3 #include "isl_map_private.h"
7 #include "isl_equalities.h"
10 static struct isl_basic_set *uset_convex_hull_wrap_bounded(struct isl_set *set);
12 static void swap_ineq(struct isl_basic_map *bmap, unsigned i, unsigned j)
18 bmap->ineq[i] = bmap->ineq[j];
23 /* Return 1 if constraint c is redundant with respect to the constraints
24 * in bmap. If c is a lower [upper] bound in some variable and bmap
25 * does not have a lower [upper] bound in that variable, then c cannot
26 * be redundant and we do not need solve any lp.
28 int isl_basic_map_constraint_is_redundant(struct isl_basic_map **bmap,
29 isl_int *c, isl_int *opt_n, isl_int *opt_d)
31 enum isl_lp_result res;
38 total = isl_basic_map_total_dim(*bmap);
39 for (i = 0; i < total; ++i) {
41 if (isl_int_is_zero(c[1+i]))
43 sign = isl_int_sgn(c[1+i]);
44 for (j = 0; j < (*bmap)->n_ineq; ++j)
45 if (sign == isl_int_sgn((*bmap)->ineq[j][1+i]))
47 if (j == (*bmap)->n_ineq)
53 res = isl_basic_map_solve_lp(*bmap, 0, c, (*bmap)->ctx->one,
55 if (res == isl_lp_unbounded)
57 if (res == isl_lp_error)
59 if (res == isl_lp_empty) {
60 *bmap = isl_basic_map_set_to_empty(*bmap);
63 return !isl_int_is_neg(*opt_n);
66 int isl_basic_set_constraint_is_redundant(struct isl_basic_set **bset,
67 isl_int *c, isl_int *opt_n, isl_int *opt_d)
69 return isl_basic_map_constraint_is_redundant(
70 (struct isl_basic_map **)bset, c, opt_n, opt_d);
73 /* Compute the convex hull of a basic map, by removing the redundant
74 * constraints. If the minimal value along the normal of a constraint
75 * is the same if the constraint is removed, then the constraint is redundant.
77 * Alternatively, we could have intersected the basic map with the
78 * corresponding equality and the checked if the dimension was that
81 struct isl_basic_map *isl_basic_map_convex_hull(struct isl_basic_map *bmap)
88 bmap = isl_basic_map_gauss(bmap, NULL);
89 if (ISL_F_ISSET(bmap, ISL_BASIC_MAP_EMPTY))
91 if (ISL_F_ISSET(bmap, ISL_BASIC_MAP_NO_REDUNDANT))
93 if (bmap->n_ineq <= 1)
96 tab = isl_tab_from_basic_map(bmap);
97 tab = isl_tab_detect_implicit_equalities(tab);
98 if (isl_tab_detect_redundant(tab) < 0)
100 bmap = isl_basic_map_update_from_tab(bmap, tab);
102 ISL_F_SET(bmap, ISL_BASIC_MAP_NO_IMPLICIT);
103 ISL_F_SET(bmap, ISL_BASIC_MAP_NO_REDUNDANT);
107 isl_basic_map_free(bmap);
111 struct isl_basic_set *isl_basic_set_convex_hull(struct isl_basic_set *bset)
113 return (struct isl_basic_set *)
114 isl_basic_map_convex_hull((struct isl_basic_map *)bset);
117 /* Check if the set set is bound in the direction of the affine
118 * constraint c and if so, set the constant term such that the
119 * resulting constraint is a bounding constraint for the set.
121 static int uset_is_bound(struct isl_set *set, isl_int *c, unsigned len)
129 isl_int_init(opt_denom);
131 for (j = 0; j < set->n; ++j) {
132 enum isl_lp_result res;
134 if (ISL_F_ISSET(set->p[j], ISL_BASIC_SET_EMPTY))
137 res = isl_basic_set_solve_lp(set->p[j],
138 0, c, set->ctx->one, &opt, &opt_denom, NULL);
139 if (res == isl_lp_unbounded)
141 if (res == isl_lp_error)
143 if (res == isl_lp_empty) {
144 set->p[j] = isl_basic_set_set_to_empty(set->p[j]);
149 if (!isl_int_is_one(opt_denom))
150 isl_seq_scale(c, c, opt_denom, len);
151 if (first || isl_int_is_neg(opt))
152 isl_int_sub(c[0], c[0], opt);
156 isl_int_clear(opt_denom);
160 isl_int_clear(opt_denom);
164 /* Check if "c" is a direction that is independent of the previously found "n"
166 * If so, add it to the list, with the negative of the lower bound
167 * in the constant position, i.e., such that c corresponds to a bounding
168 * hyperplane (but not necessarily a facet).
169 * Assumes set "set" is bounded.
171 static int is_independent_bound(struct isl_set *set, isl_int *c,
172 struct isl_mat *dirs, int n)
177 isl_seq_cpy(dirs->row[n]+1, c+1, dirs->n_col-1);
179 int pos = isl_seq_first_non_zero(dirs->row[n]+1, dirs->n_col-1);
182 for (i = 0; i < n; ++i) {
184 pos_i = isl_seq_first_non_zero(dirs->row[i]+1, dirs->n_col-1);
189 isl_seq_elim(dirs->row[n]+1, dirs->row[i]+1, pos,
190 dirs->n_col-1, NULL);
191 pos = isl_seq_first_non_zero(dirs->row[n]+1, dirs->n_col-1);
197 is_bound = uset_is_bound(set, dirs->row[n], dirs->n_col);
202 isl_int *t = dirs->row[n];
203 for (k = n; k > i; --k)
204 dirs->row[k] = dirs->row[k-1];
210 /* Compute and return a maximal set of linearly independent bounds
211 * on the set "set", based on the constraints of the basic sets
214 static struct isl_mat *independent_bounds(struct isl_set *set)
217 struct isl_mat *dirs = NULL;
218 unsigned dim = isl_set_n_dim(set);
220 dirs = isl_mat_alloc(set->ctx, dim, 1+dim);
225 for (i = 0; n < dim && i < set->n; ++i) {
227 struct isl_basic_set *bset = set->p[i];
229 for (j = 0; n < dim && j < bset->n_eq; ++j) {
230 f = is_independent_bound(set, bset->eq[j], dirs, n);
236 for (j = 0; n < dim && j < bset->n_ineq; ++j) {
237 f = is_independent_bound(set, bset->ineq[j], dirs, n);
251 struct isl_basic_set *isl_basic_set_set_rational(struct isl_basic_set *bset)
256 if (ISL_F_ISSET(bset, ISL_BASIC_MAP_RATIONAL))
259 bset = isl_basic_set_cow(bset);
263 ISL_F_SET(bset, ISL_BASIC_MAP_RATIONAL);
265 return isl_basic_set_finalize(bset);
268 static struct isl_set *isl_set_set_rational(struct isl_set *set)
272 set = isl_set_cow(set);
275 for (i = 0; i < set->n; ++i) {
276 set->p[i] = isl_basic_set_set_rational(set->p[i]);
286 static struct isl_basic_set *isl_basic_set_add_equality(
287 struct isl_basic_set *bset, isl_int *c)
292 if (ISL_F_ISSET(bset, ISL_BASIC_SET_EMPTY))
295 isl_assert(bset->ctx, isl_basic_set_n_param(bset) == 0, goto error);
296 isl_assert(bset->ctx, bset->n_div == 0, goto error);
297 dim = isl_basic_set_n_dim(bset);
298 bset = isl_basic_set_cow(bset);
299 bset = isl_basic_set_extend(bset, 0, dim, 0, 1, 0);
300 i = isl_basic_set_alloc_equality(bset);
303 isl_seq_cpy(bset->eq[i], c, 1 + dim);
306 isl_basic_set_free(bset);
310 static struct isl_set *isl_set_add_equality(struct isl_set *set, isl_int *c)
314 set = isl_set_cow(set);
317 for (i = 0; i < set->n; ++i) {
318 set->p[i] = isl_basic_set_add_equality(set->p[i], c);
328 /* Given a union of basic sets, construct the constraints for wrapping
329 * a facet around one of its ridges.
