2 * Copyright 2008-2009 Katholieke Universiteit Leuven
4 * Use of this software is governed by the GNU LGPLv2.1 license
6 * Written by Sven Verdoolaege, K.U.Leuven, Departement
7 * Computerwetenschappen, Celestijnenlaan 200A, B-3001 Leuven, Belgium
12 #include "isl_map_private.h"
16 #include "isl_equalities.h"
19 static struct isl_basic_set *uset_convex_hull_wrap_bounded(struct isl_set *set);
21 static void swap_ineq(struct isl_basic_map *bmap, unsigned i, unsigned j)
27 bmap->ineq[i] = bmap->ineq[j];
32 /* Return 1 if constraint c is redundant with respect to the constraints
33 * in bmap. If c is a lower [upper] bound in some variable and bmap
34 * does not have a lower [upper] bound in that variable, then c cannot
35 * be redundant and we do not need solve any lp.
37 int isl_basic_map_constraint_is_redundant(struct isl_basic_map **bmap,
38 isl_int *c, isl_int *opt_n, isl_int *opt_d)
40 enum isl_lp_result res;
47 total = isl_basic_map_total_dim(*bmap);
48 for (i = 0; i < total; ++i) {
50 if (isl_int_is_zero(c[1+i]))
52 sign = isl_int_sgn(c[1+i]);
53 for (j = 0; j < (*bmap)->n_ineq; ++j)
54 if (sign == isl_int_sgn((*bmap)->ineq[j][1+i]))
56 if (j == (*bmap)->n_ineq)
62 res = isl_basic_map_solve_lp(*bmap, 0, c, (*bmap)->ctx->one,
64 if (res == isl_lp_unbounded)
66 if (res == isl_lp_error)
68 if (res == isl_lp_empty) {
69 *bmap = isl_basic_map_set_to_empty(*bmap);
72 return !isl_int_is_neg(*opt_n);
75 int isl_basic_set_constraint_is_redundant(struct isl_basic_set **bset,
76 isl_int *c, isl_int *opt_n, isl_int *opt_d)
78 return isl_basic_map_constraint_is_redundant(
79 (struct isl_basic_map **)bset, c, opt_n, opt_d);
82 /* Compute the convex hull of a basic map, by removing the redundant
83 * constraints. If the minimal value along the normal of a constraint
84 * is the same if the constraint is removed, then the constraint is redundant.
86 * Alternatively, we could have intersected the basic map with the
87 * corresponding equality and the checked if the dimension was that
90 struct isl_basic_map *isl_basic_map_convex_hull(struct isl_basic_map *bmap)
97 bmap = isl_basic_map_gauss(bmap, NULL);
98 if (ISL_F_ISSET(bmap, ISL_BASIC_MAP_EMPTY))
100 if (ISL_F_ISSET(bmap, ISL_BASIC_MAP_NO_REDUNDANT))
102 if (bmap->n_ineq <= 1)
105 tab = isl_tab_from_basic_map(bmap);
106 tab = isl_tab_detect_implicit_equalities(tab);
107 if (isl_tab_detect_redundant(tab) < 0)
109 bmap = isl_basic_map_update_from_tab(bmap, tab);
111 ISL_F_SET(bmap, ISL_BASIC_MAP_NO_IMPLICIT);
112 ISL_F_SET(bmap, ISL_BASIC_MAP_NO_REDUNDANT);
116 isl_basic_map_free(bmap);
120 struct isl_basic_set *isl_basic_set_convex_hull(struct isl_basic_set *bset)
122 return (struct isl_basic_set *)
123 isl_basic_map_convex_hull((struct isl_basic_map *)bset);
126 /* Check if the set set is bound in the direction of the affine
127 * constraint c and if so, set the constant term such that the
128 * resulting constraint is a bounding constraint for the set.
130 static int uset_is_bound(struct isl_set *set, isl_int *c, unsigned len)
138 isl_int_init(opt_denom);
140 for (j = 0; j < set->n; ++j) {
141 enum isl_lp_result res;
143 if (ISL_F_ISSET(set->p[j], ISL_BASIC_SET_EMPTY))
146 res = isl_basic_set_solve_lp(set->p[j],
147 0, c, set->ctx->one, &opt, &opt_denom, NULL);
148 if (res == isl_lp_unbounded)
150 if (res == isl_lp_error)
152 if (res == isl_lp_empty) {
153 set->p[j] = isl_basic_set_set_to_empty(set->p[j]);
158 if (!isl_int_is_one(opt_denom))
159 isl_seq_scale(c, c, opt_denom, len);
160 if (first || isl_int_is_neg(opt))
161 isl_int_sub(c[0], c[0], opt);
165 isl_int_clear(opt_denom);
169 isl_int_clear(opt_denom);
173 /* Check if "c" is a direction that is independent of the previously found "n"
175 * If so, add it to the list, with the negative of the lower bound
176 * in the constant position, i.e., such that c corresponds to a bounding
177 * hyperplane (but not necessarily a facet).
178 * Assumes set "set" is bounded.
180 static int is_independent_bound(struct isl_set *set, isl_int *c,
181 struct isl_mat *dirs, int n)
186 isl_seq_cpy(dirs->row[n]+1, c+1, dirs->n_col-1);
188 int pos = isl_seq_first_non_zero(dirs->row[n]+1, dirs->n_col-1);
191 for (i = 0; i < n; ++i) {
193 pos_i = isl_seq_first_non_zero(dirs->row[i]+1, dirs->n_col-1);
198 isl_seq_elim(dirs->row[n]+1, dirs->row[i]+1, pos,
199 dirs->n_col-1, NULL);
200 pos = isl_seq_first_non_zero(dirs->row[n]+1, dirs->n_col-1);
206 is_bound = uset_is_bound(set, dirs->row[n], dirs->n_col);
211 isl_int *t = dirs->row[n];
212 for (k = n; k > i; --k)
213 dirs->row[k] = dirs->row[k-1];
219 /* Compute and return a maximal set of linearly independent bounds
220 * on the set "set", based on the constraints of the basic sets
223 static struct isl_mat *independent_bounds(struct isl_set *set)
226 struct isl_mat *dirs = NULL;
227 unsigned dim = isl_set_n_dim(set);
229 dirs = isl_mat_alloc(set->ctx, dim, 1+dim);
234 for (i = 0; n < dim && i < set->n; ++i) {
236 struct isl_basic_set *bset = set->p[i];
238 for (j = 0; n < dim && j < bset->n_eq; ++j) {
239 f = is_independent_bound(set, bset->eq[j], dirs, n);
245 for (j = 0; n < dim && j < bset->n_ineq; ++j) {
246 f = is_independent_bound(set, bset->ineq[j], dirs, n);
260 struct isl_basic_set *isl_basic_set_set_rational(struct isl_basic_set *bset)
265 if (ISL_F_ISSET(bset, ISL_BASIC_MAP_RATIONAL))
268 bset = isl_basic_set_cow(bset);
272 ISL_F_SET(bset, ISL_BASIC_MAP_RATIONAL);
274 return isl_basic_set_finalize(bset);
277 static struct isl_set *isl_set_set_rational(struct isl_set *set)
281 set = isl_set_cow(set);
284 for (i = 0; i < set->n; ++i) {
285 set->p[i] = isl_basic_set_set_rational(set->p[i]);
295 static struct isl_basic_set *isl_basic_set_add_equality(
296 struct isl_basic_set *bset, isl_int *c)
301 if (ISL_F_ISSET(bset, ISL_BASIC_SET_EMPTY))
304 isl_assert(bset->ctx, isl_basic_set_n_param(bset) == 0, goto error);
305 isl_assert(bset->ctx, bset->n_div == 0, goto error);
306 dim = isl_basic_set_n_dim(bset);
307 bset = isl_basic_set_cow(bset);
308 bset = isl_basic_set_extend(bset, 0, dim, 0, 1, 0);
309 i = isl_basic_set_alloc_equality(bset);
312 isl_seq_cpy(bset->eq[i], c, 1 + dim);
315 isl_basic_set_free(bset);
319 static struct isl_set *isl_set_add_equality(struct isl_set *set, isl_int *c)
323 set = isl_set_cow(set);
326 for (i = 0; i < set->n; ++i) {
327 set->p[i] = isl_basic_set_add_equality(set->p[i], c);
337 /* Given a union of basic sets, construct the constraints for wrapping
338 * a facet around one of its ridges.
