2 * Copyright 2008-2009 Katholieke Universiteit Leuven
4 * Use of this software is governed by the MIT license
6 * Written by Sven Verdoolaege, K.U.Leuven, Departement
7 * Computerwetenschappen, Celestijnenlaan 200A, B-3001 Leuven, Belgium
10 #include <isl_ctx_private.h>
11 #include <isl_map_private.h>
12 #include "isl_sample.h"
13 #include "isl_sample_piplib.h"
17 #include "isl_equalities.h"
19 #include "isl_basis_reduction.h"
20 #include <isl_factorization.h>
21 #include <isl_point_private.h>
22 #include <isl_options_private.h>
24 static struct isl_vec *empty_sample(struct isl_basic_set *bset)
28 vec = isl_vec_alloc(bset->ctx, 0);
29 isl_basic_set_free(bset);
33 /* Construct a zero sample of the same dimension as bset.
34 * As a special case, if bset is zero-dimensional, this
35 * function creates a zero-dimensional sample point.
37 static struct isl_vec *zero_sample(struct isl_basic_set *bset)
40 struct isl_vec *sample;
42 dim = isl_basic_set_total_dim(bset);
43 sample = isl_vec_alloc(bset->ctx, 1 + dim);
45 isl_int_set_si(sample->el[0], 1);
46 isl_seq_clr(sample->el + 1, dim);
48 isl_basic_set_free(bset);
52 static struct isl_vec *interval_sample(struct isl_basic_set *bset)
56 struct isl_vec *sample;
58 bset = isl_basic_set_simplify(bset);
61 if (isl_basic_set_plain_is_empty(bset))
62 return empty_sample(bset);
63 if (bset->n_eq == 0 && bset->n_ineq == 0)
64 return zero_sample(bset);
66 sample = isl_vec_alloc(bset->ctx, 2);
71 isl_int_set_si(sample->block.data[0], 1);
74 isl_assert(bset->ctx, bset->n_eq == 1, goto error);
75 isl_assert(bset->ctx, bset->n_ineq == 0, goto error);
76 if (isl_int_is_one(bset->eq[0][1]))
77 isl_int_neg(sample->el[1], bset->eq[0][0]);
79 isl_assert(bset->ctx, isl_int_is_negone(bset->eq[0][1]),
81 isl_int_set(sample->el[1], bset->eq[0][0]);
83 isl_basic_set_free(bset);
88 if (isl_int_is_one(bset->ineq[0][1]))
89 isl_int_neg(sample->block.data[1], bset->ineq[0][0]);
91 isl_int_set(sample->block.data[1], bset->ineq[0][0]);
92 for (i = 1; i < bset->n_ineq; ++i) {
93 isl_seq_inner_product(sample->block.data,
94 bset->ineq[i], 2, &t);
95 if (isl_int_is_neg(t))
99 if (i < bset->n_ineq) {
100 isl_vec_free(sample);
101 return empty_sample(bset);
104 isl_basic_set_free(bset);
107 isl_basic_set_free(bset);
108 isl_vec_free(sample);
112 static struct isl_mat *independent_bounds(struct isl_basic_set *bset)
115 struct isl_mat *dirs = NULL;
116 struct isl_mat *bounds = NULL;
122 dim = isl_basic_set_n_dim(bset);
123 bounds = isl_mat_alloc(bset->ctx, 1+dim, 1+dim);
127 isl_int_set_si(bounds->row[0][0], 1);
128 isl_seq_clr(bounds->row[0]+1, dim);
131 if (bset->n_ineq == 0)
134 dirs = isl_mat_alloc(bset->ctx, dim, dim);
136 isl_mat_free(bounds);
139 isl_seq_cpy(dirs->row[0], bset->ineq[0]+1, dirs->n_col);
140 isl_seq_cpy(bounds->row[1], bset->ineq[0], bounds->n_col);
141 for (j = 1, n = 1; n < dim && j < bset->n_ineq; ++j) {
144 isl_seq_cpy(dirs->row[n], bset->ineq[j]+1, dirs->n_col);
146 pos = isl_seq_first_non_zero(dirs->row[n], dirs->n_col);
149 for (i = 0; i < n; ++i) {
151 pos_i = isl_seq_first_non_zero(dirs->row[i], dirs->n_col);
156 isl_seq_elim(dirs->row[n], dirs->row[i], pos,
158 pos = isl_seq_first_non_zero(dirs->row[n], dirs->n_col);
166 isl_int *t = dirs->row[n];
167 for (k = n; k > i; --k)
168 dirs->row[k] = dirs->row[k-1];
172 isl_seq_cpy(bounds->row[n], bset->ineq[j], bounds->n_col);
179 static void swap_inequality(struct isl_basic_set *bset, int a, int b)
181 isl_int *t = bset->ineq[a];
182 bset->ineq[a] = bset->ineq[b];
186 /* Skew into positive orthant and project out lineality space.