330 * In particular, if each of n the d-dimensional basic sets i in "set"
331 * contains the origin, satisfies the constraints x_1 >= 0 and x_2 >= 0
332 * and is defined by the constraints
336 * then the resulting set is of dimension n*(1+d) and has as constraints
345 static struct isl_basic_set *wrap_constraints(struct isl_set *set)
347 struct isl_basic_set *lp;
351 unsigned dim, lp_dim;
356 dim = 1 + isl_set_n_dim(set);
359 for (i = 0; i < set->n; ++i) {
360 n_eq += set->p[i]->n_eq;
361 n_ineq += set->p[i]->n_ineq;
363 lp = isl_basic_set_alloc(set->ctx, 0, dim * set->n, 0, n_eq, n_ineq);
366 lp_dim = isl_basic_set_n_dim(lp);
367 k = isl_basic_set_alloc_equality(lp);
368 isl_int_set_si(lp->eq[k][0], -1);
369 for (i = 0; i < set->n; ++i) {
370 isl_int_set_si(lp->eq[k][1+dim*i], 0);
371 isl_int_set_si(lp->eq[k][1+dim*i+1], 1);
372 isl_seq_clr(lp->eq[k]+1+dim*i+2, dim-2);
374 for (i = 0; i < set->n; ++i) {
375 k = isl_basic_set_alloc_inequality(lp);
376 isl_seq_clr(lp->ineq[k], 1+lp_dim);
377 isl_int_set_si(lp->ineq[k][1+dim*i], 1);
379 for (j = 0; j < set->p[i]->n_eq; ++j) {
380 k = isl_basic_set_alloc_equality(lp);
381 isl_seq_clr(lp->eq[k], 1+dim*i);
382 isl_seq_cpy(lp->eq[k]+1+dim*i, set->p[i]->eq[j], dim);
383 isl_seq_clr(lp->eq[k]+1+dim*(i+1), dim*(set->n-i-1));
386 for (j = 0; j < set->p[i]->n_ineq; ++j) {
387 k = isl_basic_set_alloc_inequality(lp);
388 isl_seq_clr(lp->ineq[k], 1+dim*i);
389 isl_seq_cpy(lp->ineq[k]+1+dim*i, set->p[i]->ineq[j], dim);
390 isl_seq_clr(lp->ineq[k]+1+dim*(i+1), dim*(set->n-i-1));
396 /* Given a facet "facet" of the convex hull of "set" and a facet "ridge"
397 * of that facet, compute the other facet of the convex hull that contains
400 * We first transform the set such that the facet constraint becomes
404 * I.e., the facet lies in
408 * and on that facet, the constraint that defines the ridge is
412 * (This transformation is not strictly needed, all that is needed is
413 * that the ridge contains the origin.)
415 * Since the ridge contains the origin, the cone of the convex hull
416 * will be of the form
421 * with this second constraint defining the new facet.
422 * The constant a is obtained by settting x_1 in the cone of the
423 * convex hull to 1 and minimizing x_2.
424 * Now, each element in the cone of the convex hull is the sum
425 * of elements in the cones of the basic sets.
426 * If a_i is the dilation factor of basic set i, then the problem
427 * we need to solve is
440 * the constraints of each (transformed) basic set.
441 * If a = n/d, then the constraint defining the new facet (in the transformed
444 * -n x_1 + d x_2 >= 0
446 * In the original space, we need to take the same combination of the
447 * corresponding constraints "facet" and "ridge".
449 * Note that a is always finite, since we only apply the wrapping
450 * technique to a union of polytopes.
452 static isl_int *wrap_facet(struct isl_set *set, isl_int *facet, isl_int *ridge)
455 struct isl_mat *T = NULL;
456 struct isl_basic_set *lp = NULL;
458 enum isl_lp_result res;
462 set = isl_set_copy(set);
464 dim = 1 + isl_set_n_dim(set);
465 T = isl_mat_alloc(set->ctx, 3, dim);
468 isl_int_set_si(T->row[0][0], 1);
469 isl_seq_clr(T->row[0]+1, dim - 1);
470 isl_seq_cpy(T->row[1], facet, dim);
471 isl_seq_cpy(T->row[2], ridge, dim);
472 T = isl_mat_right_inverse(T);
473 set = isl_set_preimage(set, T);
477 lp = wrap_constraints(set);
478 obj = isl_vec_alloc(set->ctx, 1 + dim*set->n);
481 isl_int_set_si(obj->block.data[0], 0);
482 for (i = 0; i < set->n; ++i) {
483 isl_seq_clr(obj->block.data + 1 + dim*i, 2);
484 isl_int_set_si(obj->block.data[1 + dim*i+2], 1);
485 isl_seq_clr(obj->block.data + 1 + dim*i+3, dim-3);
489 res = isl_basic_set_solve_lp(lp, 0,
490 obj->block.data, set->ctx->one, &num, &den, NULL);
491 if (res == isl_lp_ok) {
492 isl_int_neg(num, num);
493 isl_seq_combine(facet, num, facet, den, ridge, dim);
498 isl_basic_set_free(lp);
500 isl_assert(set->ctx, res == isl_lp_ok, return NULL);
503 isl_basic_set_free(lp);
509 /* Given a set of d linearly independent bounding constraints of the
510 * convex hull of "set", compute the constraint of a facet of "set".
512 * We first compute the intersection with the first bounding hyperplane
513 * and remove the component corresponding to this hyperplane from
514 * other bounds (in homogeneous space).
515 * We then wrap around one of the remaining bounding constraints
516 * and continue the process until all bounding constraints have been
517 * taken into account.
518 * The resulting linear combination of the bounding constraints will
519 * correspond to a facet of the convex hull.
521 static struct isl_mat *initial_facet_constraint(struct isl_set *set,
522 struct isl_mat *bounds)
524 struct isl_set *slice = NULL;
525 struct isl_basic_set *face = NULL;
526 struct isl_mat *m, *U, *Q;
528 unsigned dim = isl_set_n_dim(set);
530 isl_assert(set->ctx, set->n > 0, goto error);
531 isl_assert(set->ctx, bounds->n_row == dim, goto error);
533 while (bounds->n_row > 1) {
534 slice = isl_set_copy(set);
535 slice = isl_set_add_equality(slice, bounds->row[0]);
536 face = isl_set_affine_hull(slice);
539 if (face->n_eq == 1) {
540 isl_basic_set_free(face);
543 m = isl_mat_alloc(set->ctx, 1 + face->n_eq, 1 + dim);
546 isl_int_set_si(m->row[0][0], 1);
547 isl_seq_clr(m->row[0]+1, dim);
548 for (i = 0; i < face->n_eq; ++i)
549 isl_seq_cpy(m->row[1 + i], face->eq[i], 1 + dim);
550 U = isl_mat_right_inverse(m);
551 Q = isl_mat_right_inverse(isl_mat_copy(U));
552 U = isl_mat_drop_cols(U, 1 + face->n_eq, dim - face->n_eq);
553 Q = isl_mat_drop_rows(Q, 1 + face->n_eq, dim - face->n_eq);
554 U = isl_mat_drop_cols(U, 0, 1);
555 Q = isl_mat_drop_rows(Q, 0, 1);
556 bounds = isl_mat_product(bounds, U);
557 bounds = isl_mat_product(bounds, Q);
558 while (isl_seq_first_non_zero(bounds->row[bounds->n_row-1],
559 bounds->n_col) == -1) {
561 isl_assert(set->ctx, bounds->n_row > 1, goto error);
563 if (!wrap_facet(set, bounds->row[0],
564 bounds->row[bounds->n_row-1]))
566 isl_basic_set_free(face);
571 isl_basic_set_free(face);
572 isl_mat_free(bounds);
576 /* Given the bounding constraint "c" of a facet of the convex hull of "set",
577 * compute a hyperplane description of the facet, i.e., compute the facets
580 * We compute an affine transformation that transforms the constraint
589 * by computing the right inverse U of a matrix that starts with the rows
602 * Since z_1 is zero, we can drop this variable as well as the corresponding
603 * column of U to obtain
611 * with Q' equal to Q, but without the corresponding row.
612 * After computing the facets of the facet in the z' space,
613 * we convert them back to the x space through Q.
615 static struct isl_basic_set *compute_facet(struct isl_set *set, isl_int *c)
617 struct isl_mat *m, *U, *Q;
618 struct isl_basic_set *facet = NULL;
623 set = isl_set_copy(set);
624 dim = isl_set_n_dim(set);
625 m = isl_mat_alloc(set->ctx, 2, 1 + dim);
628 isl_int_set_si(m->row[0][0], 1);
629 isl_seq_clr(m->row[0]+1, dim);
630 isl_seq_cpy(m->row[1], c, 1+dim);
631 U = isl_mat_right_inverse(m);
632 Q = isl_mat_right_inverse(isl_mat_copy(U));
633 U = isl_mat_drop_cols(U, 1, 1);
634 Q = isl_mat_drop_rows(Q, 1, 1);
635 set = isl_set_preimage(set, U);
636 facet = uset_convex_hull_wrap_bounded(set);
637 facet = isl_basic_set_preimage(facet, Q);
638 isl_assert(ctx, facet->n_eq == 0, goto error);
641 isl_basic_set_free(facet);
646 /* Given an initial facet constraint, compute the remaining facets.
647 * We do this by running through all facets found so far and computing
648 * the adjacent facets through wrapping, adding those facets that we
649 * hadn't already found before.
651 * For each facet we have found so far, we first compute its facets
652 * in the resulting convex hull. That is, we compute the ridges
653 * of the resulting convex hull contained in the facet.
654 * We also compute the corresponding facet in the current approximation
655 * of the convex hull. There is no need to wrap around the ridges
656 * in this facet since that would result in a facet that is already
657 * present in the current approximation.
659 * This function can still be significantly optimized by checking which of
660 * the facets of the basic sets are also facets of the convex hull and
661 * using all the facets so far to help in constructing the facets of the
664 * using the technique in section "3.1 Ridge Generation" of
665 * "Extended Convex Hull" by Fukuda et al.