339 * In particular, if each of n the d-dimensional basic sets i in "set"
340 * contains the origin, satisfies the constraints x_1 >= 0 and x_2 >= 0
341 * and is defined by the constraints
345 * then the resulting set is of dimension n*(1+d) and has as constraints
354 static struct isl_basic_set *wrap_constraints(struct isl_set *set)
356 struct isl_basic_set *lp;
360 unsigned dim, lp_dim;
365 dim = 1 + isl_set_n_dim(set);
368 for (i = 0; i < set->n; ++i) {
369 n_eq += set->p[i]->n_eq;
370 n_ineq += set->p[i]->n_ineq;
372 lp = isl_basic_set_alloc(set->ctx, 0, dim * set->n, 0, n_eq, n_ineq);
375 lp_dim = isl_basic_set_n_dim(lp);
376 k = isl_basic_set_alloc_equality(lp);
377 isl_int_set_si(lp->eq[k][0], -1);
378 for (i = 0; i < set->n; ++i) {
379 isl_int_set_si(lp->eq[k][1+dim*i], 0);
380 isl_int_set_si(lp->eq[k][1+dim*i+1], 1);
381 isl_seq_clr(lp->eq[k]+1+dim*i+2, dim-2);
383 for (i = 0; i < set->n; ++i) {
384 k = isl_basic_set_alloc_inequality(lp);
385 isl_seq_clr(lp->ineq[k], 1+lp_dim);
386 isl_int_set_si(lp->ineq[k][1+dim*i], 1);
388 for (j = 0; j < set->p[i]->n_eq; ++j) {
389 k = isl_basic_set_alloc_equality(lp);
390 isl_seq_clr(lp->eq[k], 1+dim*i);
391 isl_seq_cpy(lp->eq[k]+1+dim*i, set->p[i]->eq[j], dim);
392 isl_seq_clr(lp->eq[k]+1+dim*(i+1), dim*(set->n-i-1));
395 for (j = 0; j < set->p[i]->n_ineq; ++j) {
396 k = isl_basic_set_alloc_inequality(lp);
397 isl_seq_clr(lp->ineq[k], 1+dim*i);
398 isl_seq_cpy(lp->ineq[k]+1+dim*i, set->p[i]->ineq[j], dim);
399 isl_seq_clr(lp->ineq[k]+1+dim*(i+1), dim*(set->n-i-1));
405 /* Given a facet "facet" of the convex hull of "set" and a facet "ridge"
406 * of that facet, compute the other facet of the convex hull that contains
409 * We first transform the set such that the facet constraint becomes
413 * I.e., the facet lies in
417 * and on that facet, the constraint that defines the ridge is
421 * (This transformation is not strictly needed, all that is needed is
422 * that the ridge contains the origin.)
424 * Since the ridge contains the origin, the cone of the convex hull
425 * will be of the form
430 * with this second constraint defining the new facet.
431 * The constant a is obtained by settting x_1 in the cone of the
432 * convex hull to 1 and minimizing x_2.
433 * Now, each element in the cone of the convex hull is the sum
434 * of elements in the cones of the basic sets.
435 * If a_i is the dilation factor of basic set i, then the problem
436 * we need to solve is
449 * the constraints of each (transformed) basic set.
450 * If a = n/d, then the constraint defining the new facet (in the transformed
453 * -n x_1 + d x_2 >= 0
455 * In the original space, we need to take the same combination of the
456 * corresponding constraints "facet" and "ridge".
458 * Note that a is always finite, since we only apply the wrapping
459 * technique to a union of polytopes.
461 static isl_int *wrap_facet(struct isl_set *set, isl_int *facet, isl_int *ridge)
464 struct isl_mat *T = NULL;
465 struct isl_basic_set *lp = NULL;
467 enum isl_lp_result res;
471 set = isl_set_copy(set);
473 dim = 1 + isl_set_n_dim(set);
474 T = isl_mat_alloc(set->ctx, 3, dim);
477 isl_int_set_si(T->row[0][0], 1);
478 isl_seq_clr(T->row[0]+1, dim - 1);
479 isl_seq_cpy(T->row[1], facet, dim);
480 isl_seq_cpy(T->row[2], ridge, dim);
481 T = isl_mat_right_inverse(T);
482 set = isl_set_preimage(set, T);
486 lp = wrap_constraints(set);
487 obj = isl_vec_alloc(set->ctx, 1 + dim*set->n);
490 isl_int_set_si(obj->block.data[0], 0);
491 for (i = 0; i < set->n; ++i) {
492 isl_seq_clr(obj->block.data + 1 + dim*i, 2);
493 isl_int_set_si(obj->block.data[1 + dim*i+2], 1);
494 isl_seq_clr(obj->block.data + 1 + dim*i+3, dim-3);
498 res = isl_basic_set_solve_lp(lp, 0,
499 obj->block.data, set->ctx->one, &num, &den, NULL);
500 if (res == isl_lp_ok) {
501 isl_int_neg(num, num);
502 isl_seq_combine(facet, num, facet, den, ridge, dim);
507 isl_basic_set_free(lp);
509 isl_assert(set->ctx, res == isl_lp_ok, return NULL);
512 isl_basic_set_free(lp);
518 /* Given a set of d linearly independent bounding constraints of the
519 * convex hull of "set", compute the constraint of a facet of "set".
521 * We first compute the intersection with the first bounding hyperplane
522 * and remove the component corresponding to this hyperplane from
523 * other bounds (in homogeneous space).
524 * We then wrap around one of the remaining bounding constraints
525 * and continue the process until all bounding constraints have been
526 * taken into account.
527 * The resulting linear combination of the bounding constraints will
528 * correspond to a facet of the convex hull.
530 static struct isl_mat *initial_facet_constraint(struct isl_set *set,
531 struct isl_mat *bounds)
533 struct isl_set *slice = NULL;
534 struct isl_basic_set *face = NULL;
535 struct isl_mat *m, *U, *Q;
537 unsigned dim = isl_set_n_dim(set);
539 isl_assert(set->ctx, set->n > 0, goto error);
540 isl_assert(set->ctx, bounds->n_row == dim, goto error);
542 while (bounds->n_row > 1) {
543 slice = isl_set_copy(set);
544 slice = isl_set_add_equality(slice, bounds->row[0]);
545 face = isl_set_affine_hull(slice);
548 if (face->n_eq == 1) {
549 isl_basic_set_free(face);
552 m = isl_mat_alloc(set->ctx, 1 + face->n_eq, 1 + dim);
555 isl_int_set_si(m->row[0][0], 1);
556 isl_seq_clr(m->row[0]+1, dim);
557 for (i = 0; i < face->n_eq; ++i)
558 isl_seq_cpy(m->row[1 + i], face->eq[i], 1 + dim);
559 U = isl_mat_right_inverse(m);
560 Q = isl_mat_right_inverse(isl_mat_copy(U));
561 U = isl_mat_drop_cols(U, 1 + face->n_eq, dim - face->n_eq);
562 Q = isl_mat_drop_rows(Q, 1 + face->n_eq, dim - face->n_eq);
563 U = isl_mat_drop_cols(U, 0, 1);
564 Q = isl_mat_drop_rows(Q, 0, 1);
565 bounds = isl_mat_product(bounds, U);
566 bounds = isl_mat_product(bounds, Q);
567 while (isl_seq_first_non_zero(bounds->row[bounds->n_row-1],
568 bounds->n_col) == -1) {
570 isl_assert(set->ctx, bounds->n_row > 1, goto error);
572 if (!wrap_facet(set, bounds->row[0],
573 bounds->row[bounds->n_row-1]))
575 isl_basic_set_free(face);
580 isl_basic_set_free(face);
581 isl_mat_free(bounds);
585 /* Given the bounding constraint "c" of a facet of the convex hull of "set",
586 * compute a hyperplane description of the facet, i.e., compute the facets
589 * We compute an affine transformation that transforms the constraint
598 * by computing the right inverse U of a matrix that starts with the rows
611 * Since z_1 is zero, we can drop this variable as well as the corresponding
612 * column of U to obtain
620 * with Q' equal to Q, but without the corresponding row.
621 * After computing the facets of the facet in the z' space,
622 * we convert them back to the x space through Q.
624 static struct isl_basic_set *compute_facet(struct isl_set *set, isl_int *c)
626 struct isl_mat *m, *U, *Q;
627 struct isl_basic_set *facet = NULL;
632 set = isl_set_copy(set);
633 dim = isl_set_n_dim(set);
634 m = isl_mat_alloc(set->ctx, 2, 1 + dim);
637 isl_int_set_si(m->row[0][0], 1);
638 isl_seq_clr(m->row[0]+1, dim);
639 isl_seq_cpy(m->row[1], c, 1+dim);
640 U = isl_mat_right_inverse(m);
641 Q = isl_mat_right_inverse(isl_mat_copy(U));
642 U = isl_mat_drop_cols(U, 1, 1);
643 Q = isl_mat_drop_rows(Q, 1, 1);
644 set = isl_set_preimage(set, U);
645 facet = uset_convex_hull_wrap_bounded(set);
646 facet = isl_basic_set_preimage(facet, Q);
647 isl_assert(ctx, facet->n_eq == 0, goto error);
650 isl_basic_set_free(facet);
655 /* Given an initial facet constraint, compute the remaining facets.
656 * We do this by running through all facets found so far and computing
657 * the adjacent facets through wrapping, adding those facets that we
658 * hadn't already found before.
660 * For each facet we have found so far, we first compute its facets
661 * in the resulting convex hull. That is, we compute the ridges
662 * of the resulting convex hull contained in the facet.
663 * We also compute the corresponding facet in the current approximation
664 * of the convex hull. There is no need to wrap around the ridges
665 * in this facet since that would result in a facet that is already
666 * present in the current approximation.
