2 #include "isl_map_private.h"
6 * The implementation of tableaus in this file was inspired by Section 8
7 * of David Detlefs, Greg Nelson and James B. Saxe, "Simplify: a theorem
8 * prover for program checking".
11 struct isl_tab *isl_tab_alloc(struct isl_ctx *ctx,
12 unsigned n_row, unsigned n_var, unsigned M)
18 tab = isl_calloc_type(ctx, struct isl_tab);
21 tab->mat = isl_mat_alloc(ctx, n_row, off + n_var);
24 tab->var = isl_alloc_array(ctx, struct isl_tab_var, n_var);
27 tab->con = isl_alloc_array(ctx, struct isl_tab_var, n_row);
30 tab->col_var = isl_alloc_array(ctx, int, n_var);
33 tab->row_var = isl_alloc_array(ctx, int, n_row);
36 for (i = 0; i < n_var; ++i) {
37 tab->var[i].index = i;
38 tab->var[i].is_row = 0;
39 tab->var[i].is_nonneg = 0;
40 tab->var[i].is_zero = 0;
41 tab->var[i].is_redundant = 0;
42 tab->var[i].frozen = 0;
61 tab->bottom.type = isl_tab_undo_bottom;
62 tab->bottom.next = NULL;
63 tab->top = &tab->bottom;
70 int isl_tab_extend_cons(struct isl_tab *tab, unsigned n_new)
72 unsigned off = 2 + tab->M;
73 if (tab->max_con < tab->n_con + n_new) {
74 struct isl_tab_var *con;
76 con = isl_realloc_array(tab->mat->ctx, tab->con,
77 struct isl_tab_var, tab->max_con + n_new);
81 tab->max_con += n_new;
83 if (tab->mat->n_row < tab->n_row + n_new) {
86 tab->mat = isl_mat_extend(tab->mat,
87 tab->n_row + n_new, off + tab->n_col);
90 row_var = isl_realloc_array(tab->mat->ctx, tab->row_var,
91 int, tab->mat->n_row);
94 tab->row_var = row_var;
96 enum isl_tab_row_sign *s;
97 s = isl_realloc_array(tab->mat->ctx, tab->row_sign,
98 enum isl_tab_row_sign, tab->mat->n_row);
107 /* Make room for at least n_new extra variables.
108 * Return -1 if anything went wrong.
110 int isl_tab_extend_vars(struct isl_tab *tab, unsigned n_new)
112 struct isl_tab_var *var;
113 unsigned off = 2 + tab->M;
115 if (tab->max_var < tab->n_var + n_new) {
116 var = isl_realloc_array(tab->mat->ctx, tab->var,
117 struct isl_tab_var, tab->n_var + n_new);
121 tab->max_var += n_new;
124 if (tab->mat->n_col < off + tab->n_col + n_new) {
127 tab->mat = isl_mat_extend(tab->mat,
128 tab->mat->n_row, off + tab->n_col + n_new);
131 p = isl_realloc_array(tab->mat->ctx, tab->col_var,
132 int, tab->mat->n_col);
141 struct isl_tab *isl_tab_extend(struct isl_tab *tab, unsigned n_new)
143 if (isl_tab_extend_cons(tab, n_new) >= 0)
150 static void free_undo(struct isl_tab *tab)
152 struct isl_tab_undo *undo, *next;
154 for (undo = tab->top; undo && undo != &tab->bottom; undo = next) {
161 void isl_tab_free(struct isl_tab *tab)
166 isl_mat_free(tab->mat);
167 isl_vec_free(tab->dual);
168 isl_basic_set_free(tab->bset);
177 struct isl_tab *isl_tab_dup(struct isl_tab *tab)
185 dup = isl_calloc_type(tab->ctx, struct isl_tab);
188 dup->mat = isl_mat_dup(tab->mat);
191 dup->var = isl_alloc_array(tab->ctx, struct isl_tab_var, tab->max_var);
194 for (i = 0; i < tab->n_var; ++i)
195 dup->var[i] = tab->var[i];
196 dup->con = isl_alloc_array(tab->ctx, struct isl_tab_var, tab->max_con);
199 for (i = 0; i < tab->n_con; ++i)
200 dup->con[i] = tab->con[i];
201 dup->col_var = isl_alloc_array(tab->ctx, int, tab->mat->n_col);
204 for (i = 0; i < tab->n_var; ++i)
205 dup->col_var[i] = tab->col_var[i];
206 dup->row_var = isl_alloc_array(tab->ctx, int, tab->mat->n_row);
209 for (i = 0; i < tab->n_row; ++i)
210 dup->row_var[i] = tab->row_var[i];
212 dup->row_sign = isl_alloc_array(tab->ctx, enum isl_tab_row_sign,
216 for (i = 0; i < tab->n_row; ++i)
217 dup->row_sign[i] = tab->row_sign[i];
219 dup->n_row = tab->n_row;
220 dup->n_con = tab->n_con;
221 dup->n_eq = tab->n_eq;
222 dup->max_con = tab->max_con;
223 dup->n_col = tab->n_col;
224 dup->n_var = tab->n_var;
225 dup->max_var = tab->max_var;
226 dup->n_param = tab->n_param;
227 dup->n_div = tab->n_div;
228 dup->n_dead = tab->n_dead;
229 dup->n_redundant = tab->n_redundant;
230 dup->rational = tab->rational;
231 dup->empty = tab->empty;
235 dup->bottom.type = isl_tab_undo_bottom;
236 dup->bottom.next = NULL;
237 dup->top = &dup->bottom;
244 static struct isl_tab_var *var_from_index(struct isl_tab *tab, int i)
249 return &tab->con[~i];
252 struct isl_tab_var *isl_tab_var_from_row(struct isl_tab *tab, int i)
254 return var_from_index(tab, tab->row_var[i]);
257 static struct isl_tab_var *var_from_col(struct isl_tab *tab, int i)
259 return var_from_index(tab, tab->col_var[i]);
262 /* Check if there are any upper bounds on column variable "var",
263 * i.e., non-negative rows where var appears with a negative coefficient.
264 * Return 1 if there are no such bounds.
266 static int max_is_manifestly_unbounded(struct isl_tab *tab,
267 struct isl_tab_var *var)
270 unsigned off = 2 + tab->M;
274 for (i = tab->n_redundant; i < tab->n_row; ++i) {
275 if (!isl_int_is_neg(tab->mat->row[i][off + var->index]))
277 if (isl_tab_var_from_row(tab, i)->is_nonneg)
283 /* Check if there are any lower bounds on column variable "var",
284 * i.e., non-negative rows where var appears with a positive coefficient.
285 * Return 1 if there are no such bounds.
287 static int min_is_manifestly_unbounded(struct isl_tab *tab,
288 struct isl_tab_var *var)
291 unsigned off = 2 + tab->M;
295 for (i = tab->n_redundant; i < tab->n_row; ++i) {
296 if (!isl_int_is_pos(tab->mat->row[i][off + var->index]))
298 if (isl_tab_var_from_row(tab, i)->is_nonneg)
304 static int row_cmp(struct isl_tab *tab, int r1, int r2, int c, isl_int t)
306 unsigned off = 2 + tab->M;
310 isl_int_mul(t, tab->mat->row[r1][2], tab->mat->row[r2][off+c]);
311 isl_int_submul(t, tab->mat->row[r2][2], tab->mat->row[r1][off+c]);
316 isl_int_mul(t, tab->mat->row[r1][1], tab->mat->row[r2][off + c]);
317 isl_int_submul(t, tab->mat->row[r2][1], tab->mat->row[r1][off + c]);
318 return isl_int_sgn(t);
321 /* Given the index of a column "c", return the index of a row
322 * that can be used to pivot the column in, with either an increase
323 * (sgn > 0) or a decrease (sgn < 0) of the corresponding variable.
324 * If "var" is not NULL, then the row returned will be different from
325 * the one associated with "var".
327 * Each row in the tableau is of the form
329 * x_r = a_r0 + \sum_i a_ri x_i
331 * Only rows with x_r >= 0 and with the sign of a_ri opposite to "sgn"
332 * impose any limit on the increase or decrease in the value of x_c
333 * and this bound is equal to a_r0 / |a_rc|. We are therefore looking
334 * for the row with the smallest (most stringent) such bound.
