isl_map_subtract.c

   1 /*
   2  * Copyright 2008-2009 Katholieke Universiteit Leuven
   3  *
   4  * Use of this software is governed by the GNU LGPLv2.1 license
   5  *
   6  * Written by Sven Verdoolaege, K.U.Leuven, Departement
   7  * Computerwetenschappen, Celestijnenlaan 200A, B-3001 Leuven, Belgium
   8  */
   9
  10 #include "isl_seq.h"
  11 #include "isl_set.h"
  12 #include "isl_map.h"
  13 #include "isl_map_private.h"
  14 #include "isl_tab.h"
  15
  16 /* Add all constraints of bmap to tab.  The equalities of bmap
  17  * are added as a pair of inequalities.
  18  */
  19 static int tab_add_constraints(struct isl_tab *tab,
  20         __isl_keep isl_basic_map *bmap)
  21 {
  22         int i;
  23         unsigned total;
  24
  25         if (!tab || !bmap)
  26                 return -1;
  27
  28         total = isl_basic_map_total_dim(bmap);
  29
  30         if (isl_tab_extend_cons(tab, 2 * bmap->n_eq + bmap->n_ineq) < 0)
  31                 return -1;
  32
  33         for (i = 0; i < bmap->n_eq; ++i) {
  34                 if (isl_tab_add_ineq(tab, bmap->eq[i]) < 0)
  35                         return -1;
  36                 isl_seq_neg(bmap->eq[i], bmap->eq[i], 1 + total);
  37                 if (isl_tab_add_ineq(tab, bmap->eq[i]) < 0)
  38                         return -1;
  39                 isl_seq_neg(bmap->eq[i], bmap->eq[i], 1 + total);
  40                 if (tab->empty)
  41                         return 0;
  42         }
  43
  44         for (i = 0; i < bmap->n_ineq; ++i) {
  45                 if (isl_tab_add_ineq(tab, bmap->ineq[i]) < 0)
  46                         return -1;
  47                 if (tab->empty)
  48                         return 0;
  49         }
  50
  51         return 0;
  52 }
  53
  54 /* Add a specific constraint of bmap (or its opposite) to tab.
  55  * The position of the constraint is specified by "c", where
  56  * the equalities of bmap are counted twice, once for the inequality
  57  * that is equal to the equality, and once for its negation.
  58  */
  59 static int tab_add_constraint(struct isl_tab *tab,
  60         __isl_keep isl_basic_map *bmap, int c, int oppose)
  61 {
  62         unsigned total;
  63         int r;
  64
  65         if (!tab || !bmap)
  66                 return -1;
  67
  68         total = isl_basic_map_total_dim(bmap);
  69
  70         if (c < 2 * bmap->n_eq) {
  71                 if ((c % 2) != oppose)
  72                         isl_seq_neg(bmap->eq[c/2], bmap->eq[c/2], 1 + total);
  73                 if (oppose)
  74                         isl_int_sub_ui(bmap->eq[c/2][0], bmap->eq[c/2][0], 1);
  75                 r = isl_tab_add_ineq(tab, bmap->eq[c/2]);
  76                 if (oppose)
  77                         isl_int_add_ui(bmap->eq[c/2][0], bmap->eq[c/2][0], 1);
  78                 if ((c % 2) != oppose)
  79                         isl_seq_neg(bmap->eq[c/2], bmap->eq[c/2], 1 + total);
  80         } else {
  81                 c -= 2 * bmap->n_eq;
  82                 if (oppose) {
  83                         isl_seq_neg(bmap->ineq[c], bmap->ineq[c], 1 + total);
  84                         isl_int_sub_ui(bmap->ineq[c][0], bmap->ineq[c][0], 1);
  85                 }
  86                 r = isl_tab_add_ineq(tab, bmap->ineq[c]);
  87                 if (oppose) {
  88                         isl_int_add_ui(bmap->ineq[c][0], bmap->ineq[c][0], 1);
  89                         isl_seq_neg(bmap->ineq[c], bmap->ineq[c], 1 + total);
  90                 }
  91         }
  92
  93         return r;
  94 }
  95
  96 /* Freeze all constraints of tableau tab.
  97  */
  98 static int tab_freeze_constraints(struct isl_tab *tab)
  99 {
 100         int i;
 101
 102         for (i = 0; i < tab->n_con; ++i)
 103                 if (isl_tab_freeze_constraint(tab, i) < 0)
 104                         return -1;
 105
 106         return 0;
 107 }
 108
 109 /* Check for redundant constraints starting at offset.