668 * This function can still be significantly optimized by checking which of
669 * the facets of the basic sets are also facets of the convex hull and
670 * using all the facets so far to help in constructing the facets of the
673 * using the technique in section "3.1 Ridge Generation" of
674 * "Extended Convex Hull" by Fukuda et al.
676 static struct isl_basic_set *extend(struct isl_basic_set *hull,
681 struct isl_basic_set *facet = NULL;
682 struct isl_basic_set *hull_facet = NULL;
688 isl_assert(set->ctx, set->n > 0, goto error);
690 dim = isl_set_n_dim(set);
692 for (i = 0; i < hull->n_ineq; ++i) {
693 facet = compute_facet(set, hull->ineq[i]);
694 facet = isl_basic_set_add_equality(facet, hull->ineq[i]);
695 facet = isl_basic_set_gauss(facet, NULL);
696 facet = isl_basic_set_normalize_constraints(facet);
697 hull_facet = isl_basic_set_copy(hull);
698 hull_facet = isl_basic_set_add_equality(hull_facet, hull->ineq[i]);
699 hull_facet = isl_basic_set_gauss(hull_facet, NULL);
700 hull_facet = isl_basic_set_normalize_constraints(hull_facet);
703 hull = isl_basic_set_cow(hull);
704 hull = isl_basic_set_extend_dim(hull,
705 isl_dim_copy(hull->dim), 0, 0, facet->n_ineq);
706 for (j = 0; j < facet->n_ineq; ++j) {
707 for (f = 0; f < hull_facet->n_ineq; ++f)
708 if (isl_seq_eq(facet->ineq[j],
709 hull_facet->ineq[f], 1 + dim))
711 if (f < hull_facet->n_ineq)
713 k = isl_basic_set_alloc_inequality(hull);
716 isl_seq_cpy(hull->ineq[k], hull->ineq[i], 1+dim);
717 if (!wrap_facet(set, hull->ineq[k], facet->ineq[j]))
720 isl_basic_set_free(hull_facet);
721 isl_basic_set_free(facet);
723 hull = isl_basic_set_simplify(hull);
724 hull = isl_basic_set_finalize(hull);
727 isl_basic_set_free(hull_facet);
728 isl_basic_set_free(facet);
729 isl_basic_set_free(hull);
733 /* Special case for computing the convex hull of a one dimensional set.
734 * We simply collect the lower and upper bounds of each basic set
735 * and the biggest of those.
737 static struct isl_basic_set *convex_hull_1d(struct isl_set *set)
739 struct isl_mat *c = NULL;
740 isl_int *lower = NULL;
741 isl_int *upper = NULL;
744 struct isl_basic_set *hull;
746 for (i = 0; i < set->n; ++i) {
747 set->p[i] = isl_basic_set_simplify(set->p[i]);
751 set = isl_set_remove_empty_parts(set);
754 isl_assert(set->ctx, set->n > 0, goto error);
755 c = isl_mat_alloc(set->ctx, 2, 2);
759 if (set->p[0]->n_eq > 0) {
760 isl_assert(set->ctx, set->p[0]->n_eq == 1, goto error);
763 if (isl_int_is_pos(set->p[0]->eq[0][1])) {
764 isl_seq_cpy(lower, set->p[0]->eq[0], 2);
765 isl_seq_neg(upper, set->p[0]->eq[0], 2);
767 isl_seq_neg(lower, set->p[0]->eq[0], 2);
768 isl_seq_cpy(upper, set->p[0]->eq[0], 2);
771 for (j = 0; j < set->p[0]->n_ineq; ++j) {
772 if (isl_int_is_pos(set->p[0]->ineq[j][1])) {
774 isl_seq_cpy(lower, set->p[0]->ineq[j], 2);
777 isl_seq_cpy(upper, set->p[0]->ineq[j], 2);
784 for (i = 0; i < set->n; ++i) {
785 struct isl_basic_set *bset = set->p[i];
789 for (j = 0; j < bset->n_eq; ++j) {
793 isl_int_mul(a, lower[0], bset->eq[j][1]);
794 isl_int_mul(b, lower[1], bset->eq[j][0]);
795 if (isl_int_lt(a, b) && isl_int_is_pos(bset->eq[j][1]))
796 isl_seq_cpy(lower, bset->eq[j], 2);
797 if (isl_int_gt(a, b) && isl_int_is_neg(bset->eq[j][1]))
798 isl_seq_neg(lower, bset->eq[j], 2);
801 isl_int_mul(a, upper[0], bset->eq[j][1]);
802 isl_int_mul(b, upper[1], bset->eq[j][0]);
803 if (isl_int_lt(a, b) && isl_int_is_pos(bset->eq[j][1]))
804 isl_seq_neg(upper, bset->eq[j], 2);
805 if (isl_int_gt(a, b) && isl_int_is_neg(bset->eq[j][1]))
806 isl_seq_cpy(upper, bset->eq[j], 2);
809 for (j = 0; j < bset->n_ineq; ++j) {
810 if (isl_int_is_pos(bset->ineq[j][1]))
812 if (isl_int_is_neg(bset->ineq[j][1]))
814 if (lower && isl_int_is_pos(bset->ineq[j][1])) {
815 isl_int_mul(a, lower[0], bset->ineq[j][1]);
816 isl_int_mul(b, lower[1], bset->ineq[j][0]);
817 if (isl_int_lt(a, b))
818 isl_seq_cpy(lower, bset->ineq[j], 2);
820 if (upper && isl_int_is_neg(bset->ineq[j][1])) {
821 isl_int_mul(a, upper[0], bset->ineq[j][1]);
822 isl_int_mul(b, upper[1], bset->ineq[j][0]);
823 if (isl_int_gt(a, b))
824 isl_seq_cpy(upper, bset->ineq[j], 2);
835 hull = isl_basic_set_alloc(set->ctx, 0, 1, 0, 0, 2);
836 hull = isl_basic_set_set_rational(hull);
840 k = isl_basic_set_alloc_inequality(hull);
841 isl_seq_cpy(hull->ineq[k], lower, 2);
844 k = isl_basic_set_alloc_inequality(hull);
845 isl_seq_cpy(hull->ineq[k], upper, 2);
847 hull = isl_basic_set_finalize(hull);
857 /* Project out final n dimensions using Fourier-Motzkin */
858 static struct isl_set *set_project_out(struct isl_ctx *ctx,
859 struct isl_set *set, unsigned n)
861 return isl_set_remove_dims(set, isl_set_n_dim(set) - n, n);
864 static struct isl_basic_set *convex_hull_0d(struct isl_set *set)
866 struct isl_basic_set *convex_hull;
871 if (isl_set_is_empty(set))
872 convex_hull = isl_basic_set_empty(isl_dim_copy(set->dim));
874 convex_hull = isl_basic_set_universe(isl_dim_copy(set->dim));
879 /* Compute the convex hull of a pair of basic sets without any parameters or
880 * integer divisions using Fourier-Motzkin elimination.
881 * The convex hull is the set of all points that can be written as
882 * the sum of points from both basic sets (in homogeneous coordinates).
883 * We set up the constraints in a space with dimensions for each of
884 * the three sets and then project out the dimensions corresponding
885 * to the two original basic sets, retaining only those corresponding
886 * to the convex hull.
888 static struct isl_basic_set *convex_hull_pair_elim(struct isl_basic_set *bset1,
889 struct isl_basic_set *bset2)
892 struct isl_basic_set *bset[2];
893 struct isl_basic_set *hull = NULL;
896 if (!bset1 || !bset2)
899 dim = isl_basic_set_n_dim(bset1);
900 hull = isl_basic_set_alloc(bset1->ctx, 0, 2 + 3 * dim, 0,
901 1 + dim + bset1->n_eq + bset2->n_eq,
902 2 + bset1->n_ineq + bset2->n_ineq);
905 for (i = 0; i < 2; ++i) {
906 for (j = 0; j < bset[i]->n_eq; ++j) {
907 k = isl_basic_set_alloc_equality(hull);
910 isl_seq_clr(hull->eq[k], (i+1) * (1+dim));
911 isl_seq_clr(hull->eq[k]+(i+2)*(1+dim), (1-i)*(1+dim));
912 isl_seq_cpy(hull->eq[k]+(i+1)*(1+dim), bset[i]->eq[j],
915 for (j = 0; j < bset[i]->n_ineq; ++j) {
916 k = isl_basic_set_alloc_inequality(hull);
919 isl_seq_clr(hull->ineq[k], (i+1) * (1+dim));
920 isl_seq_clr(hull->ineq[k]+(i+2)*(1+dim), (1-i)*(1+dim));
921 isl_seq_cpy(hull->ineq[k]+(i+1)*(1+dim),
922 bset[i]->ineq[j], 1+dim);
924 k = isl_basic_set_alloc_inequality(hull);
927 isl_seq_clr(hull->ineq[k], 1+2+3*dim);
928 isl_int_set_si(hull->ineq[k][(i+1)*(1+dim)], 1);
930 for (j = 0; j < 1+dim; ++j) {
931 k = isl_basic_set_alloc_equality(hull);
934 isl_seq_clr(hull->eq[k], 1+2+3*dim);
935 isl_int_set_si(hull->eq[k][j], -1);
936 isl_int_set_si(hull->eq[k][1+dim+j], 1);
937 isl_int_set_si(hull->eq[k][2*(1+dim)+j], 1);
939 hull = isl_basic_set_set_rational(hull);
940 hull = isl_basic_set_remove_dims(hull, dim, 2*(1+dim));
941 hull = isl_basic_set_convex_hull(hull);
942 isl_basic_set_free(bset1);
943 isl_basic_set_free(bset2);
946 isl_basic_set_free(bset1);
947 isl_basic_set_free(bset2);
948 isl_basic_set_free(hull);
952 static int isl_basic_set_is_bounded(struct isl_basic_set *bset)
957 tab = isl_tab_from_recession_cone(bset);
958 bounded = isl_tab_cone_is_bounded(tab);
963 static int isl_set_is_bounded(struct isl_set *set)
967 for (i = 0; i < set->n; ++i) {
968 int bounded = isl_basic_set_is_bounded(set->p[i]);
969 if (!bounded || bounded < 0)
975 /* Compute the lineality space of the convex hull of bset1 and bset2.