667 static struct isl_basic_set *extend(struct isl_basic_set *hull,
672 struct isl_basic_set *facet = NULL;
673 struct isl_basic_set *hull_facet = NULL;
676 isl_assert(set->ctx, set->n > 0, goto error);
678 dim = isl_set_n_dim(set);
680 for (i = 0; i < hull->n_ineq; ++i) {
681 facet = compute_facet(set, hull->ineq[i]);
682 facet = isl_basic_set_add_equality(facet, hull->ineq[i]);
683 facet = isl_basic_set_gauss(facet, NULL);
684 facet = isl_basic_set_normalize_constraints(facet);
685 hull_facet = isl_basic_set_copy(hull);
686 hull_facet = isl_basic_set_add_equality(hull_facet, hull->ineq[i]);
687 hull_facet = isl_basic_set_gauss(hull_facet, NULL);
688 hull_facet = isl_basic_set_normalize_constraints(hull_facet);
691 hull = isl_basic_set_cow(hull);
692 hull = isl_basic_set_extend_dim(hull,
693 isl_dim_copy(hull->dim), 0, 0, facet->n_ineq);
694 for (j = 0; j < facet->n_ineq; ++j) {
695 for (f = 0; f < hull_facet->n_ineq; ++f)
696 if (isl_seq_eq(facet->ineq[j],
697 hull_facet->ineq[f], 1 + dim))
699 if (f < hull_facet->n_ineq)
701 k = isl_basic_set_alloc_inequality(hull);
704 isl_seq_cpy(hull->ineq[k], hull->ineq[i], 1+dim);
705 if (!wrap_facet(set, hull->ineq[k], facet->ineq[j]))
708 isl_basic_set_free(hull_facet);
709 isl_basic_set_free(facet);
711 hull = isl_basic_set_simplify(hull);
712 hull = isl_basic_set_finalize(hull);
715 isl_basic_set_free(hull_facet);
716 isl_basic_set_free(facet);
717 isl_basic_set_free(hull);
721 /* Special case for computing the convex hull of a one dimensional set.
722 * We simply collect the lower and upper bounds of each basic set
723 * and the biggest of those.
725 static struct isl_basic_set *convex_hull_1d(struct isl_set *set)
727 struct isl_mat *c = NULL;
728 isl_int *lower = NULL;
729 isl_int *upper = NULL;
732 struct isl_basic_set *hull;
734 for (i = 0; i < set->n; ++i) {
735 set->p[i] = isl_basic_set_simplify(set->p[i]);
739 set = isl_set_remove_empty_parts(set);
742 isl_assert(set->ctx, set->n > 0, goto error);
743 c = isl_mat_alloc(set->ctx, 2, 2);
747 if (set->p[0]->n_eq > 0) {
748 isl_assert(set->ctx, set->p[0]->n_eq == 1, goto error);
751 if (isl_int_is_pos(set->p[0]->eq[0][1])) {
752 isl_seq_cpy(lower, set->p[0]->eq[0], 2);
753 isl_seq_neg(upper, set->p[0]->eq[0], 2);
755 isl_seq_neg(lower, set->p[0]->eq[0], 2);
756 isl_seq_cpy(upper, set->p[0]->eq[0], 2);
759 for (j = 0; j < set->p[0]->n_ineq; ++j) {
760 if (isl_int_is_pos(set->p[0]->ineq[j][1])) {
762 isl_seq_cpy(lower, set->p[0]->ineq[j], 2);
765 isl_seq_cpy(upper, set->p[0]->ineq[j], 2);
772 for (i = 0; i < set->n; ++i) {
773 struct isl_basic_set *bset = set->p[i];
777 for (j = 0; j < bset->n_eq; ++j) {
781 isl_int_mul(a, lower[0], bset->eq[j][1]);
782 isl_int_mul(b, lower[1], bset->eq[j][0]);
783 if (isl_int_lt(a, b) && isl_int_is_pos(bset->eq[j][1]))
784 isl_seq_cpy(lower, bset->eq[j], 2);
785 if (isl_int_gt(a, b) && isl_int_is_neg(bset->eq[j][1]))
786 isl_seq_neg(lower, bset->eq[j], 2);
789 isl_int_mul(a, upper[0], bset->eq[j][1]);
790 isl_int_mul(b, upper[1], bset->eq[j][0]);
791 if (isl_int_lt(a, b) && isl_int_is_pos(bset->eq[j][1]))
792 isl_seq_neg(upper, bset->eq[j], 2);
793 if (isl_int_gt(a, b) && isl_int_is_neg(bset->eq[j][1]))
794 isl_seq_cpy(upper, bset->eq[j], 2);
797 for (j = 0; j < bset->n_ineq; ++j) {
798 if (isl_int_is_pos(bset->ineq[j][1]))
800 if (isl_int_is_neg(bset->ineq[j][1]))
802 if (lower && isl_int_is_pos(bset->ineq[j][1])) {
803 isl_int_mul(a, lower[0], bset->ineq[j][1]);
804 isl_int_mul(b, lower[1], bset->ineq[j][0]);
805 if (isl_int_lt(a, b))
806 isl_seq_cpy(lower, bset->ineq[j], 2);
808 if (upper && isl_int_is_neg(bset->ineq[j][1])) {
809 isl_int_mul(a, upper[0], bset->ineq[j][1]);
810 isl_int_mul(b, upper[1], bset->ineq[j][0]);
811 if (isl_int_gt(a, b))
812 isl_seq_cpy(upper, bset->ineq[j], 2);
823 hull = isl_basic_set_alloc(set->ctx, 0, 1, 0, 0, 2);
824 hull = isl_basic_set_set_rational(hull);
828 k = isl_basic_set_alloc_inequality(hull);
829 isl_seq_cpy(hull->ineq[k], lower, 2);
832 k = isl_basic_set_alloc_inequality(hull);
833 isl_seq_cpy(hull->ineq[k], upper, 2);
835 hull = isl_basic_set_finalize(hull);
845 /* Project out final n dimensions using Fourier-Motzkin */
846 static struct isl_set *set_project_out(struct isl_ctx *ctx,
847 struct isl_set *set, unsigned n)
849 return isl_set_remove_dims(set, isl_set_n_dim(set) - n, n);
852 static struct isl_basic_set *convex_hull_0d(struct isl_set *set)
854 struct isl_basic_set *convex_hull;
859 if (isl_set_is_empty(set))
860 convex_hull = isl_basic_set_empty(isl_dim_copy(set->dim));
862 convex_hull = isl_basic_set_universe(isl_dim_copy(set->dim));
867 /* Compute the convex hull of a pair of basic sets without any parameters or
868 * integer divisions using Fourier-Motzkin elimination.
869 * The convex hull is the set of all points that can be written as
870 * the sum of points from both basic sets (in homogeneous coordinates).
871 * We set up the constraints in a space with dimensions for each of
872 * the three sets and then project out the dimensions corresponding
873 * to the two original basic sets, retaining only those corresponding
874 * to the convex hull.
876 static struct isl_basic_set *convex_hull_pair_elim(struct isl_basic_set *bset1,
877 struct isl_basic_set *bset2)
880 struct isl_basic_set *bset[2];
881 struct isl_basic_set *hull = NULL;
884 if (!bset1 || !bset2)
887 dim = isl_basic_set_n_dim(bset1);
888 hull = isl_basic_set_alloc(bset1->ctx, 0, 2 + 3 * dim, 0,
889 1 + dim + bset1->n_eq + bset2->n_eq,
890 2 + bset1->n_ineq + bset2->n_ineq);
893 for (i = 0; i < 2; ++i) {
894 for (j = 0; j < bset[i]->n_eq; ++j) {
895 k = isl_basic_set_alloc_equality(hull);
898 isl_seq_clr(hull->eq[k], (i+1) * (1+dim));
899 isl_seq_clr(hull->eq[k]+(i+2)*(1+dim), (1-i)*(1+dim));
900 isl_seq_cpy(hull->eq[k]+(i+1)*(1+dim), bset[i]->eq[j],
903 for (j = 0; j < bset[i]->n_ineq; ++j) {
904 k = isl_basic_set_alloc_inequality(hull);
907 isl_seq_clr(hull->ineq[k], (i+1) * (1+dim));
908 isl_seq_clr(hull->ineq[k]+(i+2)*(1+dim), (1-i)*(1+dim));
909 isl_seq_cpy(hull->ineq[k]+(i+1)*(1+dim),
910 bset[i]->ineq[j], 1+dim);
912 k = isl_basic_set_alloc_inequality(hull);
915 isl_seq_clr(hull->ineq[k], 1+2+3*dim);
916 isl_int_set_si(hull->ineq[k][(i+1)*(1+dim)], 1);
918 for (j = 0; j < 1+dim; ++j) {
919 k = isl_basic_set_alloc_equality(hull);
922 isl_seq_clr(hull->eq[k], 1+2+3*dim);
923 isl_int_set_si(hull->eq[k][j], -1);
924 isl_int_set_si(hull->eq[k][1+dim+j], 1);
925 isl_int_set_si(hull->eq[k][2*(1+dim)+j], 1);
927 hull = isl_basic_set_set_rational(hull);
928 hull = isl_basic_set_remove_dims(hull, dim, 2*(1+dim));
929 hull = isl_basic_set_convex_hull(hull);
930 isl_basic_set_free(bset1);
931 isl_basic_set_free(bset2);
934 isl_basic_set_free(bset1);
935 isl_basic_set_free(bset2);
936 isl_basic_set_free(hull);
940 static int isl_basic_set_is_bounded(struct isl_basic_set *bset)
945 tab = isl_tab_from_recession_cone(bset);
946 bounded = isl_tab_cone_is_bounded(tab);
951 static int isl_set_is_bounded(struct isl_set *set)
955 for (i = 0; i < set->n; ++i) {
956 int bounded = isl_basic_set_is_bounded(set->p[i]);
957 if (!bounded || bounded < 0)
963 /* Compute the lineality space of the convex hull of bset1 and bset2.
