll_head (&extrema->list), ll_null (&extrema->list),
 113                        &e->ll,  extrema->cmp_func, NULL);
 114
 115   if ( extrema->n++ > extrema->capacity)
 116     {
 117       struct ll *tail = ll_tail (&extrema->list);
 118       struct extremum *et = ll_data (tail, struct extremum, ll);
 119
 120       ll_remove (tail);
 121
 122       free (et);
 123     }
 124 }
 125
 126
 127 const struct ll_list *
 128 extrema_list (const struct extrema *ex)
 129 {
 130   return &ex->list;
 131 }
 132
 133
 134 bool
 135 extrema_top (const struct extrema *ex, double *v)
 136 {
 137   const struct extremum  *top;
 138
 139   if ( ll_is_empty (&ex->list))
 140     return false;
 141
 142   top = (const struct extremum *)
 143     ll_data (ll_head(&ex->list), struct extremum, ll);
 144
 145   *v = top->value;
 146
 147   return true;
 148 }