977 * We first compute the intersection of the recession cone of bset1
978 * with the negative of the recession cone of bset2 and then compute
979 * the linear hull of the resulting cone.
981 static struct isl_basic_set *induced_lineality_space(
982 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
985 struct isl_basic_set *lin = NULL;
988 if (!bset1 || !bset2)
991 dim = isl_basic_set_total_dim(bset1);
992 lin = isl_basic_set_alloc_dim(isl_basic_set_get_dim(bset1), 0,
993 bset1->n_eq + bset2->n_eq,
994 bset1->n_ineq + bset2->n_ineq);
995 lin = isl_basic_set_set_rational(lin);
998 for (i = 0; i < bset1->n_eq; ++i) {
999 k = isl_basic_set_alloc_equality(lin);
1002 isl_int_set_si(lin->eq[k][0], 0);
1003 isl_seq_cpy(lin->eq[k] + 1, bset1->eq[i] + 1, dim);
1005 for (i = 0; i < bset1->n_ineq; ++i) {
1006 k = isl_basic_set_alloc_inequality(lin);
1009 isl_int_set_si(lin->ineq[k][0], 0);
1010 isl_seq_cpy(lin->ineq[k] + 1, bset1->ineq[i] + 1, dim);
1012 for (i = 0; i < bset2->n_eq; ++i) {
1013 k = isl_basic_set_alloc_equality(lin);
1016 isl_int_set_si(lin->eq[k][0], 0);
1017 isl_seq_neg(lin->eq[k] + 1, bset2->eq[i] + 1, dim);
1019 for (i = 0; i < bset2->n_ineq; ++i) {
1020 k = isl_basic_set_alloc_inequality(lin);
1023 isl_int_set_si(lin->ineq[k][0], 0);
1024 isl_seq_neg(lin->ineq[k] + 1, bset2->ineq[i] + 1, dim);
1027 isl_basic_set_free(bset1);
1028 isl_basic_set_free(bset2);
1029 return isl_basic_set_affine_hull(lin);
1031 isl_basic_set_free(lin);
1032 isl_basic_set_free(bset1);
1033 isl_basic_set_free(bset2);
1037 static struct isl_basic_set *uset_convex_hull(struct isl_set *set);
1039 /* Given a set and a linear space "lin" of dimension n > 0,
1040 * project the linear space from the set, compute the convex hull
1041 * and then map the set back to the original space.
1047 * describe the linear space. We first compute the Hermite normal
1048 * form H = M U of M = H Q, to obtain
1052 * The last n rows of H will be zero, so the last n variables of x' = Q x
1053 * are the one we want to project out. We do this by transforming each
1054 * basic set A x >= b to A U x' >= b and then removing the last n dimensions.
1055 * After computing the convex hull in x'_1, i.e., A' x'_1 >= b',
1056 * we transform the hull back to the original space as A' Q_1 x >= b',
1057 * with Q_1 all but the last n rows of Q.
1059 static struct isl_basic_set *modulo_lineality(struct isl_set *set,
1060 struct isl_basic_set *lin)
1062 unsigned total = isl_basic_set_total_dim(lin);
1064 struct isl_basic_set *hull;
1065 struct isl_mat *M, *U, *Q;
1069 lin_dim = total - lin->n_eq;
1070 M = isl_mat_sub_alloc(set->ctx, lin->eq, 0, lin->n_eq, 1, total);
1071 M = isl_mat_left_hermite(M, 0, &U, &Q);
1075 isl_basic_set_free(lin);
1077 Q = isl_mat_drop_rows(Q, Q->n_row - lin_dim, lin_dim);
1079 U = isl_mat_lin_to_aff(U);
1080 Q = isl_mat_lin_to_aff(Q);
1082 set = isl_set_preimage(set, U);
1083 set = isl_set_remove_dims(set, total - lin_dim, lin_dim);
1084 hull = uset_convex_hull(set);
1085 hull = isl_basic_set_preimage(hull, Q);
1089 isl_basic_set_free(lin);
1094 /* Given two polyhedra with as constraints h_{ij} x >= 0 in homegeneous space,
1095 * set up an LP for solving
1097 * \sum_j \alpha_{1j} h_{1j} = \sum_j \alpha_{2j} h_{2j}
1099 * \alpha{i0} corresponds to the (implicit) positivity constraint 1 >= 0
1100 * The next \alpha{ij} correspond to the equalities and come in pairs.
1101 * The final \alpha{ij} correspond to the inequalities.
1103 static struct isl_basic_set *valid_direction_lp(
1104 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1106 struct isl_dim *dim;
1107 struct isl_basic_set *lp;
1112 if (!bset1 || !bset2)
1114 d = 1 + isl_basic_set_total_dim(bset1);
1116 2 * bset1->n_eq + bset1->n_ineq + 2 * bset2->n_eq + bset2->n_ineq;
1117 dim = isl_dim_set_alloc(bset1->ctx, 0, n);
1118 lp = isl_basic_set_alloc_dim(dim, 0, d, n);
1121 for (i = 0; i < n; ++i) {
1122 k = isl_basic_set_alloc_inequality(lp);
1125 isl_seq_clr(lp->ineq[k] + 1, n);
1126 isl_int_set_si(lp->ineq[k][0], -1);
1127 isl_int_set_si(lp->ineq[k][1 + i], 1);
1129 for (i = 0; i < d; ++i) {
1130 k = isl_basic_set_alloc_equality(lp);
1134 isl_int_set_si(lp->eq[k][n++], 0);
1135 /* positivity constraint 1 >= 0 */
1136 isl_int_set_si(lp->eq[k][n++], i == 0);
1137 for (j = 0; j < bset1->n_eq; ++j) {
1138 isl_int_set(lp->eq[k][n++], bset1->eq[j][i]);
1139 isl_int_neg(lp->eq[k][n++], bset1->eq[j][i]);
1141 for (j = 0; j < bset1->n_ineq; ++j)
1142 isl_int_set(lp->eq[k][n++], bset1->ineq[j][i]);
1143 /* positivity constraint 1 >= 0 */
1144 isl_int_set_si(lp->eq[k][n++], -(i == 0));
1145 for (j = 0; j < bset2->n_eq; ++j) {
1146 isl_int_neg(lp->eq[k][n++], bset2->eq[j][i]);
1147 isl_int_set(lp->eq[k][n++], bset2->eq[j][i]);
1149 for (j = 0; j < bset2->n_ineq; ++j)
1150 isl_int_neg(lp->eq[k][n++], bset2->ineq[j][i]);
1152 lp = isl_basic_set_gauss(lp, NULL);
1153 isl_basic_set_free(bset1);
1154 isl_basic_set_free(bset2);
1157 isl_basic_set_free(bset1);
1158 isl_basic_set_free(bset2);
1162 /* Compute a vector s in the homogeneous space such that <s, r> > 0
1163 * for all rays in the homogeneous space of the two cones that correspond
1164 * to the input polyhedra bset1 and bset2.
1166 * We compute s as a vector that satisfies
1168 * s = \sum_j \alpha_{ij} h_{ij} for i = 1,2 (*)
1170 * with h_{ij} the normals of the facets of polyhedron i
1171 * (including the "positivity constraint" 1 >= 0) and \alpha_{ij}
1172 * strictly positive numbers. For simplicity we impose \alpha_{ij} >= 1.
1173 * We first set up an LP with as variables the \alpha{ij}.
1174 * In this formulateion, for each polyhedron i,
1175 * the first constraint is the positivity constraint, followed by pairs
1176 * of variables for the equalities, followed by variables for the inequalities.
1177 * We then simply pick a feasible solution and compute s using (*).
1179 * Note that we simply pick any valid direction and make no attempt
1180 * to pick a "good" or even the "best" valid direction.