 110  * Put the indices of the redundant constraints in index
 111  * and return the number of redundant constraints.
 112  */
 113 static int n_non_redundant(struct isl_tab *tab, int offset, int **index)
 114 {
 115         int i, n;
 116         int n_test = tab->n_con - offset;
 117
 118         if (isl_tab_detect_redundant(tab) < 0)
 119                 return -1;
 120
 121         if (!*index)
 122                 *index = isl_alloc_array(tab->mat->ctx, int, n_test);
 123         if (!*index)
 124                 return -1;
 125
 126         for (n = 0, i = 0; i < n_test; ++i) {
 127                 int r;
 128                 r = isl_tab_is_redundant(tab, offset + i);
 129                 if (r < 0)
 130                         return -1;
 131                 if (r)
 132                         continue;
 133                 (*index)[n++] = i;
 134         }
 135
 136         return n;
 137 }
 138
 139 /* basic_map_collect_diff calls add on each of the pieces of
 140  * the set difference between bmap and map until the add method
 141  * return a negative value.
 142  */
 143 struct isl_diff_collector {
 144         int (*add)(struct isl_diff_collector *dc,
 145                     __isl_take isl_basic_map *bmap);
 146 };
 147
 148 /* Compute the set difference between bmap and map and call
 149  * dc->add on each of the piece until this function returns
 150  * a negative value.
 151  * Return 0 on success and -1 on error.  dc->add returning
 152  * a negative value is treated as an error, but the calling
 153  * function can interpret the results based on the state of dc.
 154  *
 155  * Assumes that both bmap and map have known divs.
 156  *
 157  * The difference is computed by a backtracking algorithm.
 158  * Each level corresponds to a basic map in "map".
 159  * When a node in entered for the first time, we check
 160  * if the corresonding basic map intersect the current piece
 161  * of "bmap".  If not, we move to the next level.
 162  * Otherwise, we split the current piece into as many
 163  * pieces as there are non-redundant constraints of the current
 164  * basic map in the intersection.  Each of these pieces is
 165  * handled by a child of the current node.
 166  * In particular, if there are n non-redundant constraints,
 167  * then for each 0 <= i < n, a piece is cut off by adding
 168  * constraints 0 <= j < i and adding the opposite of constrain i.
 169  * If there are no non-redundant constraints, meaning that the current
 170  * piece is a subset of the current basic map, then we simply backtrack.
 171  *
 172  * In the leaves, we check if the remaining piece has any integer points
 173  * and if so, pass it along to dc->add.  As a special case, if nothing
 174  * has been removed when we end up in a leaf, we simply pass along
 175  * the original basic map.
 176  */
 177 static int basic_map_collect_diff(__isl_take isl_basic_map *bmap,
 178         __isl_take isl_map *map, struct isl_diff_collector *dc)
 179 {
 180         int i;
 181         int modified;
 182         int level;
 183         int init;
 184         int empty;
 185         struct isl_tab *tab = NULL;
 186         struct isl_tab_undo **snap = NULL;
 187         int *k = NULL;
 188         int *n = NULL;
 189         int **index = NULL;
 190
 191         empty = isl_basic_map_is_empty(bmap);
 192         if (empty) {
 193                 isl_basic_map_free(bmap);
 194                 isl_map_free(map);
 195                 return empty < 0 ? -1 : 0;
 196         }
 197
 198         bmap = isl_basic_map_cow(bmap);
 199         map = isl_map_cow(map);
 200
 201         if (!bmap || !map)
 202                 goto error;
 203
 204         snap = isl_alloc_array(map->ctx, struct isl_tab_undo *, map->n);
 205         k = isl_alloc_array(map->ctx, int, map->n);
 206         n = isl_alloc_array(map->ctx, int, map->n);
 207         index = isl_calloc_array(map->ctx, int *, map->n);
 208         if (!snap || !k || !n || !index)
 209                 goto error;
 210
 211         for (i = 0; i < map->n; ++i) {
 212                 bmap = isl_basic_map_align_divs(bmap, map->p[i]);
 213                 if (!bmap)
 214                         goto error;
 215         }
 216         for (i = 0; i < map->n; ++i) {
 217                 map->p[i] = isl_basic_map_align_divs(map->p[i], bmap);
 218                 if (!map->p[i])
 219                         goto error;
 220         }
 221
 222         tab = isl_tab_from_basic_map(bmap);
 223         if (isl_tab_track_bmap(tab, isl_basic_map_copy(bmap)) < 0)
 224                 goto error;
 225
 226         modified = 0;
 227         level = 0;
 228         init = 1;
 229
 230         while (level >= 0) {
 231                 if (level >= map->n) {
 232                         int empty;
 233                         struct isl_basic_map *bm;
 234                         if (!modified) {
 235                                 if (dc->add(dc, isl_basic_map_copy(bmap)) < 0)
 236                                         goto error;