335 * Note that the common denominator of each row drops out of the fraction.
336 * To check if row j has a smaller bound than row r, i.e.,
337 * a_j0 / |a_jc| < a_r0 / |a_rc| or a_j0 |a_rc| < a_r0 |a_jc|,
338 * we check if -sign(a_jc) (a_j0 a_rc - a_r0 a_jc) < 0,
339 * where -sign(a_jc) is equal to "sgn".
341 static int pivot_row(struct isl_tab *tab,
342 struct isl_tab_var *var, int sgn, int c)
346 unsigned off = 2 + tab->M;
350 for (j = tab->n_redundant; j < tab->n_row; ++j) {
351 if (var && j == var->index)
353 if (!isl_tab_var_from_row(tab, j)->is_nonneg)
355 if (sgn * isl_int_sgn(tab->mat->row[j][off + c]) >= 0)
361 tsgn = sgn * row_cmp(tab, r, j, c, t);
362 if (tsgn < 0 || (tsgn == 0 &&
363 tab->row_var[j] < tab->row_var[r]))
370 /* Find a pivot (row and col) that will increase (sgn > 0) or decrease
371 * (sgn < 0) the value of row variable var.
372 * If not NULL, then skip_var is a row variable that should be ignored
373 * while looking for a pivot row. It is usually equal to var.
375 * As the given row in the tableau is of the form
377 * x_r = a_r0 + \sum_i a_ri x_i
379 * we need to find a column such that the sign of a_ri is equal to "sgn"
380 * (such that an increase in x_i will have the desired effect) or a
381 * column with a variable that may attain negative values.
382 * If a_ri is positive, then we need to move x_i in the same direction
383 * to obtain the desired effect. Otherwise, x_i has to move in the
384 * opposite direction.
386 static void find_pivot(struct isl_tab *tab,
387 struct isl_tab_var *var, struct isl_tab_var *skip_var,
388 int sgn, int *row, int *col)
395 isl_assert(tab->mat->ctx, var->is_row, return);
396 tr = tab->mat->row[var->index] + 2 + tab->M;
399 for (j = tab->n_dead; j < tab->n_col; ++j) {
400 if (isl_int_is_zero(tr[j]))
402 if (isl_int_sgn(tr[j]) != sgn &&
403 var_from_col(tab, j)->is_nonneg)
405 if (c < 0 || tab->col_var[j] < tab->col_var[c])
411 sgn *= isl_int_sgn(tr[c]);
412 r = pivot_row(tab, skip_var, sgn, c);
413 *row = r < 0 ? var->index : r;
417 /* Return 1 if row "row" represents an obviously redundant inequality.
419 * - it represents an inequality or a variable
420 * - that is the sum of a non-negative sample value and a positive
421 * combination of zero or more non-negative variables.
423 int isl_tab_row_is_redundant(struct isl_tab *tab, int row)
426 unsigned off = 2 + tab->M;
428 if (tab->row_var[row] < 0 && !isl_tab_var_from_row(tab, row)->is_nonneg)
431 if (isl_int_is_neg(tab->mat->row[row][1]))
433 if (tab->M && isl_int_is_neg(tab->mat->row[row][2]))
436 for (i = tab->n_dead; i < tab->n_col; ++i) {
437 if (isl_int_is_zero(tab->mat->row[row][off + i]))
439 if (isl_int_is_neg(tab->mat->row[row][off + i]))
441 if (!var_from_col(tab, i)->is_nonneg)
447 static void swap_rows(struct isl_tab *tab, int row1, int row2)
450 t = tab->row_var[row1];
451 tab->row_var[row1] = tab->row_var[row2];
452 tab->row_var[row2] = t;
453 isl_tab_var_from_row(tab, row1)->index = row1;
454 isl_tab_var_from_row(tab, row2)->index = row2;
455 tab->mat = isl_mat_swap_rows(tab->mat, row1, row2);
459 t = tab->row_sign[row1];
460 tab->row_sign[row1] = tab->row_sign[row2];
461 tab->row_sign[row2] = t;
464 static void push_union(struct isl_tab *tab,
465 enum isl_tab_undo_type type, union isl_tab_undo_val u)
467 struct isl_tab_undo *undo;
472 undo = isl_alloc_type(tab->mat->ctx, struct isl_tab_undo);
480 undo->next = tab->top;
484 void isl_tab_push_var(struct isl_tab *tab,
485 enum isl_tab_undo_type type, struct isl_tab_var *var)
487 union isl_tab_undo_val u;
489 u.var_index = tab->row_var[var->index];
491 u.var_index = tab->col_var[var->index];
492 push_union(tab, type, u);
495 void isl_tab_push(struct isl_tab *tab, enum isl_tab_undo_type type)
497 union isl_tab_undo_val u = { 0 };
498 push_union(tab, type, u);
501 /* Push a record on the undo stack describing the current basic
502 * variables, so that the this state can be restored during rollback.
504 void isl_tab_push_basis(struct isl_tab *tab)
507 union isl_tab_undo_val u;
509 u.col_var = isl_alloc_array(tab->mat->ctx, int, tab->n_col);
515 for (i = 0; i < tab->n_col; ++i)
516 u.col_var[i] = tab->col_var[i];
517 push_union(tab, isl_tab_undo_saved_basis, u);
520 /* Mark row with index "row" as being redundant.
521 * If we may need to undo the operation or if the row represents
522 * a variable of the original problem, the row is kept,
523 * but no longer considered when looking for a pivot row.
524 * Otherwise, the row is simply removed.
526 * The row may be interchanged with some other row. If it
527 * is interchanged with a later row, return 1. Otherwise return 0.
528 * If the rows are checked in order in the calling function,
529 * then a return value of 1 means that the row with the given
530 * row number may now contain a different row that hasn't been checked yet.
532 int isl_tab_mark_redundant(struct isl_tab *tab, int row)
534 struct isl_tab_var *var = isl_tab_var_from_row(tab, row);
535 var->is_redundant = 1;
536 isl_assert(tab->mat->ctx, row >= tab->n_redundant, return);
537 if (tab->need_undo || tab->row_var[row] >= 0) {
538 if (tab->row_var[row] >= 0 && !var->is_nonneg) {
540 isl_tab_push_var(tab, isl_tab_undo_nonneg, var);
542 if (row != tab->n_redundant)
543 swap_rows(tab, row, tab->n_redundant);
544 isl_tab_push_var(tab, isl_tab_undo_redundant, var);
548 if (row != tab->n_row - 1)
549 swap_rows(tab, row, tab->n_row - 1);
550 isl_tab_var_from_row(tab, tab->n_row - 1)->index = -1;
556 struct isl_tab *isl_tab_mark_empty(struct isl_tab *tab)
558 if (!tab->empty && tab->need_undo)
559 isl_tab_push(tab, isl_tab_undo_empty);
564 /* Update the rows signs after a pivot of "row" and "col", with "row_sgn"
565 * the original sign of the pivot element.
566 * We only keep track of row signs during PILP solving and in this case
567 * we only pivot a row with negative sign (meaning the value is always
568 * non-positive) using a positive pivot element.
570 * For each row j, the new value of the parametric constant is equal to
572 * a_j0 - a_jc a_r0/a_rc
574 * where a_j0 is the original parametric constant, a_rc is the pivot element,
575 * a_r0 is the parametric constant of the pivot row and a_jc is the
576 * pivot column entry of the row j.
577 * Since a_r0 is non-positive and a_rc is positive, the sign of row j
578 * remains the same if a_jc has the same sign as the row j or if
579 * a_jc is zero. In all other cases, we reset the sign to "unknown".
581 static void update_row_sign(struct isl_tab *tab, int row, int col, int row_sgn)
584 struct isl_mat *mat = tab->mat;
585 unsigned off = 2 + tab->M;
590 if (tab->row_sign[row] == 0)
592 isl_assert(mat->ctx, row_sgn > 0, return);
593 isl_assert(mat->ctx, tab->row_sign[row] == isl_tab_row_neg, return);
594 tab->row_sign[row] = isl_tab_row_pos;
595 for (i = 0; i < tab->n_row; ++i) {
599 s = isl_int_sgn(mat->row[i][off + col]);
602 if (!tab->row_sign[i])
604 if (s < 0 && tab->row_sign[i] == isl_tab_row_neg)
606 if (s > 0 && tab->row_sign[i] == isl_tab_row_pos)
608 tab->row_sign[i] = isl_tab_row_unknown;
612 /* Given a row number "row" and a column number "col", pivot the tableau
613 * such that the associated variables are interchanged.
