isl_basic_map_eliminate_vars: ensure variable is eliminated before dropping equality

Before we would call isl_basic_map_gauss, but this is overkill
and it won't work if we eliminate variables that are not in the
final position.

diff --git a/isl_map.c b/isl_map.c
index b339455..f4132e7 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -905,6 +905,44 @@ static void swap_div(struct isl_basic_map *bmap, int a, int b)
                isl_int_swap(bmap->div[i][1+1+off+a], bmap->div[i][1+1+off+b]);
 }
 
+static void eliminate_var_using_equality(struct isl_basic_map *bmap,
+       unsigned pos, isl_int *eq, int *progress)
+{
+       unsigned total;
+       int k;
+
+       total = bmap->nparam + bmap->n_in + bmap->n_out + bmap->n_div;
+       for (k = 0; k < bmap->n_eq; ++k) {
+               if (bmap->eq[k] == eq)
+                       continue;
+               if (isl_int_is_zero(bmap->eq[k][1+pos]))
+                       continue;
+               if (progress)
+                       *progress = 1;
+               isl_seq_elim(bmap->eq[k], eq, 1+pos, 1+total, NULL);
+       }
+
+       for (k = 0; k < bmap->n_ineq; ++k) {
+               if (isl_int_is_zero(bmap->ineq[k][1+pos]))
+                       continue;
+               if (progress)
+                       *progress = 1;
+               isl_seq_elim(bmap->ineq[k], eq, 1+pos, 1+total, NULL);
+       }
+
+       for (k = 0; k < bmap->n_div; ++k) {
+               if (isl_int_is_zero(bmap->div[k][0]))
+                       continue;
+               if (isl_int_is_zero(bmap->div[k][1+1+pos]))
+                       continue;
+               if (progress)
+                       *progress = 1;
+               isl_seq_elim(bmap->div[k]+1, eq,
+                               1+pos, 1+total, &bmap->div[k][0]);
+       }
+}
+       
+
 struct isl_basic_map *isl_basic_map_gauss(
        struct isl_basic_map *bmap, int *progress)
 {
@@ -936,36 +974,8 @@ struct isl_basic_map *isl_basic_map_gauss(
                if (isl_int_is_neg(bmap->eq[done][1+last_var]))
                        isl_seq_neg(bmap->eq[done], bmap->eq[done], 1+total);
 
-               for (k = 0; k < bmap->n_eq; ++k) {
-                       if (k == done)
-                               continue;
-                       if (isl_int_is_zero(bmap->eq[k][1+last_var]))
-                               continue;
-                       if (progress)
-                               *progress = 1;
-                       isl_seq_elim(bmap->eq[k], bmap->eq[done],
-                                       1+last_var, 1+total, NULL);
-               }
-
-               for (k = 0; k < bmap->n_ineq; ++k) {
-                       if (isl_int_is_zero(bmap->ineq[k][1+last_var]))
-                               continue;
-                       if (progress)
-                               *progress = 1;
-                       isl_seq_elim(bmap->ineq[k], bmap->eq[done],
-                                       1+last_var, 1+total, NULL);
-               }
-
-               for (k = 0; k < bmap->n_div; ++k) {
-                       if (isl_int_is_zero(bmap->div[k][0]))
-                               continue;
-                       if (isl_int_is_zero(bmap->div[k][1+1+last_var]))
-                               continue;
-                       if (progress)
-                               *progress = 1;
-                       isl_seq_elim(bmap->div[k]+1, bmap->eq[done],
-                                       1+last_var, 1+total, &bmap->div[k][0]);
-               }
+               eliminate_var_using_equality(bmap, last_var, bmap->eq[done],
+                                               progress);
 
                if (last_var >= total_var &&
                    isl_int_is_zero(bmap->div[last_var - total_var][0])) {
@@ -1246,7 +1256,6 @@ struct isl_basic_map *isl_basic_map_eliminate_vars(
        extra = bmap->extra - bmap->n_div;
 
        bmap = isl_basic_map_cow(bmap);
-       bmap = isl_basic_map_gauss(bmap, NULL);
        for (d = pos + n - 1; d >= pos; --d) {
                int n_lower, n_upper;
                if (!bmap)
@@ -1254,6 +1263,7 @@ struct isl_basic_map *isl_basic_map_eliminate_vars(
                for (i = 0; i < bmap->n_eq; ++i) {
                        if (isl_int_is_zero(bmap->eq[i][1+d]))
                                continue;
+                       eliminate_var_using_equality(bmap, d, bmap->eq[i], NULL);
                        isl_basic_map_drop_equality(bmap, i);
                        break;
                }