 237                                 break;
 238                         }
 239                         bm = isl_basic_map_copy(tab->bmap);
 240                         bm = isl_basic_map_cow(bm);
 241                         bm = isl_basic_map_update_from_tab(bm, tab);
 242                         bm = isl_basic_map_simplify(bm);
 243                         bm = isl_basic_map_finalize(bm);
 244                         empty = isl_basic_map_is_empty(bm);
 245                         if (empty)
 246                                 isl_basic_map_free(bm);
 247                         else if (dc->add(dc, bm) < 0)
 248                                 goto error;
 249                         if (empty < 0)
 250                                 goto error;
 251                         level--;
 252                         init = 0;
 253                         continue;
 254                 }
 255                 if (init) {
 256                         int offset = tab->n_con;
 257                         snap[level] = isl_tab_snap(tab);
 258                         if (tab_freeze_constraints(tab) < 0)
 259                                 goto error;
 260                         if (tab_add_constraints(tab, map->p[level]) < 0)
 261                                 goto error;
 262                         k[level] = 0;
 263                         n[level] = 0;
 264                         if (tab->empty) {
 265                                 if (isl_tab_rollback(tab, snap[level]) < 0)
 266                                         goto error;
 267                                 level++;
 268                                 continue;
 269                         }
 270                         modified = 1;
 271                         n[level] = n_non_redundant(tab, offset, &index[level]);
 272                         if (n[level] < 0)
 273                                 goto error;
 274                         if (n[level] == 0) {
 275                                 level--;
 276                                 init = 0;
 277                                 continue;
 278                         }
 279                         if (isl_tab_rollback(tab, snap[level]) < 0)
 280                                 goto error;
 281                         if (tab_add_constraint(tab, map->p[level],
 282                                                 index[level][0], 1) < 0)
 283                                 goto error;
 284                         level++;
 285                         continue;
 286                 } else {
 287                         if (k[level] + 1 >= n[level]) {
 288                                 level--;
 289                                 continue;
 290                         }
 291                         if (isl_tab_rollback(tab, snap[level]) < 0)
 292                                 goto error;
 293                         if (tab_add_constraint(tab, map->p[level],
 294                                                 index[level][k[level]], 0) < 0)
 295                                 goto error;
 296                         snap[level] = isl_tab_snap(tab);
 297                         k[level]++;
 298                         if (tab_add_constraint(tab, map->p[level],
 299                                                 index[level][k[level]], 1) < 0)
 300                                 goto error;
 301                         level++;
 302                         init = 1;
 303                         continue;
 304                 }
 305         }
 306
 307         isl_tab_free(tab);
 308         free(snap);
 309         free(n);
 310         free(k);
 311         for (i = 0; index && i < map->n; ++i)
 312                 free(index[i]);
 313         free(index);
 314
 315         isl_basic_map_free(bmap);
 316         isl_map_free(map);
 317
 318         return 0;
 319 error:
 320         isl_tab_free(tab);
 321         free(snap);
 322         free(n);
 323         free(k);
 324         for (i = 0; index && i < map->n; ++i)
 325                 free(index[i]);
 326         free(index);
 327         isl_basic_map_free(bmap);
 328         isl_map_free(map);
 329         return -1;
 330 }
 331
 332 /* A diff collector that actually collects all parts of the
 333  * set difference in the field diff.
 334  */
 335 struct isl_subtract_diff_collector {
 336         struct isl_diff_collector dc;
 337         struct isl_map *diff;
 338 };
 339
 340 /* isl_subtract_diff_collector callback.
 341  */
 342 static int basic_map_subtract_add(struct isl_diff_collector *dc,
 343                             __isl_take isl_basic_map *bmap)
 344 {
 345         struct isl_subtract_diff_collector *sdc;
 346         sdc = (struct isl_subtract_diff_collector *)dc;
 347
 348         sdc->diff = isl_map_union_disjoint(sdc->diff,
 349                         isl_map_from_basic_map(bmap));
 350
 351         return sdc->diff ? 0 : -1;
 352 }
 353
 354 /* Return the set difference between bmap and map.
