isl_scan.c

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/*
 * Copyright 2008-2009 Katholieke Universiteit Leuven
 *
 * Use of this software is governed by the MIT license
 *
 * Written by Sven Verdoolaege, K.U.Leuven, Departement
 * Computerwetenschappen, Celestijnenlaan 200A, B-3001 Leuven, Belgium
 */
 
#include <isl_ctx_private.h>
#include <isl_map_private.h>
#include "isl_basis_reduction.h"
#include "isl_scan.h"
#include <isl_seq.h>
#include "isl_tab.h"
#include <isl_val_private.h>
#include <isl_vec_private.h>
 
struct isl_counter {
  struct isl_scan_callback callback;
  isl_int count;
  isl_int max;
};
 
static isl_stat increment_counter(struct isl_scan_callback *cb,
  __isl_take isl_vec *sample)
{
  struct isl_counter *cnt = (struct isl_counter *)cb;
 
  isl_int_add_ui(cnt->count, cnt->count, 1);
 
  isl_vec_free(sample);
 
  if (isl_int_is_zero(cnt->max) || isl_int_lt(cnt->count, cnt->max))
    return isl_stat_ok;
  return isl_stat_error;
}
 
static int increment_range(struct isl_scan_callback *cb, isl_int min, isl_int max)
{
  struct isl_counter *cnt = (struct isl_counter *)cb;
 
  isl_int_add(cnt->count, cnt->count, max);
  isl_int_sub(cnt->count, cnt->count, min);
  isl_int_add_ui(cnt->count, cnt->count, 1);
 
  if (isl_int_is_zero(cnt->max) || isl_int_lt(cnt->count, cnt->max))
    return 0;
  isl_int_set(cnt->count, cnt->max);
  return -1;
}
 
/* Call callback->add with the current sample value of the tableau "tab".
 */
static int add_solution(struct isl_tab *tab, struct isl_scan_callback *callback)
{
  struct isl_vec *sample;
 
  if (!tab)
    return -1;
  sample = isl_tab_get_sample_value(tab);
  if (!sample)
    return -1;
 
  return callback->add(callback, sample);
}
 
static isl_stat scan_0D(__isl_take isl_basic_set *bset,
  struct isl_scan_callback *callback)
{
  struct isl_vec *sample;
 
  sample = isl_vec_alloc(bset->ctx, 1);
  isl_basic_set_free(bset);
 
  if (!sample)
    return isl_stat_error;
 
  isl_int_set_si(sample->el[0], 1);
 
  return callback->add(callback, sample);
}
 
/* Look for all integer points in "bset", which is assumed to be bounded,
 * and call callback->add on each of them.
 *
 * We first compute a reduced basis for the set and then scan
 * the set in the directions of this basis.
 * We basically perform a depth first search, where in each level i
 * we compute the range in the i-th basis vector direction, given
 * fixed values in the directions of the previous basis vector.
 * We then add an equality to the tableau fixing the value in the
 * direction of the current basis vector to each value in the range
 * in turn and then continue to the next level.
 *
 * The search is implemented iteratively.  "level" identifies the current
 * basis vector.  "init" is true if we want the first value at the current
 * level and false if we want the next value.
 * Solutions are added in the leaves of the search tree, i.e., after
 * we have fixed a value in each direction of the basis.
 */
isl_stat isl_basic_set_scan(__isl_take isl_basic_set *bset,
  struct isl_scan_callback *callback)
{
  isl_size dim;
  struct isl_mat *B = NULL;
  struct isl_tab *tab = NULL;
  struct isl_vec *min;
  struct isl_vec *max;
  struct isl_tab_undo **snap;
  int level;
  int init;
  enum isl_lp_result res;
 
  dim = isl_basic_set_dim(bset, isl_dim_all);
  if (dim < 0) {
    bset = isl_basic_set_free(bset);
    return isl_stat_error;
  }
 
  if (dim == 0)
    return scan_0D(bset, callback);
 
  min = isl_vec_alloc(bset->ctx, dim);
  max = isl_vec_alloc(bset->ctx, dim);
  snap = isl_alloc_array(bset->ctx, struct isl_tab_undo *, dim);
 
  if (!min || !max || !snap)
    goto error;
 
  tab = isl_tab_from_basic_set(bset, 0);
  if (!tab)
    goto error;
  if (isl_tab_extend_cons(tab, dim + 1) < 0)
    goto error;
 
  tab->basis = isl_mat_identity(bset->ctx, 1 + dim);
  if (1)
    tab = isl_tab_compute_reduced_basis(tab);
  if (!tab)
    goto error;
  B = isl_mat_copy(tab->basis);
  if (!B)
    goto error;
 
  level = 0;
  init = 1;
 
