From: Sven Verdoolaege <skimo@kotnet.org>
Date: Fri, 25 Sep 2009 17:17:20 +0000 (+0200)
Subject: isl_tab_basic_map_partial_lexopt: remove samples that are no longer useful
X-Git-Tag: isl-0.02~237
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=79d277b08490900bd698114586a63160a3da5d01;p=platform%2Fupstream%2Fisl.git

isl_tab_basic_map_partial_lexopt: remove samples that are no longer useful

When we test an inequality in row_sign, it is useful to store any
samples found, so we can use them to speed up the computation
of future row signs.
However, when we return from a branch, then all the samples found
since we entered the branch all satisfy the constraints on that
branch and so they will not satisfy the constraints on any other
branch.  We therefore save the current number of samples when
we enter a branch and then discard all subsequently added samples
when we return from the branch.
---

diff --git a/isl_tab.c b/isl_tab.c
index 94d3eb0..099a69e 100644
--- a/isl_tab.c
+++ b/isl_tab.c
@@ -183,6 +183,7 @@ void isl_tab_free(struct isl_tab *tab)
 	free(tab->col_var);
 	free(tab->row_sign);
 	isl_mat_free(tab->samples);
+	free(tab->sample_index);
 	isl_mat_free(tab->basis);
 	free(tab);
 }
@@ -235,6 +236,10 @@ struct isl_tab *isl_tab_dup(struct isl_tab *tab)
 		dup->samples = isl_mat_dup(tab->samples);
 		if (!dup->samples)
 			goto error;
+		dup->sample_index = isl_alloc_array(tab->mat->ctx, int,
+							tab->samples->n_row);
+		if (!dup->sample_index)
+			goto error;
 		dup->n_sample = tab->n_sample;
 		dup->n_outside = tab->n_outside;
 	}
@@ -485,6 +490,7 @@ struct isl_tab *isl_tab_product(struct isl_tab *tab1, struct isl_tab *tab2)
 		prod->row_var[pos] = t;
 	}
 	prod->samples = NULL;
+	prod->sample_index = NULL;
 	prod->n_row = tab1->n_row + tab2->n_row;
 	prod->n_con = tab1->n_con + tab2->n_con;
 	prod->n_eq = 0;
@@ -801,6 +807,9 @@ struct isl_tab *isl_tab_init_samples(struct isl_tab *tab)
 	tab->samples = isl_mat_alloc(tab->mat->ctx, 1, 1 + tab->n_var);
 	if (!tab->samples)
 		goto error;
+	tab->sample_index = isl_alloc_array(tab->mat->ctx, int, 1);
+	if (!tab->sample_index)
+		goto error;
 	return tab;
 error:
 	isl_tab_free(tab);
@@ -813,6 +822,14 @@ struct isl_tab *isl_tab_add_sample(struct isl_tab *tab,
 	if (!tab || !sample)
 		goto error;
 
+	if (tab->n_sample + 1 > tab->samples->n_row) {
+		int *t = isl_realloc_array(tab->mat->ctx,
+			    tab->sample_index, int, tab->n_sample + 1);
+		if (!t)
+			goto error;
+		tab->sample_index = t;
+	}
+
 	tab->samples = isl_mat_extend(tab->samples,
 				tab->n_sample + 1, tab->samples->n_col);
 	if (!tab->samples)
@@ -820,6 +837,7 @@ struct isl_tab *isl_tab_add_sample(struct isl_tab *tab,
 
 	isl_seq_cpy(tab->samples->row[tab->n_sample], sample->el, sample->size);
 	isl_vec_free(sample);
+	tab->sample_index[tab->n_sample] = tab->n_sample;
 	tab->n_sample++;
 
 	return tab;
@@ -831,14 +849,32 @@ error:
 
 struct isl_tab *isl_tab_drop_sample(struct isl_tab *tab, int s)
 {
-	if (s != tab->n_outside)
+	if (s != tab->n_outside) {
+		int t = tab->sample_index[tab->n_outside];
+		tab->sample_index[tab->n_outside] = tab->sample_index[s];
+		tab->sample_index[s] = t;
 		isl_mat_swap_rows(tab->samples, tab->n_outside, s);
+	}
 	tab->n_outside++;
 	isl_tab_push(tab, isl_tab_undo_drop_sample);
 