 355  */
 356 static __isl_give isl_map *basic_map_subtract(__isl_take isl_basic_map *bmap,
 357         __isl_take isl_map *map)
 358 {
 359         struct isl_subtract_diff_collector sdc;
 360         sdc.dc.add = &basic_map_subtract_add;
 361         sdc.diff = isl_map_empty_like_basic_map(bmap);
 362         if (basic_map_collect_diff(bmap, map, &sdc.dc) < 0) {
 363                 isl_map_free(sdc.diff);
 364                 sdc.diff = NULL;
 365         }
 366         return sdc.diff;
 367 }
 368
 369 /* Return the set difference between map1 and map2.
 370  * (U_i A_i) \ (U_j B_j) is computed as U_i (A_i \ (U_j B_j))
 371  */
 372 struct isl_map *isl_map_subtract(struct isl_map *map1, struct isl_map *map2)
 373 {
 374         int i;
 375         struct isl_map *diff;
 376
 377         if (!map1 || !map2)
 378                 goto error;
 379
 380         isl_assert(map1->ctx, isl_dim_equal(map1->dim, map2->dim), goto error);
 381
 382         if (isl_map_is_empty(map2)) {
 383                 isl_map_free(map2);
 384                 return map1;
 385         }
 386
 387         map1 = isl_map_compute_divs(map1);
 388         map2 = isl_map_compute_divs(map2);
 389         if (!map1 || !map2)
 390                 goto error;
 391
 392         map1 = isl_map_remove_empty_parts(map1);
 393         map2 = isl_map_remove_empty_parts(map2);
 394
 395         diff = isl_map_empty_like(map1);
 396         for (i = 0; i < map1->n; ++i) {
 397                 struct isl_map *d;
 398                 d = basic_map_subtract(isl_basic_map_copy(map1->p[i]),
 399                                        isl_map_copy(map2));
 400                 if (ISL_F_ISSET(map1, ISL_MAP_DISJOINT))
 401                         diff = isl_map_union_disjoint(diff, d);
 402                 else
 403                         diff = isl_map_union(diff, d);
 404         }
 405
 406         isl_map_free(map1);
 407         isl_map_free(map2);
 408
 409         return diff;
 410 error:
 411         isl_map_free(map1);
 412         isl_map_free(map2);
 413         return NULL;
 414 }
 415
 416 struct isl_set *isl_set_subtract(struct isl_set *set1, struct isl_set *set2)
 417 {
 418         return (struct isl_set *)
 419                 isl_map_subtract(
 420                         (struct isl_map *)set1, (struct isl_map *)set2);
 421 }
 422
 423 /* A diff collector that aborts as soon as its add function is called,
 424  * setting empty to 0.
 425  */
 426 struct isl_is_empty_diff_collector {
 427         struct isl_diff_collector dc;
 428         int empty;
 429 };
 430
 431 /* isl_is_empty_diff_collector callback.
 432  */
 433 static int basic_map_is_empty_add(struct isl_diff_collector *dc,
 434                             __isl_take isl_basic_map *bmap)
 435 {
 436         struct isl_is_empty_diff_collector *edc;
 437         edc = (struct isl_is_empty_diff_collector *)dc;
 438
 439         edc->empty = 0;
 440
 441         isl_basic_map_free(bmap);
 442         return -1;
 443 }
 444
 445 /* Check if bmap \ map is empty by computing this set difference
 446  * and breaking off as soon as the difference is known to be non-empty.
 447  */
 448 static int basic_map_diff_is_empty(__isl_keep isl_basic_map *bmap,
 449         __isl_keep isl_map *map)
 450 {
 451         int r;
 452         struct isl_is_empty_diff_collector edc;
 453
 454         r = isl_basic_map_fast_is_empty(bmap);
 455         if (r)
 456                 return r;
 457
 458         edc.dc.add = &basic_map_is_empty_add;
 459         edc.empty = 1;
 460         r = basic_map_collect_diff(isl_basic_map_copy(bmap),
 461                                    isl_map_copy(map), &edc.dc);
 462         if (!edc.empty)
 463                 return 0;
 464
 465         return r < 0 ? -1 : 1;
 466 }
 467
 468 /* Check if map1 \ map2 is empty by checking if the set difference is empty
 469  * for each of the basic maps in map1.
