isl_basic_map_affine_hull: fix search for integer points

Before, we would mistakenly only look for integer points
in adjacent hyperplanes.  This would be sufficient if we
were looking instead for rational points, although we could
then obtain an over-approximation of the integer affine hull.

diff --git a/isl_affine_hull.c b/isl_affine_hull.c
index ef37303..323255d 100644 (file)
--- a/isl_affine_hull.c
+++ b/isl_affine_hull.c
@@ -255,6 +255,13 @@ error:
        return NULL;
 }
 
+/* Find an integer point in "bset" that lies outside of the equality
+ * "eq" e(x) = 0.
+ * If "up" is true, look for a point satisfying e(x) - 1 >= 0.
+ * Otherwise, look for a point satisfying -e(x) - 1 >= 0 (i.e., e(x) <= -1).
+ * The point, if found, is returned as a singleton set.
+ * If no point can be found, the empty set is returned.
+ */
 static struct isl_basic_set *outside_point(struct isl_ctx *ctx,
        struct isl_basic_set *bset, isl_int *eq, int up)
 {
@@ -268,15 +275,15 @@ static struct isl_basic_set *outside_point(struct isl_ctx *ctx,
        if (!slice)
                goto error;
        dim = isl_basic_set_n_dim(slice);
-       slice = isl_basic_set_extend(slice, 0, dim, 0, 1, 0);
-       k = isl_basic_set_alloc_equality(slice);
+       slice = isl_basic_set_extend(slice, 0, dim, 0, 0, 1);
+       k = isl_basic_set_alloc_inequality(slice);
        if (k < 0)
                goto error;
-       isl_seq_cpy(slice->eq[k], eq, 1 + dim);
        if (up)
-               isl_int_add_ui(slice->eq[k][0], slice->eq[k][0], 1);
+               isl_seq_cpy(slice->ineq[k], eq, 1 + dim);
        else
-               isl_int_sub_ui(slice->eq[k][0], slice->eq[k][0], 1);
+               isl_seq_neg(slice->ineq[k], eq, 1 + dim);
+       isl_int_sub_ui(slice->ineq[k][0], slice->ineq[k][0], 1);
 
        sample = isl_basic_set_sample(slice);
        if (!sample)

diff --git a/isl_test.c b/isl_test.c
index 37510f7..b13e294 100644 (file)
--- a/isl_test.c
+++ b/isl_test.c
@@ -412,6 +412,7 @@ void test_affine_hull(struct isl_ctx *ctx)
 {
        test_affine_hull_case(ctx, "affine2");
        test_affine_hull_case(ctx, "affine");
+       test_affine_hull_case(ctx, "affine3");
 }
 
 void test_convex_hull_case(struct isl_ctx *ctx, const char *name)

diff --git a/test_inputs/affine3.polylib b/test_inputs/affine3.polylib
new file mode 100644 (file)
index 0000000..f2bc9a2
--- /dev/null
+++ b/test_inputs/affine3.polylib
@@ -0,0 +1,7 @@
+3 4
+1 1 0 0
+1 -7 4 2
+1 5 -4 2
+
+1 4
+0 3 -2 0