965 * We first compute the intersection of the recession cone of bset1
966 * with the negative of the recession cone of bset2 and then compute
967 * the linear hull of the resulting cone.
969 static struct isl_basic_set *induced_lineality_space(
970 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
973 struct isl_basic_set *lin = NULL;
976 if (!bset1 || !bset2)
979 dim = isl_basic_set_total_dim(bset1);
980 lin = isl_basic_set_alloc_dim(isl_basic_set_get_dim(bset1), 0,
981 bset1->n_eq + bset2->n_eq,
982 bset1->n_ineq + bset2->n_ineq);
983 lin = isl_basic_set_set_rational(lin);
986 for (i = 0; i < bset1->n_eq; ++i) {
987 k = isl_basic_set_alloc_equality(lin);
990 isl_int_set_si(lin->eq[k][0], 0);
991 isl_seq_cpy(lin->eq[k] + 1, bset1->eq[i] + 1, dim);
993 for (i = 0; i < bset1->n_ineq; ++i) {
994 k = isl_basic_set_alloc_inequality(lin);
997 isl_int_set_si(lin->ineq[k][0], 0);
998 isl_seq_cpy(lin->ineq[k] + 1, bset1->ineq[i] + 1, dim);
1000 for (i = 0; i < bset2->n_eq; ++i) {
1001 k = isl_basic_set_alloc_equality(lin);
1004 isl_int_set_si(lin->eq[k][0], 0);
1005 isl_seq_neg(lin->eq[k] + 1, bset2->eq[i] + 1, dim);
1007 for (i = 0; i < bset2->n_ineq; ++i) {
1008 k = isl_basic_set_alloc_inequality(lin);
1011 isl_int_set_si(lin->ineq[k][0], 0);
1012 isl_seq_neg(lin->ineq[k] + 1, bset2->ineq[i] + 1, dim);
1015 isl_basic_set_free(bset1);
1016 isl_basic_set_free(bset2);
1017 return isl_basic_set_affine_hull(lin);
1019 isl_basic_set_free(lin);
1020 isl_basic_set_free(bset1);
1021 isl_basic_set_free(bset2);
1025 static struct isl_basic_set *uset_convex_hull(struct isl_set *set);
1027 /* Given a set and a linear space "lin" of dimension n > 0,
1028 * project the linear space from the set, compute the convex hull
1029 * and then map the set back to the original space.
1035 * describe the linear space. We first compute the Hermite normal
1036 * form H = M U of M = H Q, to obtain
1040 * The last n rows of H will be zero, so the last n variables of x' = Q x
1041 * are the one we want to project out. We do this by transforming each
1042 * basic set A x >= b to A U x' >= b and then removing the last n dimensions.
1043 * After computing the convex hull in x'_1, i.e., A' x'_1 >= b',
1044 * we transform the hull back to the original space as A' Q_1 x >= b',
1045 * with Q_1 all but the last n rows of Q.
1047 static struct isl_basic_set *modulo_lineality(struct isl_set *set,
1048 struct isl_basic_set *lin)
1050 unsigned total = isl_basic_set_total_dim(lin);
1052 struct isl_basic_set *hull;
1053 struct isl_mat *M, *U, *Q;
1057 lin_dim = total - lin->n_eq;
1058 M = isl_mat_sub_alloc(set->ctx, lin->eq, 0, lin->n_eq, 1, total);
1059 M = isl_mat_left_hermite(M, 0, &U, &Q);
1063 isl_basic_set_free(lin);
1065 Q = isl_mat_drop_rows(Q, Q->n_row - lin_dim, lin_dim);
1067 U = isl_mat_lin_to_aff(U);
1068 Q = isl_mat_lin_to_aff(Q);
1070 set = isl_set_preimage(set, U);
1071 set = isl_set_remove_dims(set, total - lin_dim, lin_dim);
1072 hull = uset_convex_hull(set);
1073 hull = isl_basic_set_preimage(hull, Q);
1077 isl_basic_set_free(lin);
1082 /* Given two polyhedra with as constraints h_{ij} x >= 0 in homegeneous space,
1083 * set up an LP for solving
1085 * \sum_j \alpha_{1j} h_{1j} = \sum_j \alpha_{2j} h_{2j}
1087 * \alpha{i0} corresponds to the (implicit) positivity constraint 1 >= 0
1088 * The next \alpha{ij} correspond to the equalities and come in pairs.
1089 * The final \alpha{ij} correspond to the inequalities.
1091 static struct isl_basic_set *valid_direction_lp(
1092 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1094 struct isl_dim *dim;
1095 struct isl_basic_set *lp;
1100 if (!bset1 || !bset2)
1102 d = 1 + isl_basic_set_total_dim(bset1);
1104 2 * bset1->n_eq + bset1->n_ineq + 2 * bset2->n_eq + bset2->n_ineq;
1105 dim = isl_dim_set_alloc(bset1->ctx, 0, n);
1106 lp = isl_basic_set_alloc_dim(dim, 0, d, n);
1109 for (i = 0; i < n; ++i) {
1110 k = isl_basic_set_alloc_inequality(lp);
1113 isl_seq_clr(lp->ineq[k] + 1, n);
1114 isl_int_set_si(lp->ineq[k][0], -1);
1115 isl_int_set_si(lp->ineq[k][1 + i], 1);
1117 for (i = 0; i < d; ++i) {
1118 k = isl_basic_set_alloc_equality(lp);
1122 isl_int_set_si(lp->eq[k][n++], 0);
1123 /* positivity constraint 1 >= 0 */
1124 isl_int_set_si(lp->eq[k][n++], i == 0);
1125 for (j = 0; j < bset1->n_eq; ++j) {
1126 isl_int_set(lp->eq[k][n++], bset1->eq[j][i]);
1127 isl_int_neg(lp->eq[k][n++], bset1->eq[j][i]);
1129 for (j = 0; j < bset1->n_ineq; ++j)
1130 isl_int_set(lp->eq[k][n++], bset1->ineq[j][i]);
1131 /* positivity constraint 1 >= 0 */
1132 isl_int_set_si(lp->eq[k][n++], -(i == 0));
1133 for (j = 0; j < bset2->n_eq; ++j) {
1134 isl_int_neg(lp->eq[k][n++], bset2->eq[j][i]);
1135 isl_int_set(lp->eq[k][n++], bset2->eq[j][i]);
1137 for (j = 0; j < bset2->n_ineq; ++j)
1138 isl_int_neg(lp->eq[k][n++], bset2->ineq[j][i]);
1140 lp = isl_basic_set_gauss(lp, NULL);
1141 isl_basic_set_free(bset1);
1142 isl_basic_set_free(bset2);
1145 isl_basic_set_free(bset1);
1146 isl_basic_set_free(bset2);
1150 /* Compute a vector s in the homogeneous space such that <s, r> > 0
1151 * for all rays in the homogeneous space of the two cones that correspond
1152 * to the input polyhedra bset1 and bset2.
1154 * We compute s as a vector that satisfies
1156 * s = \sum_j \alpha_{ij} h_{ij} for i = 1,2 (*)
1158 * with h_{ij} the normals of the facets of polyhedron i
1159 * (including the "positivity constraint" 1 >= 0) and \alpha_{ij}
1160 * strictly positive numbers. For simplicity we impose \alpha_{ij} >= 1.
1161 * We first set up an LP with as variables the \alpha{ij}.
1162 * In this formulateion, for each polyhedron i,
1163 * the first constraint is the positivity constraint, followed by pairs
1164 * of variables for the equalities, followed by variables for the inequalities.
1165 * We then simply pick a feasible solution and compute s using (*).
1167 * Note that we simply pick any valid direction and make no attempt
1168 * to pick a "good" or even the "best" valid direction.