188 * We perform a unimodular transformation that turns a selected
189 * maximal set of linearly independent bounds into constraints
190 * on the first dimensions that impose that these first dimensions
191 * are non-negative. In particular, the constraint matrix is lower
192 * triangular with positive entries on the diagonal and negative
194 * If "bset" has a lineality space then these constraints (and therefore
195 * all constraints in bset) only involve the first dimensions.
196 * The remaining dimensions then do not appear in any constraints and
197 * we can select any value for them, say zero. We therefore project
198 * out this final dimensions and plug in the value zero later. This
199 * is accomplished by simply dropping the final columns of
200 * the unimodular transformation.
202 static struct isl_basic_set *isl_basic_set_skew_to_positive_orthant(
203 struct isl_basic_set *bset, struct isl_mat **T)
205 struct isl_mat *U = NULL;
206 struct isl_mat *bounds = NULL;
208 unsigned old_dim, new_dim;
214 isl_assert(bset->ctx, isl_basic_set_n_param(bset) == 0, goto error);
215 isl_assert(bset->ctx, bset->n_div == 0, goto error);
216 isl_assert(bset->ctx, bset->n_eq == 0, goto error);
218 old_dim = isl_basic_set_n_dim(bset);
219 /* Try to move (multiples of) unit rows up. */
220 for (i = 0, j = 0; i < bset->n_ineq; ++i) {
221 int pos = isl_seq_first_non_zero(bset->ineq[i]+1, old_dim);
224 if (isl_seq_first_non_zero(bset->ineq[i]+1+pos+1,
228 swap_inequality(bset, i, j);
231 bounds = independent_bounds(bset);
234 new_dim = bounds->n_row - 1;
235 bounds = isl_mat_left_hermite(bounds, 1, &U, NULL);
238 U = isl_mat_drop_cols(U, 1 + new_dim, old_dim - new_dim);
239 bset = isl_basic_set_preimage(bset, isl_mat_copy(U));
243 isl_mat_free(bounds);
246 isl_mat_free(bounds);
248 isl_basic_set_free(bset);
252 /* Find a sample integer point, if any, in bset, which is known
253 * to have equalities. If bset contains no integer points, then
254 * return a zero-length vector.
255 * We simply remove the known equalities, compute a sample
256 * in the resulting bset, using the specified recurse function,
257 * and then transform the sample back to the original space.
259 static struct isl_vec *sample_eq(struct isl_basic_set *bset,
260 struct isl_vec *(*recurse)(struct isl_basic_set *))
263 struct isl_vec *sample;
268 bset = isl_basic_set_remove_equalities(bset, &T, NULL);
269 sample = recurse(bset);
270 if (!sample || sample->size == 0)
273 sample = isl_mat_vec_product(T, sample);
277 /* Return a matrix containing the equalities of the tableau
278 * in constraint form. The tableau is assumed to have
279 * an associated bset that has been kept up-to-date.
281 static struct isl_mat *tab_equalities(struct isl_tab *tab)
286 struct isl_basic_set *bset;
291 bset = isl_tab_peek_bset(tab);
292 isl_assert(tab->mat->ctx, bset, return NULL);
294 n_eq = tab->n_var - tab->n_col + tab->n_dead;
295 if (tab->empty || n_eq == 0)
296 return isl_mat_alloc(tab->mat->ctx, 0, tab->n_var);
297 if (n_eq == tab->n_var)
298 return isl_mat_identity(tab->mat->ctx, tab->n_var);
300 eq = isl_mat_alloc(tab->mat->ctx, n_eq, tab->n_var);
303 for (i = 0, j = 0; i < tab->n_con; ++i) {
304 if (tab->con[i].is_row)
306 if (tab->con[i].index >= 0 && tab->con[i].index >= tab->n_dead)
309 isl_seq_cpy(eq->row[j], bset->eq[i] + 1, tab->n_var);
311 isl_seq_cpy(eq->row[j],
312 bset->ineq[i - bset->n_eq] + 1, tab->n_var);
315 isl_assert(bset->ctx, j == n_eq, goto error);
322 /* Compute and return an initial basis for the bounded tableau "tab".
324 * If the tableau is either full-dimensional or zero-dimensional,
325 * the we simply return an identity matrix.
326 * Otherwise, we construct a basis whose first directions correspond
329 static struct isl_mat *initial_basis(struct isl_tab *tab)
335 tab->n_unbounded = 0;
336 tab->n_zero = n_eq = tab->n_var - tab->n_col + tab->n_dead;
337 if (tab->empty || n_eq == 0 || n_eq == tab->n_var)
338 return isl_mat_identity(tab->mat->ctx, 1 + tab->n_var);
340 eq = tab_equalities(tab);
341 eq = isl_mat_left_hermite(eq, 0, NULL, &Q);
346 Q = isl_mat_lin_to_aff(Q);
350 /* Compute the minimum of the current ("level") basis row over "tab"
351 * and store the result in position "level" of "min".
353 static enum isl_lp_result compute_min(isl_ctx *ctx, struct isl_tab *tab,
354 __isl_keep isl_vec *min, int level)
356 return isl_tab_min(tab, tab->basis->row[1 + level],
357 ctx->one, &min->el[level], NULL, 0);
360 /* Compute the maximum of the current ("level") basis row over "tab"
361 * and store the result in position "level" of "max".
