isl_basic_set_sample: only perform basis reduction once

On larger problem, much time was spent on repeated basis reductions
with little or no reduction on the number of points visited.
The initial basis reduction seems to be sufficient in most cases.

diff --git a/include/isl_ctx.h.in b/include/isl_ctx.h.in
index ef16c06..9168ff3 100644 (file)
--- a/include/isl_ctx.h.in
+++ b/include/isl_ctx.h.in
@@ -69,6 +69,10 @@ struct isl_ctx {
        #define                 ISL_PIP_PIP     1
        unsigned                pip;
 
+       #define                 ISL_GBR_NEVER   0
+       #define                 ISL_GBR_ONCE    1
+       #define                 ISL_GBR_ALWAYS  2
+       unsigned                gbr;
        unsigned                gbr_only_first;
 };
 

diff --git a/isl_ctx.c b/isl_ctx.c
index 2922a46..bee266b 100644 (file)
--- a/isl_ctx.c
+++ b/isl_ctx.c
@@ -37,6 +37,9 @@ struct isl_ctx *isl_ctx_alloc()
        ctx->ilp_solver = ISL_ILP_GBR;
        ctx->pip = ISL_PIP_TAB;
 
+       ctx->gbr = ISL_GBR_ONCE;
+       ctx->gbr_only_first = 0;
+
        return ctx;
 error:
        free(ctx);

diff --git a/isl_sample.c b/isl_sample.c
index 51eea13..669ce0c 100644 (file)
--- a/isl_sample.c
+++ b/isl_sample.c
@@ -328,7 +328,7 @@ static struct isl_basic_set *basic_set_reduced(struct isl_basic_set *bset,
                return NULL;
 
        gbr_only_first = bset->ctx->gbr_only_first;
-       bset->ctx->gbr_only_first = 1;
+       bset->ctx->gbr_only_first = bset->ctx->gbr == ISL_GBR_ONCE;
        *T = isl_basic_set_reduced_basis(bset);
        bset->ctx->gbr_only_first = gbr_only_first;
 
@@ -418,6 +418,8 @@ error:
 static struct isl_vec *sample_bounded(struct isl_basic_set *bset)
 {
        unsigned dim;
+       unsigned gbr;
+       struct isl_ctx *ctx;
        struct isl_vec *sample;
        struct isl_vec *obj = NULL;
        struct isl_mat *T = NULL;
@@ -438,6 +440,9 @@ static struct isl_vec *sample_bounded(struct isl_basic_set *bset)
        if (bset->n_eq > 0)
                return sample_eq(bset, sample_bounded);
 
+       ctx = bset->ctx;
+       gbr = ctx->gbr;
+
        isl_int_init(min);
        isl_int_init(max);
        obj = isl_vec_alloc(bset->ctx, 1 + dim);
@@ -460,7 +465,10 @@ static struct isl_vec *sample_bounded(struct isl_basic_set *bset)
                goto out;
        }
 
-       if (isl_int_ne(min, max)) {
+       if (ctx->gbr != ISL_GBR_NEVER && isl_int_ne(min, max)) {
+               if (ctx->gbr == ISL_GBR_ONCE)
+                       ctx->gbr = ISL_GBR_NEVER;
+
                bset = basic_set_reduced(bset, &T);
                if (!bset)
                        goto error;
@@ -491,8 +499,10 @@ out:
        isl_vec_free(obj);
        isl_int_clear(min);
        isl_int_clear(max);
+       ctx->gbr = gbr;
        return sample;
 error:
+       ctx->gbr = gbr;
        isl_mat_free(T);
        isl_basic_set_free(bset);
        isl_vec_free(obj);