1170 static struct isl_vec *valid_direction(
1171 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1173 struct isl_basic_set *lp;
1174 struct isl_tab *tab;
1175 struct isl_vec *sample = NULL;
1176 struct isl_vec *dir;
1181 if (!bset1 || !bset2)
1183 lp = valid_direction_lp(isl_basic_set_copy(bset1),
1184 isl_basic_set_copy(bset2));
1185 tab = isl_tab_from_basic_set(lp);
1186 sample = isl_tab_get_sample_value(tab);
1188 isl_basic_set_free(lp);
1191 d = isl_basic_set_total_dim(bset1);
1192 dir = isl_vec_alloc(bset1->ctx, 1 + d);
1195 isl_seq_clr(dir->block.data + 1, dir->size - 1);
1197 /* positivity constraint 1 >= 0 */
1198 isl_int_set(dir->block.data[0], sample->block.data[n++]);
1199 for (i = 0; i < bset1->n_eq; ++i) {
1200 isl_int_sub(sample->block.data[n],
1201 sample->block.data[n], sample->block.data[n+1]);
1202 isl_seq_combine(dir->block.data,
1203 bset1->ctx->one, dir->block.data,
1204 sample->block.data[n], bset1->eq[i], 1 + d);
1208 for (i = 0; i < bset1->n_ineq; ++i)
1209 isl_seq_combine(dir->block.data,
1210 bset1->ctx->one, dir->block.data,
1211 sample->block.data[n++], bset1->ineq[i], 1 + d);
1212 isl_vec_free(sample);
1213 isl_seq_normalize(bset1->ctx, dir->block.data + 1, dir->size - 1);
1214 isl_basic_set_free(bset1);
1215 isl_basic_set_free(bset2);
1218 isl_vec_free(sample);
1219 isl_basic_set_free(bset1);
1220 isl_basic_set_free(bset2);
1224 /* Given a polyhedron b_i + A_i x >= 0 and a map T = S^{-1},
1225 * compute b_i' + A_i' x' >= 0, with
1227 * [ b_i A_i ] [ y' ] [ y' ]
1228 * [ 1 0 ] S^{-1} [ x' ] >= 0 or [ b_i' A_i' ] [ x' ] >= 0
1230 * In particular, add the "positivity constraint" and then perform
1233 static struct isl_basic_set *homogeneous_map(struct isl_basic_set *bset,
1240 bset = isl_basic_set_extend_constraints(bset, 0, 1);
1241 k = isl_basic_set_alloc_inequality(bset);
1244 isl_seq_clr(bset->ineq[k] + 1, isl_basic_set_total_dim(bset));
1245 isl_int_set_si(bset->ineq[k][0], 1);
1246 bset = isl_basic_set_preimage(bset, T);
1250 isl_basic_set_free(bset);
1254 /* Compute the convex hull of a pair of basic sets without any parameters or
1255 * integer divisions, where the convex hull is known to be pointed,
1256 * but the basic sets may be unbounded.
1258 * We turn this problem into the computation of a convex hull of a pair
1259 * _bounded_ polyhedra by "changing the direction of the homogeneous
1260 * dimension". This idea is due to Matthias Koeppe.
1262 * Consider the cones in homogeneous space that correspond to the
1263 * input polyhedra. The rays of these cones are also rays of the
1264 * polyhedra if the coordinate that corresponds to the homogeneous
1265 * dimension is zero. That is, if the inner product of the rays
1266 * with the homogeneous direction is zero.
1267 * The cones in the homogeneous space can also be considered to
1268 * correspond to other pairs of polyhedra by chosing a different
1269 * homogeneous direction. To ensure that both of these polyhedra
1270 * are bounded, we need to make sure that all rays of the cones
1271 * correspond to vertices and not to rays.
1272 * Let s be a direction such that <s, r> > 0 for all rays r of both cones.
1273 * Then using s as a homogeneous direction, we obtain a pair of polytopes.
1274 * The vector s is computed in valid_direction.
1276 * Note that we need to consider _all_ rays of the cones and not just
1277 * the rays that correspond to rays in the polyhedra. If we were to
1278 * only consider those rays and turn them into vertices, then we
1279 * may inadvertently turn some vertices into rays.
1281 * The standard homogeneous direction is the unit vector in the 0th coordinate.
1282 * We therefore transform the two polyhedra such that the selected
1283 * direction is mapped onto this standard direction and then proceed
1284 * with the normal computation.
1285 * Let S be a non-singular square matrix with s as its first row,
1286 * then we want to map the polyhedra to the space
1288 * [ y' ] [ y ] [ y ] [ y' ]
1289 * [ x' ] = S [ x ] i.e., [ x ] = S^{-1} [ x' ]
1291 * We take S to be the unimodular completion of s to limit the growth
1292 * of the coefficients in the following computations.
1294 * Let b_i + A_i x >= 0 be the constraints of polyhedron i.
1295 * We first move to the homogeneous dimension
1297 * b_i y + A_i x >= 0 [ b_i A_i ] [ y ] [ 0 ]
1298 * y >= 0 or [ 1 0 ] [ x ] >= [ 0 ]
1300 * Then we change directoin
1302 * [ b_i A_i ] [ y' ] [ y' ]
1303 * [ 1 0 ] S^{-1} [ x' ] >= 0 or [ b_i' A_i' ] [ x' ] >= 0
1305 * Then we compute the convex hull of the polytopes b_i' + A_i' x' >= 0
1306 * resulting in b' + A' x' >= 0, which we then convert back
1309 * [ b' A' ] S [ x ] >= 0 or [ b A ] [ x ] >= 0
1311 * The polyhedron b + A x >= 0 is then the convex hull of the input polyhedra.
1313 static struct isl_basic_set *convex_hull_pair_pointed(
1314 struct isl_basic_set *bset1, struct isl_basic_set *bset2)
1316 struct isl_ctx *ctx = NULL;
1317 struct isl_vec *dir = NULL;
1318 struct isl_mat *T = NULL;
1319 struct isl_mat *T2 = NULL;
1320 struct isl_basic_set *hull;
1321 struct isl_set *set;
1323 if (!bset1 || !bset2)
1326 dir = valid_direction(isl_basic_set_copy(bset1),
1327 isl_basic_set_copy(bset2));
1330 T = isl_mat_alloc(bset1->ctx, dir->size, dir->size);
1333 isl_seq_cpy(T->row[0], dir->block.data, dir->size);
1334 T = isl_mat_unimodular_complete(T, 1);
1335 T2 = isl_mat_right_inverse(isl_mat_copy(T));
1337 bset1 = homogeneous_map(bset1, isl_mat_copy(T2));
1338 bset2 = homogeneous_map(bset2, T2);
1339 set = isl_set_alloc_dim(isl_basic_set_get_dim(bset1), 2, 0);
1340 set = isl_set_add(set, bset1);
1341 set = isl_set_add(set, bset2);
1342 hull = uset_convex_hull(set);
1343 hull = isl_basic_set_preimage(hull, T);
1350 isl_basic_set_free(bset1);
1351 isl_basic_set_free(bset2);
1355 /* Compute the convex hull of a pair of basic sets without any parameters or
1356 * integer divisions.
1358 * If the convex hull of the two basic sets would have a non-trivial
1359 * lineality space, we first project out this lineality space.
1361 static struct isl_basic_set *convex_hull_pair(struct isl_basic_set *bset1,
1362 struct isl_basic_set *bset2)
1364 struct isl_basic_set *lin;
1366 if (isl_basic_set_is_bounded(bset1) || isl_basic_set_is_bounded(bset2))
1367 return convex_hull_pair_pointed(bset1, bset2);
1369 lin = induced_lineality_space(isl_basic_set_copy(bset1),
1370 isl_basic_set_copy(bset2));
1373 if (isl_basic_set_is_universe(lin)) {
1374 isl_basic_set_free(bset1);
1375 isl_basic_set_free(bset2);
1378 if (lin->n_eq < isl_basic_set_total_dim(lin)) {
1379 struct isl_set *set;
1380 set = isl_set_alloc_dim(isl_basic_set_get_dim(bset1), 2, 0);
1381 set = isl_set_add(set, bset1);
1382 set = isl_set_add(set, bset2);
1383 return modulo_lineality(set, lin);
1385 isl_basic_set_free(lin);
1387 return convex_hull_pair_pointed(bset1, bset2);
1389 isl_basic_set_free(bset1);
1390 isl_basic_set_free(bset2);
1394 /* Compute the lineality space of a basic set.
1395 * We currently do not allow the basic set to have any divs.
1396 * We basically just drop the constants and turn every inequality
1399 struct isl_basic_set *isl_basic_set_lineality_space(struct isl_basic_set *bset)
1402 struct isl_basic_set *lin = NULL;
1407 isl_assert(bset->ctx, bset->n_div == 0, goto error);
1408 dim = isl_basic_set_total_dim(bset);
1410 lin = isl_basic_set_alloc_dim(isl_basic_set_get_dim(bset), 0, dim, 0);
1413 for (i = 0; i < bset->n_eq; ++i) {
1414 k = isl_basic_set_alloc_equality(lin);
1417 isl_int_set_si(lin->eq[k][0], 0);
1418 isl_seq_cpy(lin->eq[k] + 1, bset->eq[i] + 1, dim);
1420 lin = isl_basic_set_gauss(lin, NULL);
1423 for (i = 0; i < bset->n_ineq && lin->n_eq < dim; ++i) {
1424 k = isl_basic_set_alloc_equality(lin);
1427 isl_int_set_si(lin->eq[k][0], 0);
1428 isl_seq_cpy(lin->eq[k] + 1, bset->ineq[i] + 1, dim);
1429 lin = isl_basic_set_gauss(lin, NULL);
1433 isl_basic_set_free(bset);
1436 isl_basic_set_free(lin);
1437 isl_basic_set_free(bset);
1441 /* Compute the (linear) hull of the lineality spaces of the basic sets in the
1442 * "underlying" set "set".