363 static enum isl_lp_result compute_max(isl_ctx *ctx, struct isl_tab *tab,
364 __isl_keep isl_vec *max, int level)
366 enum isl_lp_result res;
367 unsigned dim = tab->n_var;
369 isl_seq_neg(tab->basis->row[1 + level] + 1,
370 tab->basis->row[1 + level] + 1, dim);
371 res = isl_tab_min(tab, tab->basis->row[1 + level],
372 ctx->one, &max->el[level], NULL, 0);
373 isl_seq_neg(tab->basis->row[1 + level] + 1,
374 tab->basis->row[1 + level] + 1, dim);
375 isl_int_neg(max->el[level], max->el[level]);
380 /* Given a tableau representing a set, find and return
381 * an integer point in the set, if there is any.
383 * We perform a depth first search
384 * for an integer point, by scanning all possible values in the range
385 * attained by a basis vector, where an initial basis may have been set
386 * by the calling function. Otherwise an initial basis that exploits
387 * the equalities in the tableau is created.
388 * tab->n_zero is currently ignored and is clobbered by this function.
390 * The tableau is allowed to have unbounded direction, but then
391 * the calling function needs to set an initial basis, with the
392 * unbounded directions last and with tab->n_unbounded set
393 * to the number of unbounded directions.
394 * Furthermore, the calling functions needs to add shifted copies
395 * of all constraints involving unbounded directions to ensure
396 * that any feasible rational value in these directions can be rounded
397 * up to yield a feasible integer value.
398 * In particular, let B define the given basis x' = B x
399 * and let T be the inverse of B, i.e., X = T x'.
400 * Let a x + c >= 0 be a constraint of the set represented by the tableau,
401 * or a T x' + c >= 0 in terms of the given basis. Assume that
402 * the bounded directions have an integer value, then we can safely
403 * round up the values for the unbounded directions if we make sure
404 * that x' not only satisfies the original constraint, but also
405 * the constraint "a T x' + c + s >= 0" with s the sum of all
406 * negative values in the last n_unbounded entries of "a T".
407 * The calling function therefore needs to add the constraint
408 * a x + c + s >= 0. The current function then scans the first
409 * directions for an integer value and once those have been found,
410 * it can compute "T ceil(B x)" to yield an integer point in the set.
411 * Note that during the search, the first rows of B may be changed
412 * by a basis reduction, but the last n_unbounded rows of B remain
413 * unaltered and are also not mixed into the first rows.
415 * The search is implemented iteratively. "level" identifies the current
416 * basis vector. "init" is true if we want the first value at the current
417 * level and false if we want the next value.
419 * The initial basis is the identity matrix. If the range in some direction
420 * contains more than one integer value, we perform basis reduction based
421 * on the value of ctx->opt->gbr
422 * - ISL_GBR_NEVER: never perform basis reduction
423 * - ISL_GBR_ONCE: only perform basis reduction the first
424 * time such a range is encountered
425 * - ISL_GBR_ALWAYS: always perform basis reduction when
426 * such a range is encountered
428 * When ctx->opt->gbr is set to ISL_GBR_ALWAYS, then we allow the basis
429 * reduction computation to return early. That is, as soon as it
430 * finds a reasonable first direction.
432 struct isl_vec *isl_tab_sample(struct isl_tab *tab)
437 struct isl_vec *sample;
440 enum isl_lp_result res;
444 struct isl_tab_undo **snap;
449 return isl_vec_alloc(tab->mat->ctx, 0);
452 tab->basis = initial_basis(tab);
455 isl_assert(tab->mat->ctx, tab->basis->n_row == tab->n_var + 1,
457 isl_assert(tab->mat->ctx, tab->basis->n_col == tab->n_var + 1,
464 if (tab->n_unbounded == tab->n_var) {
465 sample = isl_tab_get_sample_value(tab);
466 sample = isl_mat_vec_product(isl_mat_copy(tab->basis), sample);
467 sample = isl_vec_ceil(sample);
468 sample = isl_mat_vec_inverse_product(isl_mat_copy(tab->basis),
473 if (isl_tab_extend_cons(tab, dim + 1) < 0)
476 min = isl_vec_alloc(ctx, dim);
477 max = isl_vec_alloc(ctx, dim);
478 snap = isl_alloc_array(ctx, struct isl_tab_undo *, dim);
480 if (!min || !max || !snap)
489 res = compute_min(ctx, tab, min, level);
490 if (res == isl_lp_error)
492 if (res != isl_lp_ok)
493 isl_die(ctx, isl_error_internal,
494 "expecting bounded rational solution",
496 if (isl_tab_sample_is_integer(tab))