614 * The given row in the tableau expresses
616 * x_r = a_r0 + \sum_i a_ri x_i
620 * x_c = 1/a_rc x_r - a_r0/a_rc + sum_{i \ne r} -a_ri/a_rc
622 * Substituting this equality into the other rows
624 * x_j = a_j0 + \sum_i a_ji x_i
626 * with a_jc \ne 0, we obtain
628 * x_j = a_jc/a_rc x_r + a_j0 - a_jc a_r0/a_rc + sum a_ji - a_jc a_ri/a_rc
635 * where i is any other column and j is any other row,
636 * is therefore transformed into
638 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
639 * s(n_rc)d_r n_jc/(|n_rc| d_j) (n_ji |n_rc| - s(n_rc)n_jc n_ri)/(|n_rc| d_j)
641 * The transformation is performed along the following steps
646 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
649 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
650 * n_jc/(|n_rc| d_j) n_ji/(|n_rc| d_j)
652 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
653 * n_jc/(|n_rc| d_j) (n_ji |n_rc|)/(|n_rc| d_j)
655 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
656 * n_jc/(|n_rc| d_j) (n_ji |n_rc| - s(n_rc)n_jc n_ri)/(|n_rc| d_j)
658 * s(n_rc)d_r/|n_rc| -s(n_rc)n_ri/|n_rc|
659 * s(n_rc)d_r n_jc/(|n_rc| d_j) (n_ji |n_rc| - s(n_rc)n_jc n_ri)/(|n_rc| d_j)
662 void isl_tab_pivot(struct isl_tab *tab, int row, int col)
667 struct isl_mat *mat = tab->mat;
668 struct isl_tab_var *var;
669 unsigned off = 2 + tab->M;
671 isl_int_swap(mat->row[row][0], mat->row[row][off + col]);
672 sgn = isl_int_sgn(mat->row[row][0]);
674 isl_int_neg(mat->row[row][0], mat->row[row][0]);
675 isl_int_neg(mat->row[row][off + col], mat->row[row][off + col]);
677 for (j = 0; j < off - 1 + tab->n_col; ++j) {
678 if (j == off - 1 + col)
680 isl_int_neg(mat->row[row][1 + j], mat->row[row][1 + j]);
682 if (!isl_int_is_one(mat->row[row][0]))
683 isl_seq_normalize(mat->row[row], off + tab->n_col);
684 for (i = 0; i < tab->n_row; ++i) {
687 if (isl_int_is_zero(mat->row[i][off + col]))
689 isl_int_mul(mat->row[i][0], mat->row[i][0], mat->row[row][0]);
690 for (j = 0; j < off - 1 + tab->n_col; ++j) {
691 if (j == off - 1 + col)
693 isl_int_mul(mat->row[i][1 + j],
694 mat->row[i][1 + j], mat->row[row][0]);
695 isl_int_addmul(mat->row[i][1 + j],
696 mat->row[i][off + col], mat->row[row][1 + j]);
698 isl_int_mul(mat->row[i][off + col],
699 mat->row[i][off + col], mat->row[row][off + col]);
700 if (!isl_int_is_one(mat->row[i][0]))
701 isl_seq_normalize(mat->row[i], off + tab->n_col);
703 t = tab->row_var[row];
704 tab->row_var[row] = tab->col_var[col];
705 tab->col_var[col] = t;
706 var = isl_tab_var_from_row(tab, row);
709 var = var_from_col(tab, col);
712 update_row_sign(tab, row, col, sgn);
715 for (i = tab->n_redundant; i < tab->n_row; ++i) {
716 if (isl_int_is_zero(mat->row[i][off + col]))
718 if (!isl_tab_var_from_row(tab, i)->frozen &&
719 isl_tab_row_is_redundant(tab, i))
720 if (isl_tab_mark_redundant(tab, i))
725 /* If "var" represents a column variable, then pivot is up (sgn > 0)
726 * or down (sgn < 0) to a row. The variable is assumed not to be
727 * unbounded in the specified direction.
728 * If sgn = 0, then the variable is unbounded in both directions,
729 * and we pivot with any row we can find.
731 static void to_row(struct isl_tab *tab, struct isl_tab_var *var, int sign)
734 unsigned off = 2 + tab->M;
740 for (r = tab->n_redundant; r < tab->n_row; ++r)
741 if (!isl_int_is_zero(tab->mat->row[r][off+var->index]))
743 isl_assert(tab->mat->ctx, r < tab->n_row, return);
745 r = pivot_row(tab, NULL, sign, var->index);
746 isl_assert(tab->mat->ctx, r >= 0, return);
749 isl_tab_pivot(tab, r, var->index);
752 static void check_table(struct isl_tab *tab)
758 for (i = 0; i < tab->n_row; ++i) {
759 if (!isl_tab_var_from_row(tab, i)->is_nonneg)
761 assert(!isl_int_is_neg(tab->mat->row[i][1]));
765 /* Return the sign of the maximal value of "var".
766 * If the sign is not negative, then on return from this function,
767 * the sample value will also be non-negative.
769 * If "var" is manifestly unbounded wrt positive values, we are done.
770 * Otherwise, we pivot the variable up to a row if needed
771 * Then we continue pivoting down until either
772 * - no more down pivots can be performed
773 * - the sample value is positive
774 * - the variable is pivoted into a manifestly unbounded column
776 static int sign_of_max(struct isl_tab *tab, struct isl_tab_var *var)
780 if (max_is_manifestly_unbounded(tab, var))
783 while (!isl_int_is_pos(tab->mat->row[var->index][1])) {
784 find_pivot(tab, var, var, 1, &row, &col);
786 return isl_int_sgn(tab->mat->row[var->index][1]);
787 isl_tab_pivot(tab, row, col);
788 if (!var->is_row) /* manifestly unbounded */
794 static int row_is_neg(struct isl_tab *tab, int row)
797 return isl_int_is_neg(tab->mat->row[row][1]);
798 if (isl_int_is_pos(tab->mat->row[row][2]))
800 if (isl_int_is_neg(tab->mat->row[row][2]))
802 return isl_int_is_neg(tab->mat->row[row][1]);
805 static int row_sgn(struct isl_tab *tab, int row)
808 return isl_int_sgn(tab->mat->row[row][1]);
809 if (!isl_int_is_zero(tab->mat->row[row][2]))
810 return isl_int_sgn(tab->mat->row[row][2]);
812 return isl_int_sgn(tab->mat->row[row][1]);
815 /* Perform pivots until the row variable "var" has a non-negative
816 * sample value or until no more upward pivots can be performed.
817 * Return the sign of the sample value after the pivots have been
820 static int restore_row(struct isl_tab *tab, struct isl_tab_var *var)
824 while (row_is_neg(tab, var->index)) {
825 find_pivot(tab, var, var, 1, &row, &col);
828 isl_tab_pivot(tab, row, col);
829 if (!var->is_row) /* manifestly unbounded */
832 return row_sgn(tab, var->index);
835 /* Perform pivots until we are sure that the row variable "var"
836 * can attain non-negative values. After return from this
837 * function, "var" is still a row variable, but its sample
838 * value may not be non-negative, even if the function returns 1.
840 static int at_least_zero(struct isl_tab *tab, struct isl_tab_var *var)
844 while (isl_int_is_neg(tab->mat->row[var->index][1])) {
845 find_pivot(tab, var, var, 1, &row, &col);
848 if (row == var->index) /* manifestly unbounded */
850 isl_tab_pivot(tab, row, col);
852 return !isl_int_is_neg(tab->mat->row[var->index][1]);
855 /* Return a negative value if "var" can attain negative values.
856 * Return a non-negative value otherwise.
858 * If "var" is manifestly unbounded wrt negative values, we are done.
859 * Otherwise, if var is in a column, we can pivot it down to a row.
860 * Then we continue pivoting down until either
861 * - the pivot would result in a manifestly unbounded column
862 * => we don't perform the pivot, but simply return -1
863 * - no more down pivots can be performed
864 * - the sample value is negative
865 * If the sample value becomes negative and the variable is supposed
866 * to be nonnegative, then we undo the last pivot.