1444 static struct isl_basic_set *uset_combined_lineality_space(struct isl_set *set)
1447 struct isl_set *lin = NULL;
1452 struct isl_dim *dim = isl_set_get_dim(set);
1454 return isl_basic_set_empty(dim);
1457 lin = isl_set_alloc_dim(isl_set_get_dim(set), set->n, 0);
1458 for (i = 0; i < set->n; ++i)
1459 lin = isl_set_add(lin,
1460 isl_basic_set_lineality_space(isl_basic_set_copy(set->p[i])));
1462 return isl_set_affine_hull(lin);
1465 /* Compute the convex hull of a set without any parameters or
1466 * integer divisions.
1467 * In each step, we combined two basic sets until only one
1468 * basic set is left.
1469 * The input basic sets are assumed not to have a non-trivial
1470 * lineality space. If any of the intermediate results has
1471 * a non-trivial lineality space, it is projected out.
1473 static struct isl_basic_set *uset_convex_hull_unbounded(struct isl_set *set)
1475 struct isl_basic_set *convex_hull = NULL;
1477 convex_hull = isl_set_copy_basic_set(set);
1478 set = isl_set_drop_basic_set(set, convex_hull);
1481 while (set->n > 0) {
1482 struct isl_basic_set *t;
1483 t = isl_set_copy_basic_set(set);
1486 set = isl_set_drop_basic_set(set, t);
1489 convex_hull = convex_hull_pair(convex_hull, t);
1492 t = isl_basic_set_lineality_space(isl_basic_set_copy(convex_hull));
1495 if (isl_basic_set_is_universe(t)) {
1496 isl_basic_set_free(convex_hull);
1500 if (t->n_eq < isl_basic_set_total_dim(t)) {
1501 set = isl_set_add(set, convex_hull);
1502 return modulo_lineality(set, t);
1504 isl_basic_set_free(t);
1510 isl_basic_set_free(convex_hull);
1514 /* Compute an initial hull for wrapping containing a single initial
1515 * facet by first computing bounds on the set and then using these
1516 * bounds to construct an initial facet.
1517 * This function is a remnant of an older implementation where the
1518 * bounds were also used to check whether the set was bounded.
1519 * Since this function will now only be called when we know the
1520 * set to be bounded, the initial facet should probably be constructed
1521 * by simply using the coordinate directions instead.
1523 static struct isl_basic_set *initial_hull(struct isl_basic_set *hull,
1524 struct isl_set *set)
1526 struct isl_mat *bounds = NULL;
1532 bounds = independent_bounds(set);
1535 isl_assert(set->ctx, bounds->n_row == isl_set_n_dim(set), goto error);
1536 bounds = initial_facet_constraint(set, bounds);
1539 k = isl_basic_set_alloc_inequality(hull);
1542 dim = isl_set_n_dim(set);
1543 isl_assert(set->ctx, 1 + dim == bounds->n_col, goto error);
1544 isl_seq_cpy(hull->ineq[k], bounds->row[0], bounds->n_col);
1545 isl_mat_free(bounds);
1549 isl_basic_set_free(hull);
1550 isl_mat_free(bounds);
1554 struct max_constraint {
1560 static int max_constraint_equal(const void *entry, const void *val)
1562 struct max_constraint *a = (struct max_constraint *)entry;
1563 isl_int *b = (isl_int *)val;
1565 return isl_seq_eq(a->c->row[0] + 1, b, a->c->n_col - 1);
1568 static void update_constraint(struct isl_ctx *ctx, struct isl_hash_table *table,
1569 isl_int *con, unsigned len, int n, int ineq)
1571 struct isl_hash_table_entry *entry;
1572 struct max_constraint *c;
1575 c_hash = isl_seq_get_hash(con + 1, len);
1576 entry = isl_hash_table_find(ctx, table, c_hash, max_constraint_equal,
1582 isl_hash_table_remove(ctx, table, entry);
1586 if (isl_int_gt(c->c->row[0][0], con[0]))
1588 if (isl_int_eq(c->c->row[0][0], con[0])) {
1593 c->c = isl_mat_cow(c->c);
1594 isl_int_set(c->c->row[0][0], con[0]);
1598 /* Check whether the constraint hash table "table" constains the constraint
1601 static int has_constraint(struct isl_ctx *ctx, struct isl_hash_table *table,
1602 isl_int *con, unsigned len, int n)
1604 struct isl_hash_table_entry *entry;
1605 struct max_constraint *c;
1608 c_hash = isl_seq_get_hash(con + 1, len);
1609 entry = isl_hash_table_find(ctx, table, c_hash, max_constraint_equal,
1616 return isl_int_eq(c->c->row[0][0], con[0]);
1619 /* Check for inequality constraints of a basic set without equalities
1620 * such that the same or more stringent copies of the constraint appear
1621 * in all of the basic sets. Such constraints are necessarily facet
1622 * constraints of the convex hull.
1624 * If the resulting basic set is by chance identical to one of
1625 * the basic sets in "set", then we know that this basic set contains
1626 * all other basic sets and is therefore the convex hull of set.
1627 * In this case we set *is_hull to 1.
1629 static struct isl_basic_set *common_constraints(struct isl_basic_set *hull,
1630 struct isl_set *set, int *is_hull)
1633 int min_constraints;
1635 struct max_constraint *constraints = NULL;
1636 struct isl_hash_table *table = NULL;
1641 for (i = 0; i < set->n; ++i)
1642 if (set->p[i]->n_eq == 0)
1646 min_constraints = set->p[i]->n_ineq;
1648 for (i = best + 1; i < set->n; ++i) {
1649 if (set->p[i]->n_eq != 0)
1651 if (set->p[i]->n_ineq >= min_constraints)
1653 min_constraints = set->p[i]->n_ineq;
1656 constraints = isl_calloc_array(hull->ctx, struct max_constraint,
1660 table = isl_alloc_type(hull->ctx, struct isl_hash_table);
1661 if (isl_hash_table_init(hull->ctx, table, min_constraints))
1664 total = isl_dim_total(set->dim);
1665 for (i = 0; i < set->p[best]->n_ineq; ++i) {
1666 constraints[i].c = isl_mat_sub_alloc(hull->ctx,
1667 set->p[best]->ineq + i, 0, 1, 0, 1 + total);
1668 if (!constraints[i].c)
1670 constraints[i].ineq = 1;
1672 for (i = 0; i < min_constraints; ++i) {
1673 struct isl_hash_table_entry *entry;
1675 c_hash = isl_seq_get_hash(constraints[i].c->row[0] + 1, total);
1676 entry = isl_hash_table_find(hull->ctx, table, c_hash,
1677 max_constraint_equal, constraints[i].c->row[0] + 1, 1);
1680 isl_assert(hull->ctx, !entry->data, goto error);
1681 entry->data = &constraints[i];
1685 for (s = 0; s < set->n; ++s) {
1689 for (i = 0; i < set->p[s]->n_eq; ++i) {
1690 isl_int *eq = set->p[s]->eq[i];
1691 for (j = 0; j < 2; ++j) {
1692 isl_seq_neg(eq, eq, 1 + total);
1693 update_constraint(hull->ctx, table,
1697 for (i = 0; i < set->p[s]->n_ineq; ++i) {
1698 isl_int *ineq = set->p[s]->ineq[i];
1699 update_constraint(hull->ctx, table, ineq, total, n,
1700 set->p[s]->n_eq == 0);
1705 for (i = 0; i < min_constraints; ++i) {
1706 if (constraints[i].count < n)
1708 if (!constraints[i].ineq)
1710 j = isl_basic_set_alloc_inequality(hull);
1713 isl_seq_cpy(hull->ineq[j], constraints[i].c->row[0], 1 + total);
1716 for (s = 0; s < set->n; ++s) {
1717 if (set->p[s]->n_eq)
1719 if (set->p[s]->n_ineq != hull->n_ineq)
1721 for (i = 0; i < set->p[s]->n_ineq; ++i) {
1722 isl_int *ineq = set->p[s]->ineq[i];
1723 if (!has_constraint(hull->ctx, table, ineq, total, n))
1726 if (i == set->p[s]->n_ineq)
1730 isl_hash_table_clear(table);
1731 for (i = 0; i < min_constraints; ++i)
1732 isl_mat_free(constraints[i].c);
1737 isl_hash_table_clear(table);
1740 for (i = 0; i < min_constraints; ++i)
1741 isl_mat_free(constraints[i].c);
1746 /* Create a template for the convex hull of "set" and fill it up
1747 * obvious facet constraints, if any. If the result happens to
1748 * be the convex hull of "set" then *is_hull is set to 1.