 	return tab;
 }
 
+/* Record the current number of samples so that we can remove newer
+ * samples during a rollback.
+ */
+void isl_tab_save_samples(struct isl_tab *tab)
+{
+	union isl_tab_undo_val u;
+
+	if (!tab)
+		return;
+
+	u.n = tab->n_sample;
+	push_union(tab, isl_tab_undo_saved_samples, u);
+}
+
 /* Mark row with index "row" as being redundant.
  * If we may need to undo the operation or if the row represents
  * a variable of the original problem, the row is kept,
@@ -2524,6 +2560,28 @@ error:
 	return -1;
 }
 
+/* Remove all samples with index n or greater, i.e., those samples
+ * that were added since we saved this number of samples in
+ * isl_tab_save_samples.
+ */
+static int drop_samples_since(struct isl_tab *tab, int n)
+{
+	int i;
+
+	for (i = tab->n_sample - 1; i >= 0 && tab->n_sample > n; --i) {
+		if (tab->sample_index[i] < n)
+			continue;
+
+		if (i != tab->n_sample - 1) {
+			int t = tab->sample_index[tab->n_sample-1];
+			tab->sample_index[tab->n_sample-1] = tab->sample_index[i];
+			tab->sample_index[i] = t;
+			isl_mat_swap_rows(tab->samples, tab->n_sample-1, i);
+		}
+		tab->n_sample--;
+	}
+}
+
 static int perform_undo(struct isl_tab *tab, struct isl_tab_undo *undo)
 {
 	switch (undo->type) {
@@ -2555,6 +2613,9 @@ static int perform_undo(struct isl_tab *tab, struct isl_tab_undo *undo)
 	case isl_tab_undo_drop_sample:
 		tab->n_outside--;
 		break;
+	case isl_tab_undo_saved_samples:
+		drop_samples_since(tab, undo->u.n);
+		break;
 	default:
 		isl_assert(tab->mat->ctx, 0, return -1);
 	}
diff --git a/isl_tab.h b/isl_tab.h
index 584c535..34535d3 100644
--- a/isl_tab.h
+++ b/isl_tab.h
@@ -30,11 +30,13 @@ enum isl_tab_undo_type {
 	isl_tab_undo_bset_div,
 	isl_tab_undo_saved_basis,
 	isl_tab_undo_drop_sample,
+	isl_tab_undo_saved_samples,
 };
 
 union isl_tab_undo_val {
 	int		var_index;
 	int		*col_var;
+	int		n;
 };
 
 struct isl_tab_undo {
@@ -136,6 +138,7 @@ struct isl_tab {
 
 	unsigned n_sample;
 	unsigned n_outside;
+	int *sample_index;
 	struct isl_mat *samples;
 
 	int n_zero;
@@ -228,5 +231,6 @@ struct isl_tab *isl_tab_init_samples(struct isl_tab *tab);
 struct isl_tab *isl_tab_add_sample(struct isl_tab *tab,
 	__isl_take isl_vec *sample);
 struct isl_tab *isl_tab_drop_sample(struct isl_tab *tab, int s);
+void isl_tab_save_samples(struct isl_tab *tab);
 
 #endif
diff --git a/isl_tab_pip.c b/isl_tab_pip.c
index e88985d..5886fd7 100644
--- a/isl_tab_pip.c
+++ b/isl_tab_pip.c
@@ -1973,6 +1973,7 @@ static struct isl_sol *find_in_pos(struct isl_sol *sol,
 
 	snap = isl_tab_snap(sol->context_tab);
 	isl_tab_push_basis(sol->context_tab);
+	isl_tab_save_samples(sol->context_tab);
 	if (isl_tab_extend_cons(sol->context_tab, 1) < 0)
 		goto error;
 
@@ -2004,6 +2005,7 @@ static struct isl_sol *no_sol_in_strict(struct isl_sol *sol,
 	struct isl_tab_undo *snap;
 	snap = isl_tab_snap(sol->context_tab);
 	isl_tab_push_basis(sol->context_tab);
+	isl_tab_save_samples(sol->context_tab);
 	if (isl_tab_extend_cons(sol->context_tab, 1) < 0)
 		goto error;