498 res = compute_max(ctx, tab, max, level);
499 if (res == isl_lp_error)
501 if (res != isl_lp_ok)
502 isl_die(ctx, isl_error_internal,
503 "expecting bounded rational solution",
505 if (isl_tab_sample_is_integer(tab))
507 if (!reduced && ctx->opt->gbr != ISL_GBR_NEVER &&
508 isl_int_lt(min->el[level], max->el[level])) {
509 unsigned gbr_only_first;
510 if (ctx->opt->gbr == ISL_GBR_ONCE)
511 ctx->opt->gbr = ISL_GBR_NEVER;
513 gbr_only_first = ctx->opt->gbr_only_first;
514 ctx->opt->gbr_only_first =
515 ctx->opt->gbr == ISL_GBR_ALWAYS;
516 tab = isl_tab_compute_reduced_basis(tab);
517 ctx->opt->gbr_only_first = gbr_only_first;
518 if (!tab || !tab->basis)
524 snap[level] = isl_tab_snap(tab);
526 isl_int_add_ui(min->el[level], min->el[level], 1);
528 if (isl_int_gt(min->el[level], max->el[level])) {
532 if (isl_tab_rollback(tab, snap[level]) < 0)
536 isl_int_neg(tab->basis->row[1 + level][0], min->el[level]);
537 if (isl_tab_add_valid_eq(tab, tab->basis->row[1 + level]) < 0)
539 isl_int_set_si(tab->basis->row[1 + level][0], 0);
540 if (level + tab->n_unbounded < dim - 1) {
549 sample = isl_tab_get_sample_value(tab);
552 if (tab->n_unbounded && !isl_int_is_one(sample->el[0])) {
553 sample = isl_mat_vec_product(isl_mat_copy(tab->basis),
555 sample = isl_vec_ceil(sample);
556 sample = isl_mat_vec_inverse_product(
557 isl_mat_copy(tab->basis), sample);
560 sample = isl_vec_alloc(ctx, 0);
575 static struct isl_vec *sample_bounded(struct isl_basic_set *bset);
577 /* Compute a sample point of the given basic set, based on the given,
578 * non-trivial factorization.
580 static __isl_give isl_vec *factored_sample(__isl_take isl_basic_set *bset,
581 __isl_take isl_factorizer *f)
584 isl_vec *sample = NULL;
589 ctx = isl_basic_set_get_ctx(bset);
593 nparam = isl_basic_set_dim(bset, isl_dim_param);
594 nvar = isl_basic_set_dim(bset, isl_dim_set);
596 sample = isl_vec_alloc(ctx, 1 + isl_basic_set_total_dim(bset));
599 isl_int_set_si(sample->el[0], 1);
601 bset = isl_morph_basic_set(isl_morph_copy(f->morph), bset);
603 for (i = 0, n = 0; i < f->n_group; ++i) {
604 isl_basic_set *bset_i;
607 bset_i = isl_basic_set_copy(bset);
608 bset_i = isl_basic_set_drop_constraints_involving(bset_i,
609 nparam + n + f->len[i], nvar - n - f->len[i]);
610 bset_i = isl_basic_set_drop_constraints_involving(bset_i,
612 bset_i = isl_basic_set_drop(bset_i, isl_dim_set,
613 n + f->len[i], nvar - n - f->len[i]);
614 bset_i = isl_basic_set_drop(bset_i, isl_dim_set, 0, n);
616 sample_i = sample_bounded(bset_i);
619 if (sample_i->size == 0) {
620 isl_basic_set_free(bset);
621 isl_factorizer_free(f);
622 isl_vec_free(sample);
625 isl_seq_cpy(sample->el + 1 + nparam + n,
626 sample_i->el + 1, f->len[i]);
627 isl_vec_free(sample_i);
632 f->morph = isl_morph_inverse(f->morph);
633 sample = isl_morph_vec(isl_morph_copy(f->morph), sample);
635 isl_basic_set_free(bset);
636 isl_factorizer_free(f);
639 isl_basic_set_free(bset);
640 isl_factorizer_free(f);
641 isl_vec_free(sample);
645 /* Given a basic set that is known to be bounded, find and return
646 * an integer point in the basic set, if there is any.
648 * After handling some trivial cases, we construct a tableau
649 * and then use isl_tab_sample to find a sample, passing it
650 * the identity matrix as initial basis.
652 static struct isl_vec *sample_bounded(struct isl_basic_set *bset)
656 struct isl_vec *sample;
657 struct isl_tab *tab = NULL;
663 if (isl_basic_set_plain_is_empty(bset))
664 return empty_sample(bset);
666 dim = isl_basic_set_total_dim(bset);
668 return zero_sample(bset);
670 return interval_sample(bset);
672 return sample_eq(bset, sample_bounded);
674 f = isl_basic_set_factorizer(bset);
678 return factored_sample(bset, f);
679 isl_factorizer_free(f);
683 tab = isl_tab_from_basic_set(bset, 1);
684 if (tab && tab->empty) {
686 ISL_F_SET(bset, ISL_BASIC_SET_EMPTY);
687 sample = isl_vec_alloc(bset->ctx, 0);
688 isl_basic_set_free(bset);
692 if (!ISL_F_ISSET(bset, ISL_BASIC_SET_NO_IMPLICIT))
693 if (isl_tab_detect_implicit_equalities(tab) < 0)
696 sample = isl_tab_sample(tab);
700 if (sample->size > 0) {
701 isl_vec_free(bset->sample);
702 bset->sample = isl_vec_copy(sample);
705 isl_basic_set_free(bset);
709 isl_basic_set_free(bset);
714 /* Given a basic set "bset" and a value "sample" for the first coordinates
715 * of bset, plug in these values and drop the corresponding coordinates.