 470  */
 471 static int map_diff_is_empty(__isl_keep isl_map *map1, __isl_keep isl_map *map2)
 472 {
 473         int i;
 474         int is_empty = 1;
 475
 476         if (!map1 || !map2)
 477                 return -1;
 478
 479         for (i = 0; i < map1->n; ++i) {
 480                 is_empty = basic_map_diff_is_empty(map1->p[i], map2);
 481                 if (is_empty < 0 || !is_empty)
 482                          break;
 483         }
 484
 485         return is_empty;
 486 }
 487
 488 /* Return 1 if "bmap" contains a single element.
 489  */
 490 int isl_basic_map_is_singleton(__isl_keep isl_basic_map *bmap)
 491 {
 492         if (!bmap)
 493                 return -1;
 494         if (bmap->n_div)
 495                 return 0;
 496         if (bmap->n_ineq)
 497                 return 0;
 498         return bmap->n_eq == isl_basic_map_total_dim(bmap);
 499 }
 500
 501 /* Return 1 if "map" contains a single element.
 502  */
 503 int isl_map_is_singleton(__isl_keep isl_map *map)
 504 {
 505         if (!map)
 506                 return -1;
 507         if (map->n != 1)
 508                 return 0;
 509
 510         return isl_basic_map_is_singleton(map->p[0]);
 511 }
 512
 513 /* Given a singleton basic map, extract the single element
 514  * as an isl_vec.
 515  */
 516 static __isl_give isl_vec *singleton_extract_point(__isl_keep isl_basic_map *bmap)
 517 {
 518         int i, j;
 519         unsigned dim;
 520         struct isl_vec *point;
 521         isl_int m;
 522
 523         if (!bmap)
 524                 return NULL;
 525
 526         dim = isl_basic_map_total_dim(bmap);
 527         isl_assert(bmap->ctx, bmap->n_eq == dim, return NULL);
 528         point = isl_vec_alloc(bmap->ctx, 1 + dim);
 529         if (!point)
 530                 return NULL;
 531
 532         isl_int_init(m);
 533
 534         isl_int_set_si(point->el[0], 1);
 535         for (j = 0; j < bmap->n_eq; ++j) {
 536                 int s;
 537                 int i = dim - 1 - j;
 538                 isl_assert(bmap->ctx,
 539                     isl_seq_first_non_zero(bmap->eq[j] + 1, i) == -1,
 540                     goto error);
 541                 isl_assert(bmap->ctx,
 542                     isl_int_is_one(bmap->eq[j][1 + i]) ||
 543                     isl_int_is_negone(bmap->eq[j][1 + i]),
 544                     goto error);
 545                 isl_assert(bmap->ctx,
 546                     isl_seq_first_non_zero(bmap->eq[j]+1+i+1, dim-i-1) == -1,
 547                     goto error);
 548
 549                 isl_int_gcd(m, point->el[0], bmap->eq[j][1 + i]);
 550                 isl_int_divexact(m, bmap->eq[j][1 + i], m);
 551                 isl_int_abs(m, m);
 552                 isl_seq_scale(point->el, point->el, m, 1 + i);
 553                 isl_int_divexact(m, point->el[0], bmap->eq[j][1 + i]);
 554                 isl_int_neg(m, m);
 555                 isl_int_mul(point->el[1 + i], m, bmap->eq[j][0]);
 556         }
 557
 558         isl_int_clear(m);
 559         return point;
 560 error:
 561         isl_int_clear(m);
 562         isl_vec_free(point);
 563         return NULL;
 564 }
 565
 566 /* Return 1 if "bmap" contains the point "point".
 567  * "bmap" is assumed to have known divs.
 568  * The point is first extended with the divs and then passed
 569  * to basic_map_contains.