1182 static struct isl_vec *valid_direction(
1183 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1185 struct isl_basic_set *lp;
1186 struct isl_tab *tab;
1187 struct isl_vec *sample = NULL;
1188 struct isl_vec *dir;
1193 if (!bset1 || !bset2)
1195 lp = valid_direction_lp(isl_basic_set_copy(bset1),
1196 isl_basic_set_copy(bset2));
1197 tab = isl_tab_from_basic_set(lp);
1198 sample = isl_tab_get_sample_value(tab);
1200 isl_basic_set_free(lp);
1203 d = isl_basic_set_total_dim(bset1);
1204 dir = isl_vec_alloc(bset1->ctx, 1 + d);
1207 isl_seq_clr(dir->block.data + 1, dir->size - 1);
1209 /* positivity constraint 1 >= 0 */
1210 isl_int_set(dir->block.data[0], sample->block.data[n++]);
1211 for (i = 0; i < bset1->n_eq; ++i) {
1212 isl_int_sub(sample->block.data[n],
1213 sample->block.data[n], sample->block.data[n+1]);
1214 isl_seq_combine(dir->block.data,
1215 bset1->ctx->one, dir->block.data,
1216 sample->block.data[n], bset1->eq[i], 1 + d);
1220 for (i = 0; i < bset1->n_ineq; ++i)
1221 isl_seq_combine(dir->block.data,
1222 bset1->ctx->one, dir->block.data,
1223 sample->block.data[n++], bset1->ineq[i], 1 + d);
1224 isl_vec_free(sample);
1225 isl_seq_normalize(bset1->ctx, dir->block.data + 1, dir->size - 1);
1226 isl_basic_set_free(bset1);
1227 isl_basic_set_free(bset2);
1230 isl_vec_free(sample);
1231 isl_basic_set_free(bset1);
1232 isl_basic_set_free(bset2);
1236 /* Given a polyhedron b_i + A_i x >= 0 and a map T = S^{-1},
1237 * compute b_i' + A_i' x' >= 0, with
1239 * [ b_i A_i ] [ y' ] [ y' ]
1240 * [ 1 0 ] S^{-1} [ x' ] >= 0 or [ b_i' A_i' ] [ x' ] >= 0
1242 * In particular, add the "positivity constraint" and then perform
1245 static struct isl_basic_set *homogeneous_map(struct isl_basic_set *bset,
1252 bset = isl_basic_set_extend_constraints(bset, 0, 1);
1253 k = isl_basic_set_alloc_inequality(bset);
1256 isl_seq_clr(bset->ineq[k] + 1, isl_basic_set_total_dim(bset));
1257 isl_int_set_si(bset->ineq[k][0], 1);
1258 bset = isl_basic_set_preimage(bset, T);
1262 isl_basic_set_free(bset);
1266 /* Compute the convex hull of a pair of basic sets without any parameters or
1267 * integer divisions, where the convex hull is known to be pointed,
1268 * but the basic sets may be unbounded.
1270 * We turn this problem into the computation of a convex hull of a pair
1271 * _bounded_ polyhedra by "changing the direction of the homogeneous
1272 * dimension". This idea is due to Matthias Koeppe.
1274 * Consider the cones in homogeneous space that correspond to the
1275 * input polyhedra. The rays of these cones are also rays of the
1276 * polyhedra if the coordinate that corresponds to the homogeneous
1277 * dimension is zero. That is, if the inner product of the rays
1278 * with the homogeneous direction is zero.
1279 * The cones in the homogeneous space can also be considered to
1280 * correspond to other pairs of polyhedra by chosing a different
1281 * homogeneous direction. To ensure that both of these polyhedra
1282 * are bounded, we need to make sure that all rays of the cones
1283 * correspond to vertices and not to rays.
1284 * Let s be a direction such that <s, r> > 0 for all rays r of both cones.
1285 * Then using s as a homogeneous direction, we obtain a pair of polytopes.
1286 * The vector s is computed in valid_direction.
1288 * Note that we need to consider _all_ rays of the cones and not just
1289 * the rays that correspond to rays in the polyhedra. If we were to
1290 * only consider those rays and turn them into vertices, then we
1291 * may inadvertently turn some vertices into rays.
1293 * The standard homogeneous direction is the unit vector in the 0th coordinate.
1294 * We therefore transform the two polyhedra such that the selected
1295 * direction is mapped onto this standard direction and then proceed
1296 * with the normal computation.
1297 * Let S be a non-singular square matrix with s as its first row,
1298 * then we want to map the polyhedra to the space
1300 * [ y' ] [ y ] [ y ] [ y' ]
1301 * [ x' ] = S [ x ] i.e., [ x ] = S^{-1} [ x' ]
1303 * We take S to be the unimodular completion of s to limit the growth
1304 * of the coefficients in the following computations.
1306 * Let b_i + A_i x >= 0 be the constraints of polyhedron i.
1307 * We first move to the homogeneous dimension
1309 * b_i y + A_i x >= 0 [ b_i A_i ] [ y ] [ 0 ]
1310 * y >= 0 or [ 1 0 ] [ x ] >= [ 0 ]
1312 * Then we change directoin
1314 * [ b_i A_i ] [ y' ] [ y' ]
1315 * [ 1 0 ] S^{-1} [ x' ] >= 0 or [ b_i' A_i' ] [ x' ] >= 0
1317 * Then we compute the convex hull of the polytopes b_i' + A_i' x' >= 0
1318 * resulting in b' + A' x' >= 0, which we then convert back
1321 * [ b' A' ] S [ x ] >= 0 or [ b A ] [ x ] >= 0
1323 * The polyhedron b + A x >= 0 is then the convex hull of the input polyhedra.
1325 static struct isl_basic_set *convex_hull_pair_pointed(
1326 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1328 struct isl_ctx *ctx = NULL;
1329 struct isl_vec *dir = NULL;
1330 struct isl_mat *T = NULL;
1331 struct isl_mat *T2 = NULL;
1332 struct isl_basic_set *hull;
1333 struct isl_set *set;
1335 if (!bset1 || !bset2)
1338 dir = valid_direction(isl_basic_set_copy(bset1),
1339 isl_basic_set_copy(bset2));
1342 T = isl_mat_alloc(bset1->ctx, dir->size, dir->size);
1345 isl_seq_cpy(T->row[0], dir->block.data, dir->size);
1346 T = isl_mat_unimodular_complete(T, 1);
1347 T2 = isl_mat_right_inverse(isl_mat_copy(T));
1349 bset1 = homogeneous_map(bset1, isl_mat_copy(T2));
1350 bset2 = homogeneous_map(bset2, T2);
1351 set = isl_set_alloc_dim(isl_basic_set_get_dim(bset1), 2, 0);
1352 set = isl_set_add(set, bset1);
1353 set = isl_set_add(set, bset2);
1354 hull = uset_convex_hull(set);
1355 hull = isl_basic_set_preimage(hull, T);
1362 isl_basic_set_free(bset1);
1363 isl_basic_set_free(bset2);
1367 /* Compute the convex hull of a pair of basic sets without any parameters or
1368 * integer divisions.
1370 * If the convex hull of the two basic sets would have a non-trivial
1371 * lineality space, we first project out this lineality space.
1373 static struct isl_basic_set *convex_hull_pair(struct isl_basic_set *bset1,
1374 struct isl_basic_set *bset2)
1376 struct isl_basic_set *lin;
1378 if (isl_basic_set_is_bounded(bset1) || isl_basic_set_is_bounded(bset2))
1379 return convex_hull_pair_pointed(bset1, bset2);
1381 lin = induced_lineality_space(isl_basic_set_copy(bset1),
1382 isl_basic_set_copy(bset2));
1385 if (isl_basic_set_is_universe(lin)) {
1386 isl_basic_set_free(bset1);
1387 isl_basic_set_free(bset2);
1390 if (lin->n_eq < isl_basic_set_total_dim(lin)) {
1391 struct isl_set *set;
1392 set = isl_set_alloc_dim(isl_basic_set_get_dim(bset1), 2, 0);
1393 set = isl_set_add(set, bset1);
1394 set = isl_set_add(set, bset2);
1395 return modulo_lineality(set, lin);
1397 isl_basic_set_free(lin);
1399 return convex_hull_pair_pointed(bset1, bset2);
1401 isl_basic_set_free(bset1);
1402 isl_basic_set_free(bset2);
1406 /* Compute the lineality space of a basic set.
1407 * We currently do not allow the basic set to have any divs.