717 * We do this by computing the preimage of the transformation
723 * where [1 s] is the sample value and I is the identity matrix of the
724 * appropriate dimension.
726 static struct isl_basic_set *plug_in(struct isl_basic_set *bset,
727 struct isl_vec *sample)
733 if (!bset || !sample)
736 total = isl_basic_set_total_dim(bset);
737 T = isl_mat_alloc(bset->ctx, 1 + total, 1 + total - (sample->size - 1));
741 for (i = 0; i < sample->size; ++i) {
742 isl_int_set(T->row[i][0], sample->el[i]);
743 isl_seq_clr(T->row[i] + 1, T->n_col - 1);
745 for (i = 0; i < T->n_col - 1; ++i) {
746 isl_seq_clr(T->row[sample->size + i], T->n_col);
747 isl_int_set_si(T->row[sample->size + i][1 + i], 1);
749 isl_vec_free(sample);
751 bset = isl_basic_set_preimage(bset, T);
754 isl_basic_set_free(bset);
755 isl_vec_free(sample);
759 /* Given a basic set "bset", return any (possibly non-integer) point
762 static struct isl_vec *rational_sample(struct isl_basic_set *bset)
765 struct isl_vec *sample;
770 tab = isl_tab_from_basic_set(bset, 0);
771 sample = isl_tab_get_sample_value(tab);
774 isl_basic_set_free(bset);
779 /* Given a linear cone "cone" and a rational point "vec",
780 * construct a polyhedron with shifted copies of the constraints in "cone",
781 * i.e., a polyhedron with "cone" as its recession cone, such that each
782 * point x in this polyhedron is such that the unit box positioned at x
783 * lies entirely inside the affine cone 'vec + cone'.
784 * Any rational point in this polyhedron may therefore be rounded up
785 * to yield an integer point that lies inside said affine cone.
787 * Denote the constraints of cone by "<a_i, x> >= 0" and the rational
788 * point "vec" by v/d.
789 * Let b_i = <a_i, v>. Then the affine cone 'vec + cone' is given
790 * by <a_i, x> - b/d >= 0.
791 * The polyhedron <a_i, x> - ceil{b/d} >= 0 is a subset of this affine cone.
792 * We prefer this polyhedron over the actual affine cone because it doesn't
793 * require a scaling of the constraints.
794 * If each of the vertices of the unit cube positioned at x lies inside
795 * this polyhedron, then the whole unit cube at x lies inside the affine cone.
796 * We therefore impose that x' = x + \sum e_i, for any selection of unit
797 * vectors lies inside the polyhedron, i.e.,
799 * <a_i, x'> - ceil{b/d} = <a_i, x> + sum a_i - ceil{b/d} >= 0
801 * The most stringent of these constraints is the one that selects
802 * all negative a_i, so the polyhedron we are looking for has constraints
804 * <a_i, x> + sum_{a_i < 0} a_i - ceil{b/d} >= 0
806 * Note that if cone were known to have only non-negative rays
807 * (which can be accomplished by a unimodular transformation),
808 * then we would only have to check the points x' = x + e_i
809 * and we only have to add the smallest negative a_i (if any)
810 * instead of the sum of all negative a_i.
812 static struct isl_basic_set *shift_cone(struct isl_basic_set *cone,
818 struct isl_basic_set *shift = NULL;
823 isl_assert(cone->ctx, cone->n_eq == 0, goto error);
825 total = isl_basic_set_total_dim(cone);
827 shift = isl_basic_set_alloc_space(isl_basic_set_get_space(cone),
830 for (i = 0; i < cone->n_ineq; ++i) {
831 k = isl_basic_set_alloc_inequality(shift);
834 isl_seq_cpy(shift->ineq[k] + 1, cone->ineq[i] + 1, total);
835 isl_seq_inner_product(shift->ineq[k] + 1, vec->el + 1, total,
837 isl_int_cdiv_q(shift->ineq[k][0],
838 shift->ineq[k][0], vec->el[0]);
839 isl_int_neg(shift->ineq[k][0], shift->ineq[k][0]);
840 for (j = 0; j < total; ++j) {
841 if (isl_int_is_nonneg(shift->ineq[k][1 + j]))
843 isl_int_add(shift->ineq[k][0],
844 shift->ineq[k][0], shift->ineq[k][1 + j]);
848 isl_basic_set_free(cone);
851 return isl_basic_set_finalize(shift);
853 isl_basic_set_free(shift);
854 isl_basic_set_free(cone);
859 /* Given a rational point vec in a (transformed) basic set,
860 * such that cone is the recession cone of the original basic set,
861 * "round up" the rational point to an integer point.
863 * We first check if the rational point just happens to be integer.