867 * However, if the last pivot has made the pivoting variable
868 * obviously redundant, then it may have moved to another row.
869 * In that case we look for upward pivots until we reach a non-negative
872 static int sign_of_min(struct isl_tab *tab, struct isl_tab_var *var)
875 struct isl_tab_var *pivot_var;
877 if (min_is_manifestly_unbounded(tab, var))
881 row = pivot_row(tab, NULL, -1, col);
882 pivot_var = var_from_col(tab, col);
883 isl_tab_pivot(tab, row, col);
884 if (var->is_redundant)
886 if (isl_int_is_neg(tab->mat->row[var->index][1])) {
887 if (var->is_nonneg) {
888 if (!pivot_var->is_redundant &&
889 pivot_var->index == row)
890 isl_tab_pivot(tab, row, col);
892 restore_row(tab, var);
897 if (var->is_redundant)
899 while (!isl_int_is_neg(tab->mat->row[var->index][1])) {
900 find_pivot(tab, var, var, -1, &row, &col);
901 if (row == var->index)
904 return isl_int_sgn(tab->mat->row[var->index][1]);
905 pivot_var = var_from_col(tab, col);
906 isl_tab_pivot(tab, row, col);
907 if (var->is_redundant)
910 if (var->is_nonneg) {
911 /* pivot back to non-negative value */
912 if (!pivot_var->is_redundant && pivot_var->index == row)
913 isl_tab_pivot(tab, row, col);
915 restore_row(tab, var);
920 static int row_at_most_neg_one(struct isl_tab *tab, int row)
923 if (isl_int_is_pos(tab->mat->row[row][2]))
925 if (isl_int_is_neg(tab->mat->row[row][2]))
928 return isl_int_is_neg(tab->mat->row[row][1]) &&
929 isl_int_abs_ge(tab->mat->row[row][1],
930 tab->mat->row[row][0]);
933 /* Return 1 if "var" can attain values <= -1.
934 * Return 0 otherwise.
936 * The sample value of "var" is assumed to be non-negative when the
937 * the function is called and will be made non-negative again before
938 * the function returns.
940 int isl_tab_min_at_most_neg_one(struct isl_tab *tab, struct isl_tab_var *var)
943 struct isl_tab_var *pivot_var;
945 if (min_is_manifestly_unbounded(tab, var))
949 row = pivot_row(tab, NULL, -1, col);
950 pivot_var = var_from_col(tab, col);
951 isl_tab_pivot(tab, row, col);
952 if (var->is_redundant)
954 if (row_at_most_neg_one(tab, var->index)) {
955 if (var->is_nonneg) {
956 if (!pivot_var->is_redundant &&
957 pivot_var->index == row)
958 isl_tab_pivot(tab, row, col);
960 restore_row(tab, var);
965 if (var->is_redundant)
968 find_pivot(tab, var, var, -1, &row, &col);
969 if (row == var->index)
973 pivot_var = var_from_col(tab, col);
974 isl_tab_pivot(tab, row, col);
975 if (var->is_redundant)
977 } while (!row_at_most_neg_one(tab, var->index));
978 if (var->is_nonneg) {
979 /* pivot back to non-negative value */
980 if (!pivot_var->is_redundant && pivot_var->index == row)
981 isl_tab_pivot(tab, row, col);
982 restore_row(tab, var);
987 /* Return 1 if "var" can attain values >= 1.
988 * Return 0 otherwise.
990 static int at_least_one(struct isl_tab *tab, struct isl_tab_var *var)
995 if (max_is_manifestly_unbounded(tab, var))
998 r = tab->mat->row[var->index];
999 while (isl_int_lt(r[1], r[0])) {
1000 find_pivot(tab, var, var, 1, &row, &col);
1002 return isl_int_ge(r[1], r[0]);
1003 if (row == var->index) /* manifestly unbounded */
1005 isl_tab_pivot(tab, row, col);
1010 static void swap_cols(struct isl_tab *tab, int col1, int col2)
1013 unsigned off = 2 + tab->M;
1014 t = tab->col_var[col1];
1015 tab->col_var[col1] = tab->col_var[col2];
1016 tab->col_var[col2] = t;
1017 var_from_col(tab, col1)->index = col1;
1018 var_from_col(tab, col2)->index = col2;
1019 tab->mat = isl_mat_swap_cols(tab->mat, off + col1, off + col2);
1022 /* Mark column with index "col" as representing a zero variable.
1023 * If we may need to undo the operation the column is kept,
1024 * but no longer considered.
1025 * Otherwise, the column is simply removed.
1027 * The column may be interchanged with some other column. If it
1028 * is interchanged with a later column, return 1. Otherwise return 0.
1029 * If the columns are checked in order in the calling function,
1030 * then a return value of 1 means that the column with the given
1031 * column number may now contain a different column that
1032 * hasn't been checked yet.
1034 int isl_tab_kill_col(struct isl_tab *tab, int col)
1036 var_from_col(tab, col)->is_zero = 1;
1037 if (tab->need_undo) {
1038 isl_tab_push_var(tab, isl_tab_undo_zero, var_from_col(tab, col));
1039 if (col != tab->n_dead)
1040 swap_cols(tab, col, tab->n_dead);
1044 if (col != tab->n_col - 1)
1045 swap_cols(tab, col, tab->n_col - 1);
1046 var_from_col(tab, tab->n_col - 1)->index = -1;
1052 /* Row variable "var" is non-negative and cannot attain any values
1053 * larger than zero. This means that the coefficients of the unrestricted
1054 * column variables are zero and that the coefficients of the non-negative
1055 * column variables are zero or negative.
1056 * Each of the non-negative variables with a negative coefficient can
1057 * then also be written as the negative sum of non-negative variables
1058 * and must therefore also be zero.
1060 static void close_row(struct isl_tab *tab, struct isl_tab_var *var)
1063 struct isl_mat *mat = tab->mat;
1064 unsigned off = 2 + tab->M;
1066 isl_assert(tab->mat->ctx, var->is_nonneg, return);
1068 for (j = tab->n_dead; j < tab->n_col; ++j) {
1069 if (isl_int_is_zero(mat->row[var->index][off + j]))
1071 isl_assert(tab->mat->ctx,
1072 isl_int_is_neg(mat->row[var->index][off + j]), return);
1073 if (isl_tab_kill_col(tab, j))
1076 isl_tab_mark_redundant(tab, var->index);
1079 /* Add a constraint to the tableau and allocate a row for it.
1080 * Return the index into the constraint array "con".
1082 int isl_tab_allocate_con(struct isl_tab *tab)
1086 isl_assert(tab->mat->ctx, tab->n_row < tab->mat->n_row, return -1);
1089 tab->con[r].index = tab->n_row;
1090 tab->con[r].is_row = 1;
1091 tab->con[r].is_nonneg = 0;
1092 tab->con[r].is_zero = 0;
1093 tab->con[r].is_redundant = 0;
1094 tab->con[r].frozen = 0;
1095 tab->row_var[tab->n_row] = ~r;
1099 isl_tab_push_var(tab, isl_tab_undo_allocate, &tab->con[r]);
1104 /* Add a variable to the tableau and allocate a column for it.
1105 * Return the index into the variable array "var".
1107 int isl_tab_allocate_var(struct isl_tab *tab)
1111 unsigned off = 2 + tab->M;
1113 isl_assert(tab->mat->ctx, tab->n_col < tab->mat->n_col, return -1);
1114 isl_assert(tab->mat->ctx, tab->n_var < tab->max_var, return -1);
1117 tab->var[r].index = tab->n_col;
1118 tab->var[r].is_row = 0;
1119 tab->var[r].is_nonneg = 0;
1120 tab->var[r].is_zero = 0;
1121 tab->var[r].is_redundant = 0;
1122 tab->var[r].frozen = 0;
1123 tab->col_var[tab->n_col] = r;
1125 for (i = 0; i < tab->n_row; ++i)
1126 isl_int_set_si(tab->mat->row[i][off + tab->n_col], 0);
1130 isl_tab_push_var(tab, isl_tab_undo_allocate, &tab->var[r]);
1135 /* Add a row to the tableau. The row is given as an affine combination
1136 * of the original variables and needs to be expressed in terms of the
1139 * We add each term in turn.