1408 * We basically just drop the constants and turn every inequality
1411 struct isl_basic_set *isl_basic_set_lineality_space(struct isl_basic_set *bset)
1414 struct isl_basic_set *lin = NULL;
1419 isl_assert(bset->ctx, bset->n_div == 0, goto error);
1420 dim = isl_basic_set_total_dim(bset);
1422 lin = isl_basic_set_alloc_dim(isl_basic_set_get_dim(bset), 0, dim, 0);
1425 for (i = 0; i < bset->n_eq; ++i) {
1426 k = isl_basic_set_alloc_equality(lin);
1429 isl_int_set_si(lin->eq[k][0], 0);
1430 isl_seq_cpy(lin->eq[k] + 1, bset->eq[i] + 1, dim);
1432 lin = isl_basic_set_gauss(lin, NULL);
1435 for (i = 0; i < bset->n_ineq && lin->n_eq < dim; ++i) {
1436 k = isl_basic_set_alloc_equality(lin);
1439 isl_int_set_si(lin->eq[k][0], 0);
1440 isl_seq_cpy(lin->eq[k] + 1, bset->ineq[i] + 1, dim);
1441 lin = isl_basic_set_gauss(lin, NULL);
1445 isl_basic_set_free(bset);
1448 isl_basic_set_free(lin);
1449 isl_basic_set_free(bset);
1453 /* Compute the (linear) hull of the lineality spaces of the basic sets in the
1454 * "underlying" set "set".
1456 static struct isl_basic_set *uset_combined_lineality_space(struct isl_set *set)
1459 struct isl_set *lin = NULL;
1464 struct isl_dim *dim = isl_set_get_dim(set);
1466 return isl_basic_set_empty(dim);
1469 lin = isl_set_alloc_dim(isl_set_get_dim(set), set->n, 0);
1470 for (i = 0; i < set->n; ++i)
1471 lin = isl_set_add(lin,
1472 isl_basic_set_lineality_space(isl_basic_set_copy(set->p[i])));
1474 return isl_set_affine_hull(lin);
1477 /* Compute the convex hull of a set without any parameters or
1478 * integer divisions.
1479 * In each step, we combined two basic sets until only one
1480 * basic set is left.
1481 * The input basic sets are assumed not to have a non-trivial
1482 * lineality space. If any of the intermediate results has
1483 * a non-trivial lineality space, it is projected out.
1485 static struct isl_basic_set *uset_convex_hull_unbounded(struct isl_set *set)
1487 struct isl_basic_set *convex_hull = NULL;
1489 convex_hull = isl_set_copy_basic_set(set);
1490 set = isl_set_drop_basic_set(set, convex_hull);
1493 while (set->n > 0) {
1494 struct isl_basic_set *t;
1495 t = isl_set_copy_basic_set(set);
1498 set = isl_set_drop_basic_set(set, t);
1501 convex_hull = convex_hull_pair(convex_hull, t);
1504 t = isl_basic_set_lineality_space(isl_basic_set_copy(convex_hull));
1507 if (isl_basic_set_is_universe(t)) {
1508 isl_basic_set_free(convex_hull);
1512 if (t->n_eq < isl_basic_set_total_dim(t)) {
1513 set = isl_set_add(set, convex_hull);
1514 return modulo_lineality(set, t);
1516 isl_basic_set_free(t);
1522 isl_basic_set_free(convex_hull);
1526 /* Compute an initial hull for wrapping containing a single initial
1527 * facet by first computing bounds on the set and then using these
1528 * bounds to construct an initial facet.
1529 * This function is a remnant of an older implementation where the
1530 * bounds were also used to check whether the set was bounded.
1531 * Since this function will now only be called when we know the
1532 * set to be bounded, the initial facet should probably be constructed
1533 * by simply using the coordinate directions instead.
1535 static struct isl_basic_set *initial_hull(struct isl_basic_set *hull,
1536 struct isl_set *set)
1538 struct isl_mat *bounds = NULL;
1544 bounds = independent_bounds(set);
1547 isl_assert(set->ctx, bounds->n_row == isl_set_n_dim(set), goto error);
1548 bounds = initial_facet_constraint(set, bounds);
1551 k = isl_basic_set_alloc_inequality(hull);
1554 dim = isl_set_n_dim(set);
1555 isl_assert(set->ctx, 1 + dim == bounds->n_col, goto error);
1556 isl_seq_cpy(hull->ineq[k], bounds->row[0], bounds->n_col);
1557 isl_mat_free(bounds);
1561 isl_basic_set_free(hull);
1562 isl_mat_free(bounds);
1566 struct max_constraint {
1572 static int max_constraint_equal(const void *entry, const void *val)
1574 struct max_constraint *a = (struct max_constraint *)entry;
1575 isl_int *b = (isl_int *)val;
1577 return isl_seq_eq(a->c->row[0] + 1, b, a->c->n_col - 1);
1580 static void update_constraint(struct isl_ctx *ctx, struct isl_hash_table *table,
1581 isl_int *con, unsigned len, int n, int ineq)
1583 struct isl_hash_table_entry *entry;
1584 struct max_constraint *c;
1587 c_hash = isl_seq_get_hash(con + 1, len);
1588 entry = isl_hash_table_find(ctx, table, c_hash, max_constraint_equal,
1594 isl_hash_table_remove(ctx, table, entry);
1598 if (isl_int_gt(c->c->row[0][0], con[0]))
1600 if (isl_int_eq(c->c->row[0][0], con[0])) {
1605 c->c = isl_mat_cow(c->c);
1606 isl_int_set(c->c->row[0][0], con[0]);
1610 /* Check whether the constraint hash table "table" constains the constraint
1613 static int has_constraint(struct isl_ctx *ctx, struct isl_hash_table *table,
1614 isl_int *con, unsigned len, int n)
1616 struct isl_hash_table_entry *entry;
1617 struct max_constraint *c;
1620 c_hash = isl_seq_get_hash(con + 1, len);
1621 entry = isl_hash_table_find(ctx, table, c_hash, max_constraint_equal,
1628 return isl_int_eq(c->c->row[0][0], con[0]);
1631 /* Check for inequality constraints of a basic set without equalities
1632 * such that the same or more stringent copies of the constraint appear
1633 * in all of the basic sets. Such constraints are necessarily facet
1634 * constraints of the convex hull.
1636 * If the resulting basic set is by chance identical to one of
1637 * the basic sets in "set", then we know that this basic set contains
1638 * all other basic sets and is therefore the convex hull of set.
1639 * In this case we set *is_hull to 1.
1641 static struct isl_basic_set *common_constraints(struct isl_basic_set *hull,
1642 struct isl_set *set, int *is_hull)
1645 int min_constraints;
1647 struct max_constraint *constraints = NULL;
1648 struct isl_hash_table *table = NULL;
1653 for (i = 0; i < set->n; ++i)
1654 if (set->p[i]->n_eq == 0)
1658 min_constraints = set->p[i]->n_ineq;
1660 for (i = best + 1; i < set->n; ++i) {
1661 if (set->p[i]->n_eq != 0)
1663 if (set->p[i]->n_ineq >= min_constraints)
1665 min_constraints = set->p[i]->n_ineq;
1668 constraints = isl_calloc_array(hull->ctx, struct max_constraint,
1672 table = isl_alloc_type(hull->ctx, struct isl_hash_table);
1673 if (isl_hash_table_init(hull->ctx, table, min_constraints))
1676 total = isl_dim_total(set->dim);
1677 for (i = 0; i < set->p[best]->n_ineq; ++i) {
1678 constraints[i].c = isl_mat_sub_alloc(hull->ctx,
1679 set->p[best]->ineq + i, 0, 1, 0, 1 + total);
1680 if (!constraints[i].c)
1682 constraints[i].ineq = 1;
1684 for (i = 0; i < min_constraints; ++i) {
1685 struct isl_hash_table_entry *entry;
1687 c_hash = isl_seq_get_hash(constraints[i].c->row[0] + 1, total);
1688 entry = isl_hash_table_find(hull->ctx, table, c_hash,
1689 max_constraint_equal, constraints[i].c->row[0] + 1, 1);
1692 isl_assert(hull->ctx, !entry->data, goto error);
1693 entry->data = &constraints[i];
1697 for (s = 0; s < set->n; ++s) {
1701 for (i = 0; i < set->p[s]->n_eq; ++i) {
1702 isl_int *eq = set->p[s]->eq[i];
1703 for (j = 0; j < 2; ++j) {
1704 isl_seq_neg(eq, eq, 1 + total);
1705 update_constraint(hull->ctx, table,
1709 for (i = 0; i < set->p[s]->n_ineq; ++i) {
1710 isl_int *ineq = set->p[s]->ineq[i];
1711 update_constraint(hull->ctx, table, ineq, total, n,
1712 set->p[s]->n_eq == 0);
1717 for (i = 0; i < min_constraints; ++i) {
1718 if (constraints[i].count < n)
1720 if (!constraints[i].ineq)
1722 j = isl_basic_set_alloc_inequality(hull);
1725 isl_seq_cpy(hull->ineq[j], constraints[i].c->row[0], 1 + total);
1728 for (s = 0; s < set->n; ++s) {
1729 if (set->p[s]->n_eq)
1731 if (set->p[s]->n_ineq != hull->n_ineq)
1733 for (i = 0; i < set->p[s]->n_ineq; ++i) {
1734 isl_int *ineq = set->p[s]->ineq[i];
1735 if (!has_constraint(hull->ctx, table, ineq, total, n))
1738 if (i == set->p[s]->n_ineq)
1742 isl_hash_table_clear(table);
1743 for (i = 0; i < min_constraints; ++i)
1744 isl_mat_free(constraints[i].c);
1749 isl_hash_table_clear(table);
1752 for (i = 0; i < min_constraints; ++i)
1753 isl_mat_free(constraints[i].c);
1758 /* Create a template for the convex hull of "set" and fill it up
1759 * obvious facet constraints, if any. If the result happens to
1760 * be the convex hull of "set" then *is_hull is set to 1.