864 * If not, we transform the cone in the same way as the basic set,
865 * pick a point x in this cone shifted to the rational point such that
866 * the whole unit cube at x is also inside this affine cone.
867 * Then we simply round up the coordinates of x and return the
868 * resulting integer point.
870 static struct isl_vec *round_up_in_cone(struct isl_vec *vec,
871 struct isl_basic_set *cone, struct isl_mat *U)
875 if (!vec || !cone || !U)
878 isl_assert(vec->ctx, vec->size != 0, goto error);
879 if (isl_int_is_one(vec->el[0])) {
881 isl_basic_set_free(cone);
885 total = isl_basic_set_total_dim(cone);
886 cone = isl_basic_set_preimage(cone, U);
887 cone = isl_basic_set_remove_dims(cone, isl_dim_set,
888 0, total - (vec->size - 1));
890 cone = shift_cone(cone, vec);
892 vec = rational_sample(cone);
893 vec = isl_vec_ceil(vec);
898 isl_basic_set_free(cone);
902 /* Concatenate two integer vectors, i.e., two vectors with denominator
903 * (stored in element 0) equal to 1.
905 static struct isl_vec *vec_concat(struct isl_vec *vec1, struct isl_vec *vec2)
911 isl_assert(vec1->ctx, vec1->size > 0, goto error);
912 isl_assert(vec2->ctx, vec2->size > 0, goto error);
913 isl_assert(vec1->ctx, isl_int_is_one(vec1->el[0]), goto error);
914 isl_assert(vec2->ctx, isl_int_is_one(vec2->el[0]), goto error);
916 vec = isl_vec_alloc(vec1->ctx, vec1->size + vec2->size - 1);
920 isl_seq_cpy(vec->el, vec1->el, vec1->size);
921 isl_seq_cpy(vec->el + vec1->size, vec2->el + 1, vec2->size - 1);
933 /* Give a basic set "bset" with recession cone "cone", compute and
934 * return an integer point in bset, if any.
936 * If the recession cone is full-dimensional, then we know that
937 * bset contains an infinite number of integer points and it is
938 * fairly easy to pick one of them.
939 * If the recession cone is not full-dimensional, then we first
940 * transform bset such that the bounded directions appear as
941 * the first dimensions of the transformed basic set.
942 * We do this by using a unimodular transformation that transforms
943 * the equalities in the recession cone to equalities on the first
946 * The transformed set is then projected onto its bounded dimensions.
947 * Note that to compute this projection, we can simply drop all constraints
948 * involving any of the unbounded dimensions since these constraints
949 * cannot be combined to produce a constraint on the bounded dimensions.
950 * To see this, assume that there is such a combination of constraints
951 * that produces a constraint on the bounded dimensions. This means
952 * that some combination of the unbounded dimensions has both an upper
953 * bound and a lower bound in terms of the bounded dimensions, but then
954 * this combination would be a bounded direction too and would have been
955 * transformed into a bounded dimensions.
957 * We then compute a sample value in the bounded dimensions.
958 * If no such value can be found, then the original set did not contain
959 * any integer points and we are done.
960 * Otherwise, we plug in the value we found in the bounded dimensions,
961 * project out these bounded dimensions and end up with a set with
962 * a full-dimensional recession cone.
963 * A sample point in this set is computed by "rounding up" any
964 * rational point in the set.
966 * The sample points in the bounded and unbounded dimensions are
967 * then combined into a single sample point and transformed back
968 * to the original space.
970 __isl_give isl_vec *isl_basic_set_sample_with_cone(
971 __isl_take isl_basic_set *bset, __isl_take isl_basic_set *cone)
975 struct isl_mat *M, *U;
976 struct isl_vec *sample;
977 struct isl_vec *cone_sample;
979 struct isl_basic_set *bounded;
985 total = isl_basic_set_total_dim(cone);
986 cone_dim = total - cone->n_eq;
988 M = isl_mat_sub_alloc6(bset->ctx, cone->eq, 0, cone->n_eq, 1, total);
989 M = isl_mat_left_hermite(M, 0, &U, NULL);
994 U = isl_mat_lin_to_aff(U);
995 bset = isl_basic_set_preimage(bset, isl_mat_copy(U));
997 bounded = isl_basic_set_copy(bset);
998 bounded = isl_basic_set_drop_constraints_involving(bounded,
999 total - cone_dim, cone_dim);
1000 bounded = isl_basic_set_drop_dims(bounded, total - cone_dim, cone_dim);
1001 sample = sample_bounded(bounded);
1002 if (!sample || sample->size == 0) {
1003 isl_basic_set_free(bset);
1004 isl_basic_set_free(cone);
1008 bset = plug_in(bset, isl_vec_copy(sample));
1009 cone_sample = rational_sample(bset);
1010 cone_sample = round_up_in_cone(cone_sample, cone, isl_mat_copy(U));
1011 sample = vec_concat(sample, cone_sample);
1012 sample = isl_mat_vec_product(U, sample);
1015 isl_basic_set_free(cone);
1016 isl_basic_set_free(bset);
1020 static void vec_sum_of_neg(struct isl_vec *v, isl_int *s)
1024 isl_int_set_si(*s, 0);
1026 for (i = 0; i < v->size; ++i)
1027 if (isl_int_is_neg(v->el[i]))
1028 isl_int_add(*s, *s, v->el[i]);
1031 /* Given a tableau "tab", a tableau "tab_cone" that corresponds
1032 * to the recession cone and the inverse of a new basis U = inv(B),
1033 * with the unbounded directions in B last,
1034 * add constraints to "tab" that ensure any rational value
1035 * in the unbounded directions can be rounded up to an integer value.