1140 * If r = n/d_r is the current sum and we need to add k x, then
1141 * if x is a column variable, we increase the numerator of
1142 * this column by k d_r
1143 * if x = f/d_x is a row variable, then the new representation of r is
1145 * n k f d_x/g n + d_r/g k f m/d_r n + m/d_g k f
1146 * --- + --- = ------------------- = -------------------
1147 * d_r d_r d_r d_x/g m
1149 * with g the gcd of d_r and d_x and m the lcm of d_r and d_x.
1151 int isl_tab_add_row(struct isl_tab *tab, isl_int *line)
1157 unsigned off = 2 + tab->M;
1159 r = isl_tab_allocate_con(tab);
1165 row = tab->mat->row[tab->con[r].index];
1166 isl_int_set_si(row[0], 1);
1167 isl_int_set(row[1], line[0]);
1168 isl_seq_clr(row + 2, tab->M + tab->n_col);
1169 for (i = 0; i < tab->n_var; ++i) {
1170 if (tab->var[i].is_zero)
1172 if (tab->var[i].is_row) {
1174 row[0], tab->mat->row[tab->var[i].index][0]);
1175 isl_int_swap(a, row[0]);
1176 isl_int_divexact(a, row[0], a);
1178 row[0], tab->mat->row[tab->var[i].index][0]);
1179 isl_int_mul(b, b, line[1 + i]);
1180 isl_seq_combine(row + 1, a, row + 1,
1181 b, tab->mat->row[tab->var[i].index] + 1,
1182 1 + tab->M + tab->n_col);
1184 isl_int_addmul(row[off + tab->var[i].index],
1185 line[1 + i], row[0]);
1186 if (tab->M && i >= tab->n_param && i < tab->n_var - tab->n_div)
1187 isl_int_submul(row[2], line[1 + i], row[0]);
1189 isl_seq_normalize(row, off + tab->n_col);
1194 tab->row_sign[tab->con[r].index] = 0;
1199 static int drop_row(struct isl_tab *tab, int row)
1201 isl_assert(tab->mat->ctx, ~tab->row_var[row] == tab->n_con - 1, return -1);
1202 if (row != tab->n_row - 1)
1203 swap_rows(tab, row, tab->n_row - 1);
1209 static int drop_col(struct isl_tab *tab, int col)
1211 isl_assert(tab->mat->ctx, tab->col_var[col] == tab->n_var - 1, return -1);
1212 if (col != tab->n_col - 1)
1213 swap_cols(tab, col, tab->n_col - 1);
1219 /* Add inequality "ineq" and check if it conflicts with the
1220 * previously added constraints or if it is obviously redundant.
1222 struct isl_tab *isl_tab_add_ineq(struct isl_tab *tab, isl_int *ineq)
1229 r = isl_tab_add_row(tab, ineq);
1232 tab->con[r].is_nonneg = 1;
1233 isl_tab_push_var(tab, isl_tab_undo_nonneg, &tab->con[r]);
1234 if (isl_tab_row_is_redundant(tab, tab->con[r].index)) {
1235 isl_tab_mark_redundant(tab, tab->con[r].index);
1239 sgn = restore_row(tab, &tab->con[r]);
1241 return isl_tab_mark_empty(tab);
1242 if (tab->con[r].is_row && isl_tab_row_is_redundant(tab, tab->con[r].index))
1243 isl_tab_mark_redundant(tab, tab->con[r].index);
1250 /* Pivot a non-negative variable down until it reaches the value zero
1251 * and then pivot the variable into a column position.
1253 int to_col(struct isl_tab *tab, struct isl_tab_var *var)
1257 unsigned off = 2 + tab->M;
1262 while (isl_int_is_pos(tab->mat->row[var->index][1])) {
1263 find_pivot(tab, var, NULL, -1, &row, &col);
1264 isl_assert(tab->mat->ctx, row != -1, return -1);
1265 isl_tab_pivot(tab, row, col);
1270 for (i = tab->n_dead; i < tab->n_col; ++i)
1271 if (!isl_int_is_zero(tab->mat->row[var->index][off + i]))
1274 isl_assert(tab->mat->ctx, i < tab->n_col, return -1);
1275 isl_tab_pivot(tab, var->index, i);
1280 /* We assume Gaussian elimination has been performed on the equalities.
1281 * The equalities can therefore never conflict.
1282 * Adding the equalities is currently only really useful for a later call
1283 * to isl_tab_ineq_type.
1285 static struct isl_tab *add_eq(struct isl_tab *tab, isl_int *eq)
1292 r = isl_tab_add_row(tab, eq);
1296 r = tab->con[r].index;
1297 i = isl_seq_first_non_zero(tab->mat->row[r] + 2 + tab->M + tab->n_dead,
1298 tab->n_col - tab->n_dead);
1299 isl_assert(tab->mat->ctx, i >= 0, goto error);
1301 isl_tab_pivot(tab, r, i);
1302 isl_tab_kill_col(tab, i);
1311 /* Add an equality that is known to be valid for the given tableau.
1313 struct isl_tab *isl_tab_add_valid_eq(struct isl_tab *tab, isl_int *eq)
1315 struct isl_tab_var *var;
1321 r = isl_tab_add_row(tab, eq);
1327 if (isl_int_is_neg(tab->mat->row[r][1]))
1328 isl_seq_neg(tab->mat->row[r] + 1, tab->mat->row[r] + 1,
1331 if (to_col(tab, var) < 0)
1334 isl_tab_kill_col(tab, var->index);
1342 struct isl_tab *isl_tab_from_basic_map(struct isl_basic_map *bmap)
1345 struct isl_tab *tab;
1349 tab = isl_tab_alloc(bmap->ctx,
1350 isl_basic_map_total_dim(bmap) + bmap->n_ineq + 1,
1351 isl_basic_map_total_dim(bmap), 0);
1354 tab->rational = ISL_F_ISSET(bmap, ISL_BASIC_MAP_RATIONAL);
1355 if (ISL_F_ISSET(bmap, ISL_BASIC_MAP_EMPTY))
1356 return isl_tab_mark_empty(tab);
1357 for (i = 0; i < bmap->n_eq; ++i) {
1358 tab = add_eq(tab, bmap->eq[i]);
1362 for (i = 0; i < bmap->n_ineq; ++i) {
1363 tab = isl_tab_add_ineq(tab, bmap->ineq[i]);
1364 if (!tab || tab->empty)
1370 struct isl_tab *isl_tab_from_basic_set(struct isl_basic_set *bset)
1372 return isl_tab_from_basic_map((struct isl_basic_map *)bset);
1375 /* Construct a tableau corresponding to the recession cone of "bmap".
1377 struct isl_tab *isl_tab_from_recession_cone(struct isl_basic_map *bmap)
1381 struct isl_tab *tab;
1385 tab = isl_tab_alloc(bmap->ctx, bmap->n_eq + bmap->n_ineq,
1386 isl_basic_map_total_dim(bmap), 0);
1389 tab->rational = ISL_F_ISSET(bmap, ISL_BASIC_MAP_RATIONAL);
1392 for (i = 0; i < bmap->n_eq; ++i) {
1393 isl_int_swap(bmap->eq[i][0], cst);
1394 tab = add_eq(tab, bmap->eq[i]);
1395 isl_int_swap(bmap->eq[i][0], cst);
1399 for (i = 0; i < bmap->n_ineq; ++i) {
1401 isl_int_swap(bmap->ineq[i][0], cst);
1402 r = isl_tab_add_row(tab, bmap->ineq[i]);
1403 isl_int_swap(bmap->ineq[i][0], cst);
1406 tab->con[r].is_nonneg = 1;
1407 isl_tab_push_var(tab, isl_tab_undo_nonneg, &tab->con[r]);
1418 /* Assuming "tab" is the tableau of a cone, check if the cone is
1419 * bounded, i.e., if it is empty or only contains the origin.