1762 static struct isl_basic_set *proto_hull(struct isl_set *set, int *is_hull)
1764 struct isl_basic_set *hull;
1769 for (i = 0; i < set->n; ++i) {
1770 n_ineq += set->p[i]->n_eq;
1771 n_ineq += set->p[i]->n_ineq;
1773 hull = isl_basic_set_alloc_dim(isl_dim_copy(set->dim), 0, 0, n_ineq);
1774 hull = isl_basic_set_set_rational(hull);
1777 return common_constraints(hull, set, is_hull);
1780 static struct isl_basic_set *uset_convex_hull_wrap(struct isl_set *set)
1782 struct isl_basic_set *hull;
1785 hull = proto_hull(set, &is_hull);
1786 if (hull && !is_hull) {
1787 if (hull->n_ineq == 0)
1788 hull = initial_hull(hull, set);
1789 hull = extend(hull, set);
1796 /* Compute the convex hull of a set without any parameters or
1797 * integer divisions. Depending on whether the set is bounded,
1798 * we pass control to the wrapping based convex hull or
1799 * the Fourier-Motzkin elimination based convex hull.
1800 * We also handle a few special cases before checking the boundedness.
1802 static struct isl_basic_set *uset_convex_hull(struct isl_set *set)
1804 struct isl_basic_set *convex_hull = NULL;
1805 struct isl_basic_set *lin;
1807 if (isl_set_n_dim(set) == 0)
1808 return convex_hull_0d(set);
1810 set = isl_set_coalesce(set);
1811 set = isl_set_set_rational(set);
1818 convex_hull = isl_basic_set_copy(set->p[0]);
1822 if (isl_set_n_dim(set) == 1)
1823 return convex_hull_1d(set);
1825 if (isl_set_is_bounded(set))
1826 return uset_convex_hull_wrap(set);
1828 lin = uset_combined_lineality_space(isl_set_copy(set));
1831 if (isl_basic_set_is_universe(lin)) {
1835 if (lin->n_eq < isl_basic_set_total_dim(lin))
1836 return modulo_lineality(set, lin);
1837 isl_basic_set_free(lin);
1839 return uset_convex_hull_unbounded(set);
1842 isl_basic_set_free(convex_hull);
1846 /* This is the core procedure, where "set" is a "pure" set, i.e.,
1847 * without parameters or divs and where the convex hull of set is
1848 * known to be full-dimensional.
1850 static struct isl_basic_set *uset_convex_hull_wrap_bounded(struct isl_set *set)
1852 struct isl_basic_set *convex_hull = NULL;
1854 if (isl_set_n_dim(set) == 0) {
1855 convex_hull = isl_basic_set_universe(isl_dim_copy(set->dim));
1857 convex_hull = isl_basic_set_set_rational(convex_hull);
1861 set = isl_set_set_rational(set);
1865 set = isl_set_coalesce(set);
1869 convex_hull = isl_basic_set_copy(set->p[0]);
1873 if (isl_set_n_dim(set) == 1)
1874 return convex_hull_1d(set);
1876 return uset_convex_hull_wrap(set);
1882 /* Compute the convex hull of set "set" with affine hull "affine_hull",
1883 * We first remove the equalities (transforming the set), compute the
1884 * convex hull of the transformed set and then add the equalities back
1885 * (after performing the inverse transformation.
1887 static struct isl_basic_set *modulo_affine_hull(struct isl_ctx *ctx,
1888 struct isl_set *set, struct isl_basic_set *affine_hull)
1892 struct isl_basic_set *dummy;
1893 struct isl_basic_set *convex_hull;
1895 dummy = isl_basic_set_remove_equalities(
1896 isl_basic_set_copy(affine_hull), &T, &T2);
1899 isl_basic_set_free(dummy);
1900 set = isl_set_preimage(set, T);
1901 convex_hull = uset_convex_hull(set);
1902 convex_hull = isl_basic_set_preimage(convex_hull, T2);
1903 convex_hull = isl_basic_set_intersect(convex_hull, affine_hull);
1906 isl_basic_set_free(affine_hull);
1911 /* Compute the convex hull of a map.
1913 * The implementation was inspired by "Extended Convex Hull" by Fukuda et al.,
1914 * specifically, the wrapping of facets to obtain new facets.
1916 struct isl_basic_map *isl_map_convex_hull(struct isl_map *map)
1918 struct isl_basic_set *bset;
1919 struct isl_basic_map *model = NULL;
1920 struct isl_basic_set *affine_hull = NULL;
1921 struct isl_basic_map *convex_hull = NULL;
1922 struct isl_set *set = NULL;
1923 struct isl_ctx *ctx;
1930 convex_hull = isl_basic_map_empty_like_map(map);
1935 map = isl_map_detect_equalities(map);
1936 map = isl_map_align_divs(map);
1937 model = isl_basic_map_copy(map->p[0]);
1938 set = isl_map_underlying_set(map);
1942 affine_hull = isl_set_affine_hull(isl_set_copy(set));
1945 if (affine_hull->n_eq != 0)
1946 bset = modulo_affine_hull(ctx, set, affine_hull);
1948 isl_basic_set_free(affine_hull);
1949 bset = uset_convex_hull(set);
1952 convex_hull = isl_basic_map_overlying_set(bset, model);
1954 ISL_F_SET(convex_hull, ISL_BASIC_MAP_NO_IMPLICIT);
1955 ISL_F_SET(convex_hull, ISL_BASIC_MAP_ALL_EQUALITIES);
1956 ISL_F_CLR(convex_hull, ISL_BASIC_MAP_RATIONAL);
1960 isl_basic_map_free(model);
1964 struct isl_basic_set *isl_set_convex_hull(struct isl_set *set)
1966 return (struct isl_basic_set *)
1967 isl_map_convex_hull((struct isl_map *)set);
1970 struct sh_data_entry {
1971 struct isl_hash_table *table;
1972 struct isl_tab *tab;
1975 /* Holds the data needed during the simple hull computation.
1977 * n the number of basic sets in the original set
1978 * hull_table a hash table of already computed constraints
1979 * in the simple hull
1980 * p for each basic set,
1981 * table a hash table of the constraints
1982 * tab the tableau corresponding to the basic set
1985 struct isl_ctx *ctx;
1987 struct isl_hash_table *hull_table;
1988 struct sh_data_entry p[1];
1991 static void sh_data_free(struct sh_data *data)
1997 isl_hash_table_free(data->ctx, data->hull_table);
1998 for (i = 0; i < data->n; ++i) {
1999 isl_hash_table_free(data->ctx, data->p[i].table);
2000 isl_tab_free(data->p[i].tab);
2005 struct ineq_cmp_data {
2010 static int has_ineq(const void *entry, const void *val)
2012 isl_int *row = (isl_int *)entry;
2013 struct ineq_cmp_data *v = (struct ineq_cmp_data *)val;
2015 return isl_seq_eq(row + 1, v->p + 1, v->len) ||
2016 isl_seq_is_neg(row + 1, v->p + 1, v->len);
2019 static int hash_ineq(struct isl_ctx *ctx, struct isl_hash_table *table,
2020 isl_int *ineq, unsigned len)
2023 struct ineq_cmp_data v;
2024 struct isl_hash_table_entry *entry;
2028 c_hash = isl_seq_get_hash(ineq + 1, len);
2029 entry = isl_hash_table_find(ctx, table, c_hash, has_ineq, &v, 1);
2036 /* Fill hash table "table" with the constraints of "bset".
2037 * Equalities are added as two inequalities.
2038 * The value in the hash table is a pointer to the (in)equality of "bset".