 570  */
 571 static int basic_map_contains_point(__isl_keep isl_basic_map *bmap,
 572         __isl_keep isl_vec *point)
 573 {
 574         int i;
 575         struct isl_vec *vec;
 576         unsigned dim;
 577         int contains;
 578
 579         if (!bmap || !point)
 580                 return -1;
 581         if (bmap->n_div == 0)
 582                 return isl_basic_map_contains(bmap, point);
 583
 584         dim = isl_basic_map_total_dim(bmap) - bmap->n_div;
 585         vec = isl_vec_alloc(bmap->ctx, 1 + dim + bmap->n_div);
 586         if (!vec)
 587                 return -1;
 588
 589         isl_seq_cpy(vec->el, point->el, point->size);
 590         for (i = 0; i < bmap->n_div; ++i) {
 591                 isl_seq_inner_product(bmap->div[i] + 1, vec->el,
 592                                         1 + dim + i, &vec->el[1+dim+i]);
 593                 isl_int_fdiv_q(vec->el[1+dim+i], vec->el[1+dim+i],
 594                                 bmap->div[i][0]);
 595         }
 596
 597         contains = isl_basic_map_contains(bmap, vec);
 598
 599         isl_vec_free(vec);
 600         return contains;
 601 }
 602
 603 /* Return 1 is the singleton map "map1" is a subset of "map2",
 604  * i.e., if the single element of "map1" is also an element of "map2".
 605  */
 606 static int map_is_singleton_subset(__isl_keep isl_map *map1,
 607         __isl_keep isl_map *map2)
 608 {
 609         int i;
 610         int is_subset = 0;
 611         struct isl_vec *point;
 612
 613         if (!map1 || !map2)
 614                 return -1;
 615         if (map1->n != 1)
 616                 return -1;
 617
 618         point = singleton_extract_point(map1->p[0]);
 619         if (!point)
 620                 return -1;
 621
 622         for (i = 0; i < map2->n; ++i) {
 623                 is_subset = basic_map_contains_point(map2->p[i], point);
 624                 if (is_subset)
 625                         break;
 626         }
 627
 628         isl_vec_free(point);
 629         return is_subset;
 630 }
 631
 632 int isl_map_is_subset(struct isl_map *map1, struct isl_map *map2)
 633 {
 634         int is_subset = 0;
 635         struct isl_map *diff;
 636
 637         if (!map1 || !map2)
 638                 return -1;
 639
 640         if (isl_map_is_empty(map1))
 641                 return 1;
 642
 643         if (isl_map_is_empty(map2))
 644                 return 0;
 645
 646         if (isl_map_fast_is_universe(map2))
 647                 return 1;
 648
 649         map1 = isl_map_compute_divs(isl_map_copy(map1));
 650         map2 = isl_map_compute_divs(isl_map_copy(map2));
 651         if (isl_map_is_singleton(map1)) {
 652                 is_subset = map_is_singleton_subset(map1, map2);
 653                 isl_map_free(map1);
 654                 isl_map_free(map2);
 655                 return is_subset;
 656         }
 657         is_subset = map_diff_is_empty(map1, map2);
 658         isl_map_free(map1);
 659         isl_map_free(map2);
 660
 661         return is_subset;
 662 }
 663
 664 int isl_set_is_subset(struct isl_set *set1, struct isl_set *set2)
 665 {
 666         return isl_map_is_subset(
 667                         (struct isl_map *)set1, (struct isl_map *)set2);
 668 }
 669
 670 __isl_give isl_map *isl_map_make_disjoint(__isl_take isl_map *map)
 671 {
 672         int i;
 673         struct isl_subtract_diff_collector sdc;
 674         sdc.dc.add = &basic_map_subtract_add;
 675
 676         if (!map)
 677                 return NULL;
 678         if (ISL_F_ISSET(map, ISL_MAP_DISJOINT))
 679                 return map;
 680         if (map->n <= 1)
 681                 return map;
 682
 683         map = isl_map_compute_divs(map);
 684         map = isl_map_remove_empty_parts(map);
 685
 686         if (!map || map->n <= 1)
 687                 return map;
 688
 689         sdc.diff = isl_map_from_basic_map(isl_basic_map_copy(map->p[0]));
 690
 691         for (i = 1; i < map->n; ++i) {
 692                 struct isl_basic_map *bmap = isl_basic_map_copy(map->p[i]);
 693                 struct isl_map *copy = isl_map_copy(sdc.diff);
 694                 if (basic_map_collect_diff(bmap, copy, &sdc.dc) < 0) {
 695                         isl_map_free(sdc.diff);
 696                         sdc.diff = NULL;
 697                         break;
 698                 }
 699         }
 700
 701         isl_map_free(map);
 702
 703         return sdc.diff;
 704 }
 705
 706 __isl_give isl_set *isl_set_make_disjoint(__isl_take isl_set *set)
 707 {
 708         return (struct isl_set *)isl_map_make_disjoint((struct isl_map *)set);
 709 }