remove obviously redundant divs based on inequalities

diff --git a/include/isl_int.h b/include/isl_int.h
index 27ddc65..4164170 100644 (file)
--- a/include/isl_int.h
+++ b/include/isl_int.h
@@ -58,6 +58,7 @@ typedef mpz_t isl_int;
 #define isl_int_abs_eq(i,j)    (mpz_cmpabs(i,j) == 0)
 #define isl_int_abs_ne(i,j)    (mpz_cmpabs(i,j) != 0)
 #define isl_int_abs_lt(i,j)    (mpz_cmpabs(i,j) < 0)
+#define isl_int_abs_gt(i,j)    (mpz_cmpabs(i,j) > 0)
 
 
 #define isl_int_is_zero(i)     (isl_int_sgn(i) == 0)

diff --git a/isl_map.c b/isl_map.c
index fc001e9..61f2277 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -1003,7 +1003,9 @@ out:
        return bmap;
 }
 
-static struct isl_basic_map *eliminate_divs(
+/* Elimininate divs based on equalities
+ */
+static struct isl_basic_map *eliminate_divs_eq(
                struct isl_ctx *ctx, struct isl_basic_map *bmap,
                int *progress)
 {
@@ -1026,10 +1028,11 @@ static struct isl_basic_map *eliminate_divs(
                        *progress = 1;
                        eliminate_div(ctx, bmap, bmap->eq[i], d);
                        isl_basic_map_drop_equality(ctx, bmap, i);
+                       break;
                }
        }
        if (modified)
-               return eliminate_divs(ctx, bmap, progress);
+               return eliminate_divs_eq(ctx, bmap, progress);
        return bmap;
 }
 
@@ -1080,6 +1083,129 @@ static struct isl_basic_map *normalize_constraints(
        return bmap;
 }
 
