isl_scan.c

   1 #include "isl_basis_reduction.h"
   2 #include "isl_scan.h"
   3 #include "isl_seq.h"
   4 #include "isl_tab.h"
   5
   6 /* Call callback->add with the current sample value of the tableau "tab".
   7  */
   8 static int add_solution(struct isl_tab *tab, struct isl_scan_callback *callback)
   9 {
  10         struct isl_vec *sample;
  11
  12         if (!tab)
  13                 return -1;
  14         sample = isl_tab_get_sample_value(tab);
  15         if (!sample)
  16                 return -1;
  17
  18         return callback->add(callback, sample);
  19 }
  20
  21 static int scan_0D(struct isl_basic_set *bset,
  22         struct isl_scan_callback *callback)
  23 {
  24         struct isl_vec *sample;
  25
  26         sample = isl_vec_alloc(bset->ctx, 1);
  27         isl_basic_set_free(bset);
  28
  29         if (!sample)
  30                 return -1;
  31
  32         isl_int_set_si(sample->el[0], 1);
  33
  34         return callback->add(callback, sample);
  35 }
  36
  37 /* Look for all integer points in "bset", which is assumed to be unbounded,
  38  * and call callback->add on each of them.
  39  *
  40  * We first compute a reduced basis for the set and then scan
  41  * the set in the directions of this basis.
  42  * We basically perform a depth first search, where in each level i
  43  * we compute the range in the i-th basis vector direction, given
  44  * fixed values in the directions of the previous basis vector.
  45  * We then add an equality to the tableau fixing the value in the
  46  * direction of the current basis vector to each value in the range
  47  * in turn and then continue to the next level.
  48  *
  49  * The search is implemented iteratively.  "level" identifies the current
  50  * basis vector.  "init" is true if we want the first value at the current
  51  * level and false if we want the next value.
  52  * Solutions are added in the leaves of the search tree, i.e., after
  53  * we have fixed a value in each direction of the basis.
  54  */
  55 int isl_basic_set_scan(struct isl_basic_set *bset,
  56         struct isl_scan_callback *callback)
  57 {
  58         unsigned dim;
  59         struct isl_mat *B = NULL;
  60         struct isl_tab *tab = NULL;
  61         struct isl_vec *min;
  62         struct isl_vec *max;
  63         struct isl_tab_undo **snap;
  64         int level;
  65         int init;
  66         enum isl_lp_result res;
  67
  68         if (!bset)
  69                 return -1;
  70
  71         dim = isl_basic_set_total_dim(bset);
  72         if (dim == 0)
  73                 return scan_0D(bset, callback);
  74
  75         min = isl_vec_alloc(bset->ctx, dim);
  76         max = isl_vec_alloc(bset->ctx, dim);
  77         snap = isl_alloc_array(bset->ctx, struct isl_tab_undo *, dim);
  78
  79         if (!min || !max || !snap)
  80                 goto error;
  81
  82         tab = isl_tab_from_basic_set(bset);
  83         if (!tab)
  84                 goto error;
  85
  86         tab->basis = isl_mat_identity(bset->ctx, 1 + dim);
  87         if (1)
  88                 tab = isl_tab_compute_reduced_basis(tab);
  89         if (!tab)
  90                 goto error;
  91         B = isl_mat_copy(tab->basis);
  92         if (!B)
  93                 goto error;
  94
  95         level = 0;
  96         init = 1;
  97
  98         while (level >= 0) {
  99                 int empty = 0;
 100                 if (init) {
 101                         res = isl_tab_min(tab, B->row[1 + level],
 102                                     bset->ctx->one, &min->el[level], NULL, 0);
 103                         if (res == isl_lp_empty)
 104                                 empty = 1;
 105                         if (res == isl_lp_error || res == isl_lp_unbounded)
 106                                 goto error;
 107                         isl_seq_neg(B->row[1 + level] + 1,
 108                                     B->row[1 + level] + 1, dim);
 109                         res = isl_tab_min(tab, B->row[1 + level],
 110                                     bset->ctx->one, &max->el[level], NULL, 0);
 111                         isl_seq_neg(B->row[1 + level] + 1,
 112                                     B->row[1 + level] + 1, dim);
 113                         isl_int_neg(max->el[level], max->el[level]);
 114                         if (res == isl_lp_empty)
 115                                 empty = 1;
 116                         if (res == isl_lp_error || res == isl_lp_unbounded)
 117                                 goto error;
 118                         snap[level] = isl_tab_snap(tab);
 119                 } else
 120                         isl_int_add_ui(min->el[level], min->el[level], 1);
 121
 122                 if (empty || isl_int_gt(min->el[level], max->el[level])) {
 123                         level--;
 124                         init = 0;
 125                         if (level >= 0)
 126                                 if (isl_tab_rollback(tab, snap[level]) < 0)
 127                                         goto error;
 128                         continue;
 129                 }
 130                 isl_int_neg(B->row[1 + level][0], min->el[level]);
 131                 tab = isl_tab_add_valid_eq(tab, B->row[1 + level]);
 132                 isl_int_set_si(B->row[1 + level][0], 0);
 133                 if (level < dim - 1) {
 134                         ++level;
 135                         init = 1;
 136                         continue;
 137                 }
 138                 if (add_solution(tab, callback) < 0)
 139                         goto error;
 140                 init = 0;
 141                 if (isl_tab_rollback(tab, snap[level]) < 0)
 142                         goto error;
 143         }
 144
 145         isl_tab_free(tab);
 146         free(snap);
 147         isl_vec_free(min);
 148         isl_vec_free(max);
 149         isl_basic_set_free(bset);
 150         isl_mat_free(B);
 151         return 0;
 152 error:
 153         isl_tab_free(tab);
 154         free(snap);
 155         isl_vec_free(min);
 156         isl_vec_free(max);
 157         isl_basic_set_free(bset);
 158         isl_mat_free(B);
 159         return -1;
 160 }