1750 static struct isl_basic_set *proto_hull(struct isl_set *set, int *is_hull)
1752 struct isl_basic_set *hull;
1757 for (i = 0; i < set->n; ++i) {
1758 n_ineq += set->p[i]->n_eq;
1759 n_ineq += set->p[i]->n_ineq;
1761 hull = isl_basic_set_alloc_dim(isl_dim_copy(set->dim), 0, 0, n_ineq);
1762 hull = isl_basic_set_set_rational(hull);
1765 return common_constraints(hull, set, is_hull);
1768 static struct isl_basic_set *uset_convex_hull_wrap(struct isl_set *set)
1770 struct isl_basic_set *hull;
1773 hull = proto_hull(set, &is_hull);
1774 if (hull && !is_hull) {
1775 if (hull->n_ineq == 0)
1776 hull = initial_hull(hull, set);
1777 hull = extend(hull, set);
1784 /* Compute the convex hull of a set without any parameters or
1785 * integer divisions. Depending on whether the set is bounded,
1786 * we pass control to the wrapping based convex hull or
1787 * the Fourier-Motzkin elimination based convex hull.
1788 * We also handle a few special cases before checking the boundedness.
1790 static struct isl_basic_set *uset_convex_hull(struct isl_set *set)
1792 struct isl_basic_set *convex_hull = NULL;
1793 struct isl_basic_set *lin;
1795 if (isl_set_n_dim(set) == 0)
1796 return convex_hull_0d(set);
1798 set = isl_set_coalesce(set);
1799 set = isl_set_set_rational(set);
1806 convex_hull = isl_basic_set_copy(set->p[0]);
1810 if (isl_set_n_dim(set) == 1)
1811 return convex_hull_1d(set);
1813 if (isl_set_is_bounded(set))
1814 return uset_convex_hull_wrap(set);
1816 lin = uset_combined_lineality_space(isl_set_copy(set));
1819 if (isl_basic_set_is_universe(lin)) {
1823 if (lin->n_eq < isl_basic_set_total_dim(lin))
1824 return modulo_lineality(set, lin);
1825 isl_basic_set_free(lin);
1827 return uset_convex_hull_unbounded(set);
1830 isl_basic_set_free(convex_hull);
1834 /* This is the core procedure, where "set" is a "pure" set, i.e.,
1835 * without parameters or divs and where the convex hull of set is
1836 * known to be full-dimensional.
1838 static struct isl_basic_set *uset_convex_hull_wrap_bounded(struct isl_set *set)
1840 struct isl_basic_set *convex_hull = NULL;
1842 if (isl_set_n_dim(set) == 0) {
1843 convex_hull = isl_basic_set_universe(isl_dim_copy(set->dim));
1845 convex_hull = isl_basic_set_set_rational(convex_hull);
1849 set = isl_set_set_rational(set);
1853 set = isl_set_coalesce(set);
1857 convex_hull = isl_basic_set_copy(set->p[0]);
1861 if (isl_set_n_dim(set) == 1)
1862 return convex_hull_1d(set);
1864 return uset_convex_hull_wrap(set);
1870 /* Compute the convex hull of set "set" with affine hull "affine_hull",
1871 * We first remove the equalities (transforming the set), compute the
1872 * convex hull of the transformed set and then add the equalities back
1873 * (after performing the inverse transformation.
1875 static struct isl_basic_set *modulo_affine_hull(struct isl_ctx *ctx,
1876 struct isl_set *set, struct isl_basic_set *affine_hull)
1880 struct isl_basic_set *dummy;
1881 struct isl_basic_set *convex_hull;
1883 dummy = isl_basic_set_remove_equalities(
1884 isl_basic_set_copy(affine_hull), &T, &T2);
1887 isl_basic_set_free(dummy);
1888 set = isl_set_preimage(set, T);
1889 convex_hull = uset_convex_hull(set);
1890 convex_hull = isl_basic_set_preimage(convex_hull, T2);
1891 convex_hull = isl_basic_set_intersect(convex_hull, affine_hull);
1894 isl_basic_set_free(affine_hull);
1899 /* Compute the convex hull of a map.
1901 * The implementation was inspired by "Extended Convex Hull" by Fukuda et al.,
1902 * specifically, the wrapping of facets to obtain new facets.
1904 struct isl_basic_map *isl_map_convex_hull(struct isl_map *map)
1906 struct isl_basic_set *bset;
1907 struct isl_basic_map *model = NULL;
1908 struct isl_basic_set *affine_hull = NULL;
1909 struct isl_basic_map *convex_hull = NULL;
1910 struct isl_set *set = NULL;
1911 struct isl_ctx *ctx;
1918 convex_hull = isl_basic_map_empty_like_map(map);
1923 map = isl_map_detect_equalities(map);
1924 map = isl_map_align_divs(map);
1925 model = isl_basic_map_copy(map->p[0]);
1926 set = isl_map_underlying_set(map);
1930 affine_hull = isl_set_affine_hull(isl_set_copy(set));
1933 if (affine_hull->n_eq != 0)
1934 bset = modulo_affine_hull(ctx, set, affine_hull);
1936 isl_basic_set_free(affine_hull);
1937 bset = uset_convex_hull(set);
1940 convex_hull = isl_basic_map_overlying_set(bset, model);
1942 ISL_F_SET(convex_hull, ISL_BASIC_MAP_NO_IMPLICIT);
1943 ISL_F_SET(convex_hull, ISL_BASIC_MAP_ALL_EQUALITIES);
1944 ISL_F_CLR(convex_hull, ISL_BASIC_MAP_RATIONAL);
1948 isl_basic_map_free(model);
1952 struct isl_basic_set *isl_set_convex_hull(struct isl_set *set)
1954 return (struct isl_basic_set *)
1955 isl_map_convex_hull((struct isl_map *)set);
1958 struct sh_data_entry {
1959 struct isl_hash_table *table;
1960 struct isl_tab *tab;
1963 /* Holds the data needed during the simple hull computation.
1965 * n the number of basic sets in the original set
1966 * hull_table a hash table of already computed constraints
1967 * in the simple hull
1968 * p for each basic set,
1969 * table a hash table of the constraints
1970 * tab the tableau corresponding to the basic set
1973 struct isl_ctx *ctx;
1975 struct isl_hash_table *hull_table;
1976 struct sh_data_entry p[1];
1979 static void sh_data_free(struct sh_data *data)
1985 isl_hash_table_free(data->ctx, data->hull_table);
1986 for (i = 0; i < data->n; ++i) {
1987 isl_hash_table_free(data->ctx, data->p[i].table);
1988 isl_tab_free(data->p[i].tab);
1993 struct ineq_cmp_data {
1998 static int has_ineq(const void *entry, const void *val)
2000 isl_int *row = (isl_int *)entry;
2001 struct ineq_cmp_data *v = (struct ineq_cmp_data *)val;
2003 return isl_seq_eq(row + 1, v->p + 1, v->len) ||
2004 isl_seq_is_neg(row + 1, v->p + 1, v->len);
2007 static int hash_ineq(struct isl_ctx *ctx, struct isl_hash_table *table,
2008 isl_int *ineq, unsigned len)
2011 struct ineq_cmp_data v;
2012 struct isl_hash_table_entry *entry;
2016 c_hash = isl_seq_get_hash(ineq + 1, len);
2017 entry = isl_hash_table_find(ctx, table, c_hash, has_ineq, &v, 1);
2024 /* Fill hash table "table" with the constraints of "bset".
2025 * Equalities are added as two inequalities.
2026 * The value in the hash table is a pointer to the (in)equality of "bset".