1037 * The new basis is given by x' = B x, i.e., x = U x'.
1038 * For any rational value of the last tab->n_unbounded coordinates
1039 * in the update tableau, the value that is obtained by rounding
1040 * up this value should be contained in the original tableau.
1041 * For any constraint "a x + c >= 0", we therefore need to add
1042 * a constraint "a x + c + s >= 0", with s the sum of all negative
1043 * entries in the last elements of "a U".
1045 * Since we are not interested in the first entries of any of the "a U",
1046 * we first drop the columns of U that correpond to bounded directions.
1048 static int tab_shift_cone(struct isl_tab *tab,
1049 struct isl_tab *tab_cone, struct isl_mat *U)
1053 struct isl_basic_set *bset = NULL;
1055 if (tab && tab->n_unbounded == 0) {
1060 if (!tab || !tab_cone || !U)
1062 bset = isl_tab_peek_bset(tab_cone);
1063 U = isl_mat_drop_cols(U, 0, tab->n_var - tab->n_unbounded);
1064 for (i = 0; i < bset->n_ineq; ++i) {
1066 struct isl_vec *row = NULL;
1067 if (isl_tab_is_equality(tab_cone, tab_cone->n_eq + i))
1069 row = isl_vec_alloc(bset->ctx, tab_cone->n_var);
1072 isl_seq_cpy(row->el, bset->ineq[i] + 1, tab_cone->n_var);
1073 row = isl_vec_mat_product(row, isl_mat_copy(U));
1076 vec_sum_of_neg(row, &v);
1078 if (isl_int_is_zero(v))
1080 tab = isl_tab_extend(tab, 1);
1081 isl_int_add(bset->ineq[i][0], bset->ineq[i][0], v);
1082 ok = isl_tab_add_ineq(tab, bset->ineq[i]) >= 0;
1083 isl_int_sub(bset->ineq[i][0], bset->ineq[i][0], v);
1097 /* Compute and return an initial basis for the possibly
1098 * unbounded tableau "tab". "tab_cone" is a tableau
1099 * for the corresponding recession cone.
1100 * Additionally, add constraints to "tab" that ensure
1101 * that any rational value for the unbounded directions
1102 * can be rounded up to an integer value.
1104 * If the tableau is bounded, i.e., if the recession cone
1105 * is zero-dimensional, then we just use inital_basis.
1106 * Otherwise, we construct a basis whose first directions
1107 * correspond to equalities, followed by bounded directions,
1108 * i.e., equalities in the recession cone.
1109 * The remaining directions are then unbounded.
1111 int isl_tab_set_initial_basis_with_cone(struct isl_tab *tab,
1112 struct isl_tab *tab_cone)
1115 struct isl_mat *cone_eq;
1116 struct isl_mat *U, *Q;
1118 if (!tab || !tab_cone)
1121 if (tab_cone->n_col == tab_cone->n_dead) {
1122 tab->basis = initial_basis(tab);
1123 return tab->basis ? 0 : -1;
1126 eq = tab_equalities(tab);
1129 tab->n_zero = eq->n_row;
1130 cone_eq = tab_equalities(tab_cone);
1131 eq = isl_mat_concat(eq, cone_eq);
1134 tab->n_unbounded = tab->n_var - (eq->n_row - tab->n_zero);
1135 eq = isl_mat_left_hermite(eq, 0, &U, &Q);
1139 tab->basis = isl_mat_lin_to_aff(Q);
1140 if (tab_shift_cone(tab, tab_cone, U) < 0)
1147 /* Compute and return a sample point in bset using generalized basis
1148 * reduction. We first check if the input set has a non-trivial
1149 * recession cone. If so, we perform some extra preprocessing in
1150 * sample_with_cone. Otherwise, we directly perform generalized basis
1153 static struct isl_vec *gbr_sample(struct isl_basic_set *bset)
1156 struct isl_basic_set *cone;
1158 dim = isl_basic_set_total_dim(bset);
1160 cone = isl_basic_set_recession_cone(isl_basic_set_copy(bset));
1164 if (cone->n_eq < dim)
1165 return isl_basic_set_sample_with_cone(bset, cone);
1167 isl_basic_set_free(cone);
1168 return sample_bounded(bset);
1170 isl_basic_set_free(bset);
1174 static struct isl_vec *pip_sample(struct isl_basic_set *bset)
1177 struct isl_ctx *ctx;
1178 struct isl_vec *sample;
1180 bset = isl_basic_set_skew_to_positive_orthant(bset, &T);
1185 sample = isl_pip_basic_set_sample(bset);