1421 int isl_tab_cone_is_bounded(struct isl_tab *tab)
1429 if (tab->n_dead == tab->n_col)
1433 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1434 struct isl_tab_var *var;
1435 var = isl_tab_var_from_row(tab, i);
1436 if (!var->is_nonneg)
1438 if (sign_of_max(tab, var) != 0)
1440 close_row(tab, var);
1443 if (tab->n_dead == tab->n_col)
1445 if (i == tab->n_row)
1450 int isl_tab_sample_is_integer(struct isl_tab *tab)
1457 for (i = 0; i < tab->n_var; ++i) {
1459 if (!tab->var[i].is_row)
1461 row = tab->var[i].index;
1462 if (!isl_int_is_divisible_by(tab->mat->row[row][1],
1463 tab->mat->row[row][0]))
1469 static struct isl_vec *extract_integer_sample(struct isl_tab *tab)
1472 struct isl_vec *vec;
1474 vec = isl_vec_alloc(tab->mat->ctx, 1 + tab->n_var);
1478 isl_int_set_si(vec->block.data[0], 1);
1479 for (i = 0; i < tab->n_var; ++i) {
1480 if (!tab->var[i].is_row)
1481 isl_int_set_si(vec->block.data[1 + i], 0);
1483 int row = tab->var[i].index;
1484 isl_int_divexact(vec->block.data[1 + i],
1485 tab->mat->row[row][1], tab->mat->row[row][0]);
1492 struct isl_vec *isl_tab_get_sample_value(struct isl_tab *tab)
1495 struct isl_vec *vec;
1501 vec = isl_vec_alloc(tab->mat->ctx, 1 + tab->n_var);
1507 isl_int_set_si(vec->block.data[0], 1);
1508 for (i = 0; i < tab->n_var; ++i) {
1510 if (!tab->var[i].is_row) {
1511 isl_int_set_si(vec->block.data[1 + i], 0);
1514 row = tab->var[i].index;
1515 isl_int_gcd(m, vec->block.data[0], tab->mat->row[row][0]);
1516 isl_int_divexact(m, tab->mat->row[row][0], m);
1517 isl_seq_scale(vec->block.data, vec->block.data, m, 1 + i);
1518 isl_int_divexact(m, vec->block.data[0], tab->mat->row[row][0]);
1519 isl_int_mul(vec->block.data[1 + i], m, tab->mat->row[row][1]);
1521 isl_seq_normalize(vec->block.data, vec->size);
1527 /* Update "bmap" based on the results of the tableau "tab".
1528 * In particular, implicit equalities are made explicit, redundant constraints
1529 * are removed and if the sample value happens to be integer, it is stored
1530 * in "bmap" (unless "bmap" already had an integer sample).
1532 * The tableau is assumed to have been created from "bmap" using
1533 * isl_tab_from_basic_map.
1535 struct isl_basic_map *isl_basic_map_update_from_tab(struct isl_basic_map *bmap,
1536 struct isl_tab *tab)
1548 bmap = isl_basic_map_set_to_empty(bmap);
1550 for (i = bmap->n_ineq - 1; i >= 0; --i) {
1551 if (isl_tab_is_equality(tab, n_eq + i))
1552 isl_basic_map_inequality_to_equality(bmap, i);
1553 else if (isl_tab_is_redundant(tab, n_eq + i))
1554 isl_basic_map_drop_inequality(bmap, i);
1556 if (!tab->rational &&
1557 !bmap->sample && isl_tab_sample_is_integer(tab))
1558 bmap->sample = extract_integer_sample(tab);
1562 struct isl_basic_set *isl_basic_set_update_from_tab(struct isl_basic_set *bset,
1563 struct isl_tab *tab)
1565 return (struct isl_basic_set *)isl_basic_map_update_from_tab(
1566 (struct isl_basic_map *)bset, tab);
1569 /* Given a non-negative variable "var", add a new non-negative variable
1570 * that is the opposite of "var", ensuring that var can only attain the
1572 * If var = n/d is a row variable, then the new variable = -n/d.
1573 * If var is a column variables, then the new variable = -var.
1574 * If the new variable cannot attain non-negative values, then
1575 * the resulting tableau is empty.
1576 * Otherwise, we know the value will be zero and we close the row.
1578 static struct isl_tab *cut_to_hyperplane(struct isl_tab *tab,
1579 struct isl_tab_var *var)
1584 unsigned off = 2 + tab->M;
1586 if (isl_tab_extend_cons(tab, 1) < 0)
1590 tab->con[r].index = tab->n_row;
1591 tab->con[r].is_row = 1;
1592 tab->con[r].is_nonneg = 0;
1593 tab->con[r].is_zero = 0;
1594 tab->con[r].is_redundant = 0;
1595 tab->con[r].frozen = 0;
1596 tab->row_var[tab->n_row] = ~r;
1597 row = tab->mat->row[tab->n_row];
1600 isl_int_set(row[0], tab->mat->row[var->index][0]);
1601 isl_seq_neg(row + 1,
1602 tab->mat->row[var->index] + 1, 1 + tab->n_col);
1604 isl_int_set_si(row[0], 1);
1605 isl_seq_clr(row + 1, 1 + tab->n_col);
1606 isl_int_set_si(row[off + var->index], -1);
1611 isl_tab_push_var(tab, isl_tab_undo_allocate, &tab->con[r]);
1613 sgn = sign_of_max(tab, &tab->con[r]);
1615 return isl_tab_mark_empty(tab);
1616 tab->con[r].is_nonneg = 1;
1617 isl_tab_push_var(tab, isl_tab_undo_nonneg, &tab->con[r]);
1619 close_row(tab, &tab->con[r]);
1627 /* Given a tableau "tab" and an inequality constraint "con" of the tableau,
1628 * relax the inequality by one. That is, the inequality r >= 0 is replaced
1629 * by r' = r + 1 >= 0.
1630 * If r is a row variable, we simply increase the constant term by one
1631 * (taking into account the denominator).
1632 * If r is a column variable, then we need to modify each row that
1633 * refers to r = r' - 1 by substituting this equality, effectively
1634 * subtracting the coefficient of the column from the constant.
1636 struct isl_tab *isl_tab_relax(struct isl_tab *tab, int con)
1638 struct isl_tab_var *var;
1639 unsigned off = 2 + tab->M;
1644 var = &tab->con[con];
1646 if (!var->is_row && !max_is_manifestly_unbounded(tab, var))
1647 to_row(tab, var, 1);
1650 isl_int_add(tab->mat->row[var->index][1],
1651 tab->mat->row[var->index][1], tab->mat->row[var->index][0]);
1655 for (i = 0; i < tab->n_row; ++i) {
1656 if (isl_int_is_zero(tab->mat->row[i][off + var->index]))
1658 isl_int_sub(tab->mat->row[i][1], tab->mat->row[i][1],
1659 tab->mat->row[i][off + var->index]);
1664 isl_tab_push_var(tab, isl_tab_undo_relax, var);
1669 struct isl_tab *isl_tab_select_facet(struct isl_tab *tab, int con)
1674 return cut_to_hyperplane(tab, &tab->con[con]);
1677 static int may_be_equality(struct isl_tab *tab, int row)
1679 unsigned off = 2 + tab->M;
1680 return (tab->rational ? isl_int_is_zero(tab->mat->row[row][1])
1681 : isl_int_lt(tab->mat->row[row][1],
1682 tab->mat->row[row][0])) &&
1683 isl_seq_first_non_zero(tab->mat->row[row] + off + tab->n_dead,
1684 tab->n_col - tab->n_dead) != -1;
1687 /* Check for (near) equalities among the constraints.
1688 * A constraint is an equality if it is non-negative and if
1689 * its maximal value is either
1690 * - zero (in case of rational tableaus), or
1691 * - strictly less than 1 (in case of integer tableaus)
1693 * We first mark all non-redundant and non-dead variables that
1694 * are not frozen and not obviously not an equality.
1695 * Then we iterate over all marked variables if they can attain
1696 * any values larger than zero or at least one.
1697 * If the maximal value is zero, we mark any column variables
1698 * that appear in the row as being zero and mark the row as being redundant.
1699 * Otherwise, if the maximal value is strictly less than one (and the
1700 * tableau is integer), then we restrict the value to being zero
1701 * by adding an opposite non-negative variable.