+
+/* Eliminate the specified variables from the constraints using
+ * Fourier-Motzkin.  The variables themselves are not removed.
+ */
+struct isl_basic_map *isl_basic_map_eliminate_vars(struct isl_ctx *ctx,
+       struct isl_basic_map *bmap, int pos, unsigned n)
+{
+       int d;
+       int i, j, k;
+       unsigned total;
+       unsigned extra;
+
+       if (!bmap)
+               return NULL;
+       total = bmap->nparam + bmap->n_in + bmap->n_out + bmap->n_div;
+       extra = bmap->extra - bmap->n_div;
+
+       bmap = isl_basic_map_cow(ctx, bmap);
+       bmap = isl_basic_map_gauss(ctx, bmap, NULL);
+       for (d = pos + n - 1; d >= pos; --d) {
+               int n_lower, n_upper;
+               if (!bmap)
+                       return NULL;
+               for (i = 0; i < bmap->n_eq; ++i) {
+                       if (isl_int_is_zero(bmap->eq[i][1+d]))
+                               continue;
+                       isl_basic_map_drop_equality(ctx, bmap, i);
+                       break;
+               }
+               if (i < bmap->n_eq)
+                       continue;
+               n_lower = 0;
+               n_upper = 0;
+               for (i = 0; i < bmap->n_ineq; ++i) {
+                       if (isl_int_is_pos(bmap->ineq[i][1+d]))
+                               n_lower++;
+                       else if (isl_int_is_neg(bmap->ineq[i][1+d]))
+                               n_upper++;
+               }
+               bmap = isl_basic_map_extend(ctx, bmap,
+                               bmap->nparam, bmap->n_in, bmap->n_out, 0,
+                               0, n_lower * n_upper);
+               for (i = bmap->n_ineq - 1; i >= 0; --i) {
+                       int last;
+                       if (isl_int_is_zero(bmap->ineq[i][1+d]))
+                               continue;
+                       last = -1;
+                       for (j = 0; j < i; ++j) {
+                               if (isl_int_is_zero(bmap->ineq[j][1+d]))
+                                       continue;
+                               last = j;
+                               if (isl_int_sgn(bmap->ineq[i][1+d]) ==
+                                   isl_int_sgn(bmap->ineq[j][1+d]))
+                                       continue;
+                               k = isl_basic_map_alloc_inequality(ctx, bmap);
+                               if (k < 0)
+                                       goto error;
+                               isl_seq_cpy(bmap->ineq[k], bmap->ineq[i],
+                                               1+total);
+                               isl_seq_clr(bmap->ineq[k]+1+total, extra);
+                               isl_seq_elim(bmap->ineq[k], bmap->ineq[j],
+                                               1+d, 1+total, NULL);
+                       }
+                       isl_basic_map_drop_inequality(ctx, bmap, i);
+                       i = last + 1;
+               }
+               if (n_lower > 0 && n_upper > 0) {
+                       bmap = normalize_constraints(ctx, bmap);
+                       bmap = isl_basic_map_gauss(ctx, bmap, NULL);
+                       if (F_ISSET(bmap, ISL_BASIC_MAP_EMPTY))
+                               break;
+               }
+       }
+       return bmap;
+error:
+       isl_basic_map_free(ctx, bmap);
+       return NULL;
+}
+
+struct isl_basic_set *isl_basic_set_eliminate_vars(struct isl_ctx *ctx,
+       struct isl_basic_set *bset, unsigned pos, unsigned n)
+{
+       return (struct isl_basic_set *)isl_basic_map_eliminate_vars(ctx,
+                       (struct isl_basic_map *)bset, pos, n);
+}
+
+/* Elimininate divs based on inequalities
+ */
+static struct isl_basic_map *eliminate_divs_ineq(
+               struct isl_ctx *ctx, struct isl_basic_map *bmap,
+               int *progress)
+{
+       int d;
+       int i;
+       unsigned off;
+
+       if (!bmap)
+               return NULL;
+
+       off = 1 + bmap->nparam + bmap->n_in + bmap->n_out;
+
+       for (d = bmap->n_div - 1; d >= 0 ; --d) {
+               for (i = 0; i < bmap->n_eq; ++i)
+                       if (!isl_int_is_zero(bmap->eq[i][off + d]))
+                               break;
+               if (i < bmap->n_eq)
+                       continue;
+               for (i = 0; i < bmap->n_ineq; ++i)
+                       if (isl_int_abs_gt(bmap->ineq[i][off + d], ctx->one))
+                               break;
+               if (i < bmap->n_ineq)
+                       continue;
+               *progress = 1;
+               bmap = isl_basic_map_eliminate_vars(ctx, bmap, (off-1)+d, 1);
+               if (F_ISSET(bmap, ISL_BASIC_MAP_EMPTY))
+                       break;
+               bmap = isl_basic_map_drop_div(ctx, bmap, d);
+               if (!bmap)
+                       break;
+       }
+       return bmap;
+}
+
 struct isl_basic_map *isl_basic_map_simplify(
                struct isl_ctx *ctx, struct isl_basic_map *bmap)
 {
@@ -1089,7 +1215,8 @@ struct isl_basic_map *isl_basic_map_simplify(
        while (progress) {
                progress = 0;
                bmap = normalize_constraints(ctx, bmap);
-               bmap = eliminate_divs(ctx, bmap, &progress);
+               bmap = eliminate_divs_eq(ctx, bmap, &progress);
+               bmap = eliminate_divs_ineq(ctx, bmap, &progress);
                bmap = isl_basic_map_gauss(ctx, bmap, &progress);
                bmap = remove_duplicate_divs(ctx, bmap, &progress);
                bmap = remove_duplicate_constraints(ctx, bmap, &progress);

diff --git a/isl_map_private.h b/isl_map_private.h
index 7f980e0..22411d5 100644 (file)
--- a/isl_map_private.h
+++ b/isl_map_private.h
@@ -53,3 +53,6 @@ struct isl_map *isl_map_remove_empty_parts(struct isl_ctx *ctx,
        struct isl_map *map);
 struct isl_set *isl_set_remove_empty_parts(struct isl_ctx *ctx,
        struct isl_set *set);
+
+struct isl_basic_set *isl_basic_set_eliminate_vars(struct isl_ctx *ctx,
+       struct isl_basic_set *bset, unsigned pos, unsigned n);