1187 if (sample && sample->size != 0)
1188 sample = isl_mat_vec_product(T, sample);
1195 static struct isl_vec *basic_set_sample(struct isl_basic_set *bset, int bounded)
1197 struct isl_ctx *ctx;
1203 if (isl_basic_set_plain_is_empty(bset))
1204 return empty_sample(bset);
1206 dim = isl_basic_set_n_dim(bset);
1207 isl_assert(ctx, isl_basic_set_n_param(bset) == 0, goto error);
1208 isl_assert(ctx, bset->n_div == 0, goto error);
1210 if (bset->sample && bset->sample->size == 1 + dim) {
1211 int contains = isl_basic_set_contains(bset, bset->sample);
1215 struct isl_vec *sample = isl_vec_copy(bset->sample);
1216 isl_basic_set_free(bset);
1220 isl_vec_free(bset->sample);
1221 bset->sample = NULL;
1224 return sample_eq(bset, bounded ? isl_basic_set_sample_bounded
1225 : isl_basic_set_sample_vec);
1227 return zero_sample(bset);
1229 return interval_sample(bset);
1231 switch (bset->ctx->opt->ilp_solver) {
1233 return pip_sample(bset);
1235 return bounded ? sample_bounded(bset) : gbr_sample(bset);
1237 isl_assert(bset->ctx, 0, );
1239 isl_basic_set_free(bset);
1243 __isl_give isl_vec *isl_basic_set_sample_vec(__isl_take isl_basic_set *bset)
1245 return basic_set_sample(bset, 0);
1248 /* Compute an integer sample in "bset", where the caller guarantees
1249 * that "bset" is bounded.
1251 struct isl_vec *isl_basic_set_sample_bounded(struct isl_basic_set *bset)
1253 return basic_set_sample(bset, 1);
1256 __isl_give isl_basic_set *isl_basic_set_from_vec(__isl_take isl_vec *vec)
1260 struct isl_basic_set *bset = NULL;
1261 struct isl_ctx *ctx;
1267 isl_assert(ctx, vec->size != 0, goto error);
1269 bset = isl_basic_set_alloc(ctx, 0, vec->size - 1, 0, vec->size - 1, 0);
1272 dim = isl_basic_set_n_dim(bset);
1273 for (i = dim - 1; i >= 0; --i) {
1274 k = isl_basic_set_alloc_equality(bset);
1277 isl_seq_clr(bset->eq[k], 1 + dim);
1278 isl_int_neg(bset->eq[k][0], vec->el[1 + i]);
1279 isl_int_set(bset->eq[k][1 + i], vec->el[0]);
1285 isl_basic_set_free(bset);
1290 __isl_give isl_basic_map *isl_basic_map_sample(__isl_take isl_basic_map *bmap)
1292 struct isl_basic_set *bset;
1293 struct isl_vec *sample_vec;
1295 bset = isl_basic_map_underlying_set(isl_basic_map_copy(bmap));
1296 sample_vec = isl_basic_set_sample_vec(bset);
1299 if (sample_vec->size == 0) {
1300 struct isl_basic_map *sample;
1301 sample = isl_basic_map_empty_like(bmap);
1302 isl_vec_free(sample_vec);
1303 isl_basic_map_free(bmap);
1306 bset = isl_basic_set_from_vec(sample_vec);
1307 return isl_basic_map_overlying_set(bset, bmap);
1309 isl_basic_map_free(bmap);
1313 __isl_give isl_basic_set *isl_basic_set_sample(__isl_take isl_basic_set *bset)
1315 return isl_basic_map_sample(bset);
1318 __isl_give isl_basic_map *isl_map_sample(__isl_take isl_map *map)
1321 isl_basic_map *sample = NULL;
1326 for (i = 0; i < map->n; ++i) {
1327 sample = isl_basic_map_sample(isl_basic_map_copy(map->p[i]));
1330 if (!ISL_F_ISSET(sample, ISL_BASIC_MAP_EMPTY))
1332 isl_basic_map_free(sample);
1335 sample = isl_basic_map_empty_like_map(map);
1343 __isl_give isl_basic_set *isl_set_sample(__isl_take isl_set *set)
1345 return (isl_basic_set *) isl_map_sample((isl_map *)set);
1348 __isl_give isl_point *isl_basic_set_sample_point(__isl_take isl_basic_set *bset)
1353 dim = isl_basic_set_get_space(bset);
1354 bset = isl_basic_set_underlying_set(bset);
1355 vec = isl_basic_set_sample_vec(bset);
1357 return isl_point_alloc(dim, vec);
1360 __isl_give isl_point *isl_set_sample_point(__isl_take isl_set *set)
1368 for (i = 0; i < set->n; ++i) {
1369 pnt = isl_basic_set_sample_point(isl_basic_set_copy(set->p[i]));
1372 if (!isl_point_is_void(pnt))
1374 isl_point_free(pnt);
1377 pnt = isl_point_void(isl_set_get_space(set));