isl_basic_set_compare_at: compute result in terms of maximal (integral) difference

Computing the maximal instead of the minimal difference will allow
us to reuse much of the code in isl_basic_set_follows_at later.
Since we only need the sign of the optimum, we don't really need
the exact value.

diff --git a/isl_map.c b/isl_map.c
index 7c50463..8a97475 100644 (file)
--- a/isl_map.c
+++ b/isl_map.c
@@ -4676,7 +4676,7 @@ int isl_basic_set_compare_at(struct isl_basic_set *bset1,
        unsigned total;
        unsigned nparam;
        unsigned dim1, dim2;
-       isl_int num, den;
+       isl_int opt;
        enum isl_lp_result res;
        int cmp;
 
@@ -4707,21 +4707,19 @@ int isl_basic_set_compare_at(struct isl_basic_set *bset1,
        isl_int_set_si(obj->block.data[1+nparam+pos+(dim1-pos)], -1);
        if (!obj)
                goto error;
-       isl_int_init(num);
-       isl_int_init(den);
-       res = isl_basic_map_solve_lp(bmap1, 0, obj->block.data, ctx->one,
-                                       &num, &den, NULL);
+       isl_int_init(opt);
+       res = isl_basic_map_solve_lp(bmap1, 1, obj->block.data, ctx->one,
+                                       &opt, NULL, NULL);
        if (res == isl_lp_empty)
                cmp = 0;
-       else if (res == isl_lp_ok && isl_int_is_pos(num))
-               cmp = 1;
-       else if ((res == isl_lp_ok && isl_int_is_neg(num)) ||
+       else if ((res == isl_lp_ok && isl_int_is_pos(opt)) ||
                  res == isl_lp_unbounded)
+               cmp = 1;
+       else if (res == isl_lp_ok && isl_int_is_neg(opt))
                cmp = -1;
        else
                cmp = -2;
-       isl_int_clear(num);
-       isl_int_clear(den);
+       isl_int_clear(opt);
        isl_basic_map_free(bmap1);
        isl_vec_free(obj);
        return cmp;