2028 static int hash_basic_set(struct isl_hash_table *table,
2029 struct isl_basic_set *bset)
2032 unsigned dim = isl_basic_set_total_dim(bset);
2034 for (i = 0; i < bset->n_eq; ++i) {
2035 for (j = 0; j < 2; ++j) {
2036 isl_seq_neg(bset->eq[i], bset->eq[i], 1 + dim);
2037 if (hash_ineq(bset->ctx, table, bset->eq[i], dim) < 0)
2041 for (i = 0; i < bset->n_ineq; ++i) {
2042 if (hash_ineq(bset->ctx, table, bset->ineq[i], dim) < 0)
2048 static struct sh_data *sh_data_alloc(struct isl_set *set, unsigned n_ineq)
2050 struct sh_data *data;
2053 data = isl_calloc(set->ctx, struct sh_data,
2054 sizeof(struct sh_data) +
2055 (set->n - 1) * sizeof(struct sh_data_entry));
2058 data->ctx = set->ctx;
2060 data->hull_table = isl_hash_table_alloc(set->ctx, n_ineq);
2061 if (!data->hull_table)
2063 for (i = 0; i < set->n; ++i) {
2064 data->p[i].table = isl_hash_table_alloc(set->ctx,
2065 2 * set->p[i]->n_eq + set->p[i]->n_ineq);
2066 if (!data->p[i].table)
2068 if (hash_basic_set(data->p[i].table, set->p[i]) < 0)
2077 /* Check if inequality "ineq" is a bound for basic set "j" or if
2078 * it can be relaxed (by increasing the constant term) to become
2079 * a bound for that basic set. In the latter case, the constant
2081 * Return 1 if "ineq" is a bound
2082 * 0 if "ineq" may attain arbitrarily small values on basic set "j"
2083 * -1 if some error occurred
2085 static int is_bound(struct sh_data *data, struct isl_set *set, int j,
2088 enum isl_lp_result res;
2091 if (!data->p[j].tab) {
2092 data->p[j].tab = isl_tab_from_basic_set(set->p[j]);
2093 if (!data->p[j].tab)
2099 res = isl_tab_min(data->p[j].tab, ineq, data->ctx->one,
2101 if (res == isl_lp_ok && isl_int_is_neg(opt))
2102 isl_int_sub(ineq[0], ineq[0], opt);
2106 return res == isl_lp_ok ? 1 :
2107 res == isl_lp_unbounded ? 0 : -1;
2110 /* Check if inequality "ineq" from basic set "i" can be relaxed to
2111 * become a bound on the whole set. If so, add the (relaxed) inequality
2114 * We first check if "hull" already contains a translate of the inequality.
2115 * If so, we are done.
2116 * Then, we check if any of the previous basic sets contains a translate
2117 * of the inequality. If so, then we have already considered this
2118 * inequality and we are done.
2119 * Otherwise, for each basic set other than "i", we check if the inequality
2120 * is a bound on the basic set.
2121 * For previous basic sets, we know that they do not contain a translate
2122 * of the inequality, so we directly call is_bound.
2123 * For following basic sets, we first check if a translate of the
2124 * inequality appears in its description and if so directly update
2125 * the inequality accordingly.
2127 static struct isl_basic_set *add_bound(struct isl_basic_set *hull,
2128 struct sh_data *data, struct isl_set *set, int i, isl_int *ineq)
2131 struct ineq_cmp_data v;
2132 struct isl_hash_table_entry *entry;
2138 v.len = isl_basic_set_total_dim(hull);
2140 c_hash = isl_seq_get_hash(ineq + 1, v.len);
2142 entry = isl_hash_table_find(hull->ctx, data->hull_table, c_hash,
2147 for (j = 0; j < i; ++j) {
2148 entry = isl_hash_table_find(hull->ctx, data->p[j].table,
2149 c_hash, has_ineq, &v, 0);
2156 k = isl_basic_set_alloc_inequality(hull);
2157 isl_seq_cpy(hull->ineq[k], ineq, 1 + v.len);
2161 for (j = 0; j < i; ++j) {
2163 bound = is_bound(data, set, j, hull->ineq[k]);
2170 isl_basic_set_free_inequality(hull, 1);
2174 for (j = i + 1; j < set->n; ++j) {
2177 entry = isl_hash_table_find(hull->ctx, data->p[j].table,
2178 c_hash, has_ineq, &v, 0);
2180 ineq_j = entry->data;
2181 neg = isl_seq_is_neg(ineq_j + 1,
2182 hull->ineq[k] + 1, v.len);
2184 isl_int_neg(ineq_j[0], ineq_j[0]);
2185 if (isl_int_gt(ineq_j[0], hull->ineq[k][0]))
2186 isl_int_set(hull->ineq[k][0], ineq_j[0]);
2188 isl_int_neg(ineq_j[0], ineq_j[0]);
2191 bound = is_bound(data, set, j, hull->ineq[k]);
2198 isl_basic_set_free_inequality(hull, 1);
2202 entry = isl_hash_table_find(hull->ctx, data->hull_table, c_hash,
2206 entry->data = hull->ineq[k];
2210 isl_basic_set_free(hull);
2214 /* Check if any inequality from basic set "i" can be relaxed to
2215 * become a bound on the whole set. If so, add the (relaxed) inequality
2218 static struct isl_basic_set *add_bounds(struct isl_basic_set *bset,
2219 struct sh_data *data, struct isl_set *set, int i)
2222 unsigned dim = isl_basic_set_total_dim(bset);
2224 for (j = 0; j < set->p[i]->n_eq; ++j) {
2225 for (k = 0; k < 2; ++k) {
2226 isl_seq_neg(set->p[i]->eq[j], set->p[i]->eq[j], 1+dim);
2227 add_bound(bset, data, set, i, set->p[i]->eq[j]);
2230 for (j = 0; j < set->p[i]->n_ineq; ++j)
2231 add_bound(bset, data, set, i, set->p[i]->ineq[j]);
2235 /* Compute a superset of the convex hull of set that is described
2236 * by only translates of the constraints in the constituents of set.
2238 static struct isl_basic_set *uset_simple_hull(struct isl_set *set)
2240 struct sh_data *data = NULL;
2241 struct isl_basic_set *hull = NULL;
2249 for (i = 0; i < set->n; ++i) {
2252 n_ineq += 2 * set->p[i]->n_eq + set->p[i]->n_ineq;
2255 hull = isl_basic_set_alloc_dim(isl_dim_copy(set->dim), 0, 0, n_ineq);
2259 data = sh_data_alloc(set, n_ineq);
2263 for (i = 0; i < set->n; ++i)
2264 hull = add_bounds(hull, data, set, i);
2272 isl_basic_set_free(hull);
2277 /* Compute a superset of the convex hull of map that is described
2278 * by only translates of the constraints in the constituents of map.
2280 struct isl_basic_map *isl_map_simple_hull(struct isl_map *map)
2282 struct isl_set *set = NULL;
2283 struct isl_basic_map *model = NULL;
2284 struct isl_basic_map *hull;
2285 struct isl_basic_map *affine_hull;
2286 struct isl_basic_set *bset = NULL;
2291 hull = isl_basic_map_empty_like_map(map);
2296 hull = isl_basic_map_copy(map->p[0]);
2301 map = isl_map_detect_equalities(map);
2302 affine_hull = isl_map_affine_hull(isl_map_copy(map));
2303 map = isl_map_align_divs(map);
2304 model = isl_basic_map_copy(map->p[0]);
2306 set = isl_map_underlying_set(map);
2308 bset = uset_simple_hull(set);
2310 hull = isl_basic_map_overlying_set(bset, model);
2312 hull = isl_basic_map_intersect(hull, affine_hull);
2313 hull = isl_basic_map_convex_hull(hull);
2314 ISL_F_SET(hull, ISL_BASIC_MAP_NO_IMPLICIT);
2315 ISL_F_SET(hull, ISL_BASIC_MAP_ALL_EQUALITIES);
2320 struct isl_basic_set *isl_set_simple_hull(struct isl_set *set)
2322 return (struct isl_basic_set *)
2323 isl_map_simple_hull((struct isl_map *)set);
2326 /* Given a set "set", return parametric bounds on the dimension "dim".
2328 static struct isl_basic_set *set_bounds(struct isl_set *set, int dim)
2330 unsigned set_dim = isl_set_dim(set, isl_dim_set);
2331 set = isl_set_copy(set);
2332 set = isl_set_eliminate_dims(set, dim + 1, set_dim - (dim + 1));
2333 set = isl_set_eliminate_dims(set, 0, dim);
2334 return isl_set_convex_hull(set);
2337 /* Computes a "simple hull" and then check if each dimension in the
2338 * resulting hull is bounded by a symbolic constant. If not, the
2339 * hull is intersected with the corresponding bounds on the whole set.
2341 struct isl_basic_set *isl_set_bounded_simple_hull(struct isl_set *set)
2344 struct isl_basic_set *hull;
2345 unsigned nparam, left;
2346 int removed_divs = 0;
2348 hull = isl_set_simple_hull(isl_set_copy(set));
2352 nparam = isl_basic_set_dim(hull, isl_dim_param);
2353 for (i = 0; i < isl_basic_set_dim(hull, isl_dim_set); ++i) {
2354 int lower = 0, upper = 0;
2355 struct isl_basic_set *bounds;
2357 left = isl_basic_set_total_dim(hull) - nparam - i - 1;
2358 for (j = 0; j < hull->n_eq; ++j) {
2359 if (isl_int_is_zero(hull->eq[j][1 + nparam + i]))
2361 if (isl_seq_first_non_zero(hull->eq[j]+1+nparam+i+1,
2368 for (j = 0; j < hull->n_ineq; ++j) {
2369 if (isl_int_is_zero(hull->ineq[j][1 + nparam + i]))
2371 if (isl_seq_first_non_zero(hull->ineq[j]+1+nparam+i+1,
2373 isl_seq_first_non_zero(hull->ineq[j]+1+nparam,
2376 if (isl_int_is_pos(hull->ineq[j][1 + nparam + i]))
2387 if (!removed_divs) {
2388 set = isl_set_remove_divs(set);
2393 bounds = set_bounds(set, i);
2394 hull = isl_basic_set_intersect(hull, bounds);