2040 static int hash_basic_set(struct isl_hash_table *table,
2041 struct isl_basic_set *bset)
2044 unsigned dim = isl_basic_set_total_dim(bset);
2046 for (i = 0; i < bset->n_eq; ++i) {
2047 for (j = 0; j < 2; ++j) {
2048 isl_seq_neg(bset->eq[i], bset->eq[i], 1 + dim);
2049 if (hash_ineq(bset->ctx, table, bset->eq[i], dim) < 0)
2053 for (i = 0; i < bset->n_ineq; ++i) {
2054 if (hash_ineq(bset->ctx, table, bset->ineq[i], dim) < 0)
2060 static struct sh_data *sh_data_alloc(struct isl_set *set, unsigned n_ineq)
2062 struct sh_data *data;
2065 data = isl_calloc(set->ctx, struct sh_data,
2066 sizeof(struct sh_data) +
2067 (set->n - 1) * sizeof(struct sh_data_entry));
2070 data->ctx = set->ctx;
2072 data->hull_table = isl_hash_table_alloc(set->ctx, n_ineq);
2073 if (!data->hull_table)
2075 for (i = 0; i < set->n; ++i) {
2076 data->p[i].table = isl_hash_table_alloc(set->ctx,
2077 2 * set->p[i]->n_eq + set->p[i]->n_ineq);
2078 if (!data->p[i].table)
2080 if (hash_basic_set(data->p[i].table, set->p[i]) < 0)
2089 /* Check if inequality "ineq" is a bound for basic set "j" or if
2090 * it can be relaxed (by increasing the constant term) to become
2091 * a bound for that basic set. In the latter case, the constant
2093 * Return 1 if "ineq" is a bound
2094 * 0 if "ineq" may attain arbitrarily small values on basic set "j"
2095 * -1 if some error occurred
2097 static int is_bound(struct sh_data *data, struct isl_set *set, int j,
2100 enum isl_lp_result res;
2103 if (!data->p[j].tab) {
2104 data->p[j].tab = isl_tab_from_basic_set(set->p[j]);
2105 if (!data->p[j].tab)
2111 res = isl_tab_min(data->p[j].tab, ineq, data->ctx->one,
2113 if (res == isl_lp_ok && isl_int_is_neg(opt))
2114 isl_int_sub(ineq[0], ineq[0], opt);
2118 return res == isl_lp_ok ? 1 :
2119 res == isl_lp_unbounded ? 0 : -1;
2122 /* Check if inequality "ineq" from basic set "i" can be relaxed to
2123 * become a bound on the whole set. If so, add the (relaxed) inequality
2126 * We first check if "hull" already contains a translate of the inequality.
2127 * If so, we are done.
2128 * Then, we check if any of the previous basic sets contains a translate
2129 * of the inequality. If so, then we have already considered this
2130 * inequality and we are done.
2131 * Otherwise, for each basic set other than "i", we check if the inequality
2132 * is a bound on the basic set.
2133 * For previous basic sets, we know that they do not contain a translate
2134 * of the inequality, so we directly call is_bound.
2135 * For following basic sets, we first check if a translate of the
2136 * inequality appears in its description and if so directly update
2137 * the inequality accordingly.
2139 static struct isl_basic_set *add_bound(struct isl_basic_set *hull,
2140 struct sh_data *data, struct isl_set *set, int i, isl_int *ineq)
2143 struct ineq_cmp_data v;
2144 struct isl_hash_table_entry *entry;
2150 v.len = isl_basic_set_total_dim(hull);
2152 c_hash = isl_seq_get_hash(ineq + 1, v.len);
2154 entry = isl_hash_table_find(hull->ctx, data->hull_table, c_hash,
2159 for (j = 0; j < i; ++j) {
2160 entry = isl_hash_table_find(hull->ctx, data->p[j].table,
2161 c_hash, has_ineq, &v, 0);
2168 k = isl_basic_set_alloc_inequality(hull);
2169 isl_seq_cpy(hull->ineq[k], ineq, 1 + v.len);
2173 for (j = 0; j < i; ++j) {
2175 bound = is_bound(data, set, j, hull->ineq[k]);
2182 isl_basic_set_free_inequality(hull, 1);
2186 for (j = i + 1; j < set->n; ++j) {
2189 entry = isl_hash_table_find(hull->ctx, data->p[j].table,
2190 c_hash, has_ineq, &v, 0);
2192 ineq_j = entry->data;
2193 neg = isl_seq_is_neg(ineq_j + 1,
2194 hull->ineq[k] + 1, v.len);
2196 isl_int_neg(ineq_j[0], ineq_j[0]);
2197 if (isl_int_gt(ineq_j[0], hull->ineq[k][0]))
2198 isl_int_set(hull->ineq[k][0], ineq_j[0]);
2200 isl_int_neg(ineq_j[0], ineq_j[0]);
2203 bound = is_bound(data, set, j, hull->ineq[k]);
2210 isl_basic_set_free_inequality(hull, 1);
2214 entry = isl_hash_table_find(hull->ctx, data->hull_table, c_hash,
2218 entry->data = hull->ineq[k];
2222 isl_basic_set_free(hull);
2226 /* Check if any inequality from basic set "i" can be relaxed to
2227 * become a bound on the whole set. If so, add the (relaxed) inequality
2230 static struct isl_basic_set *add_bounds(struct isl_basic_set *bset,
2231 struct sh_data *data, struct isl_set *set, int i)
2234 unsigned dim = isl_basic_set_total_dim(bset);
2236 for (j = 0; j < set->p[i]->n_eq; ++j) {
2237 for (k = 0; k < 2; ++k) {
2238 isl_seq_neg(set->p[i]->eq[j], set->p[i]->eq[j], 1+dim);
2239 add_bound(bset, data, set, i, set->p[i]->eq[j]);
2242 for (j = 0; j < set->p[i]->n_ineq; ++j)
2243 add_bound(bset, data, set, i, set->p[i]->ineq[j]);
2247 /* Compute a superset of the convex hull of set that is described
2248 * by only translates of the constraints in the constituents of set.
2250 static struct isl_basic_set *uset_simple_hull(struct isl_set *set)
2252 struct sh_data *data = NULL;
2253 struct isl_basic_set *hull = NULL;
2261 for (i = 0; i < set->n; ++i) {
2264 n_ineq += 2 * set->p[i]->n_eq + set->p[i]->n_ineq;
2267 hull = isl_basic_set_alloc_dim(isl_dim_copy(set->dim), 0, 0, n_ineq);
2271 data = sh_data_alloc(set, n_ineq);
2275 for (i = 0; i < set->n; ++i)
2276 hull = add_bounds(hull, data, set, i);
2284 isl_basic_set_free(hull);
2289 /* Compute a superset of the convex hull of map that is described
2290 * by only translates of the constraints in the constituents of map.
2292 struct isl_basic_map *isl_map_simple_hull(struct isl_map *map)
2294 struct isl_set *set = NULL;
2295 struct isl_basic_map *model = NULL;
2296 struct isl_basic_map *hull;
2297 struct isl_basic_map *affine_hull;
2298 struct isl_basic_set *bset = NULL;
2303 hull = isl_basic_map_empty_like_map(map);
2308 hull = isl_basic_map_copy(map->p[0]);
2313 map = isl_map_detect_equalities(map);
2314 affine_hull = isl_map_affine_hull(isl_map_copy(map));
2315 map = isl_map_align_divs(map);
2316 model = isl_basic_map_copy(map->p[0]);
2318 set = isl_map_underlying_set(map);
2320 bset = uset_simple_hull(set);
2322 hull = isl_basic_map_overlying_set(bset, model);
2324 hull = isl_basic_map_intersect(hull, affine_hull);
2325 hull = isl_basic_map_convex_hull(hull);
2326 ISL_F_SET(hull, ISL_BASIC_MAP_NO_IMPLICIT);
2327 ISL_F_SET(hull, ISL_BASIC_MAP_ALL_EQUALITIES);
2332 struct isl_basic_set *isl_set_simple_hull(struct isl_set *set)
2334 return (struct isl_basic_set *)
2335 isl_map_simple_hull((struct isl_map *)set);
2338 /* Given a set "set", return parametric bounds on the dimension "dim".
2340 static struct isl_basic_set *set_bounds(struct isl_set *set, int dim)
2342 unsigned set_dim = isl_set_dim(set, isl_dim_set);
2343 set = isl_set_copy(set);
2344 set = isl_set_eliminate_dims(set, dim + 1, set_dim - (dim + 1));
2345 set = isl_set_eliminate_dims(set, 0, dim);
2346 return isl_set_convex_hull(set);
2349 /* Computes a "simple hull" and then check if each dimension in the
2350 * resulting hull is bounded by a symbolic constant. If not, the
2351 * hull is intersected with the corresponding bounds on the whole set.
2353 struct isl_basic_set *isl_set_bounded_simple_hull(struct isl_set *set)
2356 struct isl_basic_set *hull;
2357 unsigned nparam, left;
2358 int removed_divs = 0;
2360 hull = isl_set_simple_hull(isl_set_copy(set));
2364 nparam = isl_basic_set_dim(hull, isl_dim_param);
2365 for (i = 0; i < isl_basic_set_dim(hull, isl_dim_set); ++i) {
2366 int lower = 0, upper = 0;
2367 struct isl_basic_set *bounds;
2369 left = isl_basic_set_total_dim(hull) - nparam - i - 1;
2370 for (j = 0; j < hull->n_eq; ++j) {
2371 if (isl_int_is_zero(hull->eq[j][1 + nparam + i]))
2373 if (isl_seq_first_non_zero(hull->eq[j]+1+nparam+i+1,
2380 for (j = 0; j < hull->n_ineq; ++j) {
2381 if (isl_int_is_zero(hull->ineq[j][1 + nparam + i]))
2383 if (isl_seq_first_non_zero(hull->ineq[j]+1+nparam+i+1,
2385 isl_seq_first_non_zero(hull->ineq[j]+1+nparam,
2388 if (isl_int_is_pos(hull->ineq[j][1 + nparam + i]))
2399 if (!removed_divs) {
2400 set = isl_set_remove_divs(set);
2405 bounds = set_bounds(set, i);
2406 hull = isl_basic_set_intersect(hull, bounds);