1703 struct isl_tab *isl_tab_detect_equalities(struct isl_tab *tab)
1712 if (tab->n_dead == tab->n_col)
1716 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1717 struct isl_tab_var *var = isl_tab_var_from_row(tab, i);
1718 var->marked = !var->frozen && var->is_nonneg &&
1719 may_be_equality(tab, i);
1723 for (i = tab->n_dead; i < tab->n_col; ++i) {
1724 struct isl_tab_var *var = var_from_col(tab, i);
1725 var->marked = !var->frozen && var->is_nonneg;
1730 struct isl_tab_var *var;
1731 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1732 var = isl_tab_var_from_row(tab, i);
1736 if (i == tab->n_row) {
1737 for (i = tab->n_dead; i < tab->n_col; ++i) {
1738 var = var_from_col(tab, i);
1742 if (i == tab->n_col)
1747 if (sign_of_max(tab, var) == 0)
1748 close_row(tab, var);
1749 else if (!tab->rational && !at_least_one(tab, var)) {
1750 tab = cut_to_hyperplane(tab, var);
1751 return isl_tab_detect_equalities(tab);
1753 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1754 var = isl_tab_var_from_row(tab, i);
1757 if (may_be_equality(tab, i))
1767 /* Check for (near) redundant constraints.
1768 * A constraint is redundant if it is non-negative and if
1769 * its minimal value (temporarily ignoring the non-negativity) is either
1770 * - zero (in case of rational tableaus), or
1771 * - strictly larger than -1 (in case of integer tableaus)
1773 * We first mark all non-redundant and non-dead variables that
1774 * are not frozen and not obviously negatively unbounded.
1775 * Then we iterate over all marked variables if they can attain
1776 * any values smaller than zero or at most negative one.
1777 * If not, we mark the row as being redundant (assuming it hasn't
1778 * been detected as being obviously redundant in the mean time).
1780 struct isl_tab *isl_tab_detect_redundant(struct isl_tab *tab)
1789 if (tab->n_redundant == tab->n_row)
1793 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1794 struct isl_tab_var *var = isl_tab_var_from_row(tab, i);
1795 var->marked = !var->frozen && var->is_nonneg;
1799 for (i = tab->n_dead; i < tab->n_col; ++i) {
1800 struct isl_tab_var *var = var_from_col(tab, i);
1801 var->marked = !var->frozen && var->is_nonneg &&
1802 !min_is_manifestly_unbounded(tab, var);
1807 struct isl_tab_var *var;
1808 for (i = tab->n_redundant; i < tab->n_row; ++i) {
1809 var = isl_tab_var_from_row(tab, i);
1813 if (i == tab->n_row) {
1814 for (i = tab->n_dead; i < tab->n_col; ++i) {
1815 var = var_from_col(tab, i);
1819 if (i == tab->n_col)
1824 if ((tab->rational ? (sign_of_min(tab, var) >= 0)
1825 : !isl_tab_min_at_most_neg_one(tab, var)) &&
1827 isl_tab_mark_redundant(tab, var->index);
1828 for (i = tab->n_dead; i < tab->n_col; ++i) {
1829 var = var_from_col(tab, i);
1832 if (!min_is_manifestly_unbounded(tab, var))
1842 int isl_tab_is_equality(struct isl_tab *tab, int con)
1849 if (tab->con[con].is_zero)
1851 if (tab->con[con].is_redundant)
1853 if (!tab->con[con].is_row)
1854 return tab->con[con].index < tab->n_dead;
1856 row = tab->con[con].index;
1859 return isl_int_is_zero(tab->mat->row[row][1]) &&
1860 isl_seq_first_non_zero(tab->mat->row[row] + 2 + tab->n_dead,
1861 tab->n_col - tab->n_dead) == -1;
1864 /* Return the minimial value of the affine expression "f" with denominator
1865 * "denom" in *opt, *opt_denom, assuming the tableau is not empty and
1866 * the expression cannot attain arbitrarily small values.
1867 * If opt_denom is NULL, then *opt is rounded up to the nearest integer.
1868 * The return value reflects the nature of the result (empty, unbounded,
1869 * minmimal value returned in *opt).
1871 enum isl_lp_result isl_tab_min(struct isl_tab *tab,
1872 isl_int *f, isl_int denom, isl_int *opt, isl_int *opt_denom,
1876 enum isl_lp_result res = isl_lp_ok;
1877 struct isl_tab_var *var;
1878 struct isl_tab_undo *snap;
1881 return isl_lp_empty;
1883 snap = isl_tab_snap(tab);
1884 r = isl_tab_add_row(tab, f);
1886 return isl_lp_error;
1888 isl_int_mul(tab->mat->row[var->index][0],
1889 tab->mat->row[var->index][0], denom);
1892 find_pivot(tab, var, var, -1, &row, &col);
1893 if (row == var->index) {
1894 res = isl_lp_unbounded;
1899 isl_tab_pivot(tab, row, col);
1901 if (isl_tab_rollback(tab, snap) < 0)
1902 return isl_lp_error;
1903 if (ISL_FL_ISSET(flags, ISL_TAB_SAVE_DUAL)) {
1906 isl_vec_free(tab->dual);
1907 tab->dual = isl_vec_alloc(tab->mat->ctx, 1 + tab->n_con);
1909 return isl_lp_error;
1910 isl_int_set(tab->dual->el[0], tab->mat->row[var->index][0]);
1911 for (i = 0; i < tab->n_con; ++i) {
1912 if (tab->con[i].is_row)
1913 isl_int_set_si(tab->dual->el[1 + i], 0);
1915 int pos = 2 + tab->con[i].index;
1916 isl_int_set(tab->dual->el[1 + i],
1917 tab->mat->row[var->index][pos]);
1921 if (res == isl_lp_ok) {
1923 isl_int_set(*opt, tab->mat->row[var->index][1]);
1924 isl_int_set(*opt_denom, tab->mat->row[var->index][0]);
1926 isl_int_cdiv_q(*opt, tab->mat->row[var->index][1],
1927 tab->mat->row[var->index][0]);
1932 int isl_tab_is_redundant(struct isl_tab *tab, int con)
1939 if (tab->con[con].is_zero)
1941 if (tab->con[con].is_redundant)
1943 return tab->con[con].is_row && tab->con[con].index < tab->n_redundant;
1946 /* Take a snapshot of the tableau that can be restored by s call to
1949 struct isl_tab_undo *isl_tab_snap(struct isl_tab *tab)
1957 /* Undo the operation performed by isl_tab_relax.
1959 static void unrelax(struct isl_tab *tab, struct isl_tab_var *var)
1961 unsigned off = 2 + tab->M;
1963 if (!var->is_row && !max_is_manifestly_unbounded(tab, var))
1964 to_row(tab, var, 1);
1967 isl_int_sub(tab->mat->row[var->index][1],
1968 tab->mat->row[var->index][1], tab->mat->row[var->index][0]);
1972 for (i = 0; i < tab->n_row; ++i) {
1973 if (isl_int_is_zero(tab->mat->row[i][off + var->index]))
1975 isl_int_add(tab->mat->row[i][1], tab->mat->row[i][1],
1976 tab->mat->row[i][off + var->index]);
1982 static void perform_undo_var(struct isl_tab *tab, struct isl_tab_undo *undo)
1984 struct isl_tab_var *var = var_from_index(tab, undo->u.var_index);
1985 switch(undo->type) {
1986 case isl_tab_undo_nonneg:
1989 case isl_tab_undo_redundant:
1990 var->is_redundant = 0;
1993 case isl_tab_undo_zero:
1997 case isl_tab_undo_allocate:
1998 if (undo->u.var_index >= 0) {
1999 isl_assert(tab->mat->ctx, !var->is_row, return);
2000 drop_col(tab, var->index);
2004 if (!max_is_manifestly_unbounded(tab, var))
2005 to_row(tab, var, 1);
2006 else if (!min_is_manifestly_unbounded(tab, var))
2007 to_row(tab, var, -1);
2009 to_row(tab, var, 0);
2011 drop_row(tab, var->index);
2013 case isl_tab_undo_relax:
2019 /* Restore the tableau to the state where the basic variables
2020 * are those in "col_var".
2021 * We first construct a list of variables that are currently in
2022 * the basis, but shouldn't. Then we iterate over all variables
2023 * that should be in the basis and for each one that is currently
2024 * not in the basis, we exchange it with one of the elements of the
2025 * list constructed before.
2026 * We can always find an appropriate variable to pivot with because
2027 * the current basis is mapped to the old basis by a non-singular
2028 * matrix and so we can never end up with a zero row.