  while (level >= 0) {
    int empty = 0;
    if (init) {
      res = isl_tab_min(tab, B->row[1 + level],
            bset->ctx->one, &min->el[level], NULL, 0);
      if (res == isl_lp_empty)
        empty = 1;
      if (res == isl_lp_error || res == isl_lp_unbounded)
        goto error;
      isl_seq_neg(B->row[1 + level] + 1,
            B->row[1 + level] + 1, dim);
      res = isl_tab_min(tab, B->row[1 + level],
            bset->ctx->one, &max->el[level], NULL, 0);
      isl_seq_neg(B->row[1 + level] + 1,
            B->row[1 + level] + 1, dim);
      isl_int_neg(max->el[level], max->el[level]);
      if (res == isl_lp_empty)
        empty = 1;
      if (res == isl_lp_error || res == isl_lp_unbounded)
        goto error;
      snap[level] = isl_tab_snap(tab);
    } else
      isl_int_add_ui(min->el[level], min->el[level], 1);
 
    if (empty || isl_int_gt(min->el[level], max->el[level])) {
      level--;
      init = 0;
      if (level >= 0)
        if (isl_tab_rollback(tab, snap[level]) < 0)
          goto error;
      continue;
    }
    if (level == dim - 1 && callback->add == increment_counter) {
      if (increment_range(callback,
              min->el[level], max->el[level]))
        goto error;
      level--;
      init = 0;
      if (level >= 0)
        if (isl_tab_rollback(tab, snap[level]) < 0)
          goto error;
      continue;
    }
    isl_int_neg(B->row[1 + level][0], min->el[level]);
    if (isl_tab_add_valid_eq(tab, B->row[1 + level]) < 0)
      goto error;
    isl_int_set_si(B->row[1 + level][0], 0);
    if (level < dim - 1) {
      ++level;
      init = 1;
      continue;
    }
    if (add_solution(tab, callback) < 0)
      goto error;
    init = 0;
    if (isl_tab_rollback(tab, snap[level]) < 0)
      goto error;
  }
 
  isl_tab_free(tab);
  free(snap);
  isl_vec_free(min);
  isl_vec_free(max);
  isl_basic_set_free(bset);
  isl_mat_free(B);
  return isl_stat_ok;
error:
  isl_tab_free(tab);
  free(snap);
  isl_vec_free(min);
  isl_vec_free(max);
  isl_basic_set_free(bset);
  isl_mat_free(B);
  return isl_stat_error;
}
 
isl_stat isl_set_scan(__isl_take isl_set *set,
  struct isl_scan_callback *callback)
{
  int i;
 
  if (!set || !callback)
    goto error;
 
  set = isl_set_cow(set);
  set = isl_set_make_disjoint(set);
  set = isl_set_compute_divs(set);
  if (!set)
    goto error;
 
  for (i = 0; i < set->n; ++i)
    if (isl_basic_set_scan(isl_basic_set_copy(set->p[i]),
          callback) < 0)
      goto error;
 
  isl_set_free(set);
  return isl_stat_ok;
error:
  isl_set_free(set);
  return isl_stat_error;
}
 
int isl_basic_set_count_upto(__isl_keep isl_basic_set *bset,
  isl_int max, isl_int *count)
{
  struct isl_counter cnt = { { &increment_counter } };
 
  if (!bset)
    return -1;
 
  isl_int_init(cnt.count);
  isl_int_init(cnt.max);
 
  isl_int_set_si(cnt.count, 0);
  isl_int_set(cnt.max, max);
  if (isl_basic_set_scan(isl_basic_set_copy(bset), &cnt.callback) < 0 &&
      isl_int_lt(cnt.count, cnt.max))
    goto error;
 
  isl_int_set(*count, cnt.count);
  isl_int_clear(cnt.max);
  isl_int_clear(cnt.count);
 
  return 0;
error:
  isl_int_clear(cnt.count);
  return -1;
}
 
int isl_set_count_upto(__isl_keep isl_set *set, isl_int max, isl_int *count)
{
  struct isl_counter cnt = { { &increment_counter } };
 
  if (!set)
    return -1;
 
  isl_int_init(cnt.count);
  isl_int_init(cnt.max);
 
  isl_int_set_si(cnt.count, 0);
  isl_int_set(cnt.max, max);
  if (isl_set_scan(isl_set_copy(set), &cnt.callback) < 0 &&
      isl_int_lt(cnt.count, cnt.max))
    goto error;
 
  isl_int_set(*count, cnt.count);
  isl_int_clear(cnt.max);
  isl_int_clear(cnt.count);
 
  return 0;
error:
  isl_int_clear(cnt.count);
  return -1;
}
 
int isl_set_count(__isl_keep isl_set *set, isl_int *count)
{
  if (!set)
    return -1;
  return isl_set_count_upto(set, set->ctx->zero, count);
}
 
/* Count the total number of elements in "set" (in an inefficient way) and
 * return the result.
 */
__isl_give isl_val *isl_set_count_val(__isl_keep isl_set *set)
{
  isl_val *v;
 
  if (!set)
    return NULL;
  v = isl_val_zero(isl_set_get_ctx(set));
  v = isl_val_cow(v);
  if (!v)
    return NULL;
  if (isl_set_count(set, &v->n) < 0)
    v = isl_val_free(v);
  return v;
}