2030 static int restore_basis(struct isl_tab *tab, int *col_var)
2034 int *extra = NULL; /* current columns that contain bad stuff */
2035 unsigned off = 2 + tab->M;
2037 extra = isl_alloc_array(tab->mat->ctx, int, tab->n_col);
2040 for (i = 0; i < tab->n_col; ++i) {
2041 for (j = 0; j < tab->n_col; ++j)
2042 if (tab->col_var[i] == col_var[j])
2046 extra[n_extra++] = i;
2048 for (i = 0; i < tab->n_col && n_extra > 0; ++i) {
2049 struct isl_tab_var *var;
2052 for (j = 0; j < tab->n_col; ++j)
2053 if (col_var[i] == tab->col_var[j])
2057 var = var_from_index(tab, col_var[i]);
2059 for (j = 0; j < n_extra; ++j)
2060 if (!isl_int_is_zero(tab->mat->row[row][off+extra[j]]))
2062 isl_assert(tab->mat->ctx, j < n_extra, goto error);
2063 isl_tab_pivot(tab, row, extra[j]);
2064 extra[j] = extra[--n_extra];
2076 static int perform_undo(struct isl_tab *tab, struct isl_tab_undo *undo)
2078 switch (undo->type) {
2079 case isl_tab_undo_empty:
2082 case isl_tab_undo_nonneg:
2083 case isl_tab_undo_redundant:
2084 case isl_tab_undo_zero:
2085 case isl_tab_undo_allocate:
2086 case isl_tab_undo_relax:
2087 perform_undo_var(tab, undo);
2089 case isl_tab_undo_bset_eq:
2090 isl_basic_set_free_equality(tab->bset, 1);
2092 case isl_tab_undo_bset_ineq:
2093 isl_basic_set_free_inequality(tab->bset, 1);
2095 case isl_tab_undo_bset_div:
2096 isl_basic_set_free_div(tab->bset, 1);
2098 case isl_tab_undo_saved_basis:
2099 if (restore_basis(tab, undo->u.col_var) < 0)
2103 isl_assert(tab->mat->ctx, 0, return -1);
2108 /* Return the tableau to the state it was in when the snapshot "snap"
2111 int isl_tab_rollback(struct isl_tab *tab, struct isl_tab_undo *snap)
2113 struct isl_tab_undo *undo, *next;
2119 for (undo = tab->top; undo && undo != &tab->bottom; undo = next) {
2123 if (perform_undo(tab, undo) < 0) {
2137 /* The given row "row" represents an inequality violated by all
2138 * points in the tableau. Check for some special cases of such
2139 * separating constraints.
2140 * In particular, if the row has been reduced to the constant -1,
2141 * then we know the inequality is adjacent (but opposite) to
2142 * an equality in the tableau.
2143 * If the row has been reduced to r = -1 -r', with r' an inequality
2144 * of the tableau, then the inequality is adjacent (but opposite)
2145 * to the inequality r'.
2147 static enum isl_ineq_type separation_type(struct isl_tab *tab, unsigned row)
2150 unsigned off = 2 + tab->M;
2153 return isl_ineq_separate;
2155 if (!isl_int_is_one(tab->mat->row[row][0]))
2156 return isl_ineq_separate;
2157 if (!isl_int_is_negone(tab->mat->row[row][1]))
2158 return isl_ineq_separate;
2160 pos = isl_seq_first_non_zero(tab->mat->row[row] + off + tab->n_dead,
2161 tab->n_col - tab->n_dead);
2163 return isl_ineq_adj_eq;
2165 if (!isl_int_is_negone(tab->mat->row[row][off + tab->n_dead + pos]))
2166 return isl_ineq_separate;
2168 pos = isl_seq_first_non_zero(
2169 tab->mat->row[row] + off + tab->n_dead + pos + 1,
2170 tab->n_col - tab->n_dead - pos - 1);
2172 return pos == -1 ? isl_ineq_adj_ineq : isl_ineq_separate;
2175 /* Check the effect of inequality "ineq" on the tableau "tab".
2177 * isl_ineq_redundant: satisfied by all points in the tableau
2178 * isl_ineq_separate: satisfied by no point in the tableau
2179 * isl_ineq_cut: satisfied by some by not all points
2180 * isl_ineq_adj_eq: adjacent to an equality
2181 * isl_ineq_adj_ineq: adjacent to an inequality.
2183 enum isl_ineq_type isl_tab_ineq_type(struct isl_tab *tab, isl_int *ineq)
2185 enum isl_ineq_type type = isl_ineq_error;
2186 struct isl_tab_undo *snap = NULL;
2191 return isl_ineq_error;
2193 if (isl_tab_extend_cons(tab, 1) < 0)
2194 return isl_ineq_error;
2196 snap = isl_tab_snap(tab);
2198 con = isl_tab_add_row(tab, ineq);
2202 row = tab->con[con].index;
2203 if (isl_tab_row_is_redundant(tab, row))
2204 type = isl_ineq_redundant;
2205 else if (isl_int_is_neg(tab->mat->row[row][1]) &&
2207 isl_int_abs_ge(tab->mat->row[row][1],
2208 tab->mat->row[row][0]))) {
2209 if (at_least_zero(tab, &tab->con[con]))
2210 type = isl_ineq_cut;
2212 type = separation_type(tab, row);
2213 } else if (tab->rational ? (sign_of_min(tab, &tab->con[con]) < 0)
2214 : isl_tab_min_at_most_neg_one(tab, &tab->con[con]))
2215 type = isl_ineq_cut;
2217 type = isl_ineq_redundant;
2219 if (isl_tab_rollback(tab, snap))
2220 return isl_ineq_error;
2223 isl_tab_rollback(tab, snap);
2224 return isl_ineq_error;
2227 void isl_tab_dump(struct isl_tab *tab, FILE *out, int indent)
2233 fprintf(out, "%*snull tab\n", indent, "");
2236 fprintf(out, "%*sn_redundant: %d, n_dead: %d", indent, "",
2237 tab->n_redundant, tab->n_dead);
2239 fprintf(out, ", rational");
2241 fprintf(out, ", empty");
2243 fprintf(out, "%*s[", indent, "");
2244 for (i = 0; i < tab->n_var; ++i) {
2246 fprintf(out, (i == tab->n_param ||
2247 i == tab->n_var - tab->n_div) ? "; "
2249 fprintf(out, "%c%d%s", tab->var[i].is_row ? 'r' : 'c',
2251 tab->var[i].is_zero ? " [=0]" :
2252 tab->var[i].is_redundant ? " [R]" : "");
2254 fprintf(out, "]\n");
2255 fprintf(out, "%*s[", indent, "");
2256 for (i = 0; i < tab->n_con; ++i) {
2259 fprintf(out, "%c%d%s", tab->con[i].is_row ? 'r' : 'c',
2261 tab->con[i].is_zero ? " [=0]" :
2262 tab->con[i].is_redundant ? " [R]" : "");
2264 fprintf(out, "]\n");
2265 fprintf(out, "%*s[", indent, "");
2266 for (i = 0; i < tab->n_row; ++i) {
2267 const char *sign = "";
2270 if (tab->row_sign) {
2271 if (tab->row_sign[i] == isl_tab_row_unknown)
2273 else if (tab->row_sign[i] == isl_tab_row_neg)
2275 else if (tab->row_sign[i] == isl_tab_row_pos)
2280 fprintf(out, "r%d: %d%s%s", i, tab->row_var[i],
2281 isl_tab_var_from_row(tab, i)->is_nonneg ? " [>=0]" : "", sign);
2283 fprintf(out, "]\n");
2284 fprintf(out, "%*s[", indent, "");
2285 for (i = 0; i < tab->n_col; ++i) {
2288 fprintf(out, "c%d: %d%s", i, tab->col_var[i],
2289 var_from_col(tab, i)->is_nonneg ? " [>=0]" : "");
2291 fprintf(out, "]\n");
2292 r = tab->mat->n_row;
2293 tab->mat->n_row = tab->n_row;
2294 c = tab->mat->n_col;
2295 tab->mat->n_col = 2 + tab->M + tab->n_col;
2296 isl_mat_dump(tab->mat, out, indent);
2297 tab->mat->n_row = r;
2298 tab->mat->n_col = c;
2300 isl_basic_set_dump(tab->bset, out, indent);