From 472662f668c28fad3af7aea6de22422d0d987376 Mon Sep 17 00:00:00 2001
From: "Kurt A. O'Hearn" <ohearnku@msu.edu>
Date: Fri, 23 Dec 2016 08:40:14 -0800
Subject: [PATCH] sPuReMD: add thread parallelism to conflict detection in
graph coloring.
---
sPuReMD/src/lin_alg.c | 99 ++++++++++++++++++++++++++++++++-----------
1 file changed, 74 insertions(+), 25 deletions(-)
diff --git a/sPuReMD/src/lin_alg.c b/sPuReMD/src/lin_alg.c
index 1759b41c..4ef1ce22 100644
--- a/sPuReMD/src/lin_alg.c
+++ b/sPuReMD/src/lin_alg.c
@@ -52,6 +52,7 @@ unsigned int *top = NULL;
unsigned int *color = NULL;
unsigned int *to_color = NULL;
unsigned int *conflict = NULL;
+unsigned int *conflict_cnt = NULL;
unsigned int *temp_ptr;
unsigned int *recolor = NULL;
unsigned int recolor_cnt;
@@ -534,8 +535,16 @@ void graph_coloring( const sparse_matrix * const A, const TRIANGULARITY tri )
{
#define MAX_COLOR (500)
int i, pj, v;
- unsigned int temp;
- int *fb_color;
+ unsigned int temp, recolor_cnt_local, *conflict_local;
+ int tid, num_thread, *fb_color;
+
+#ifdef _OPENMP
+ tid = omp_get_thread_num();
+ num_thread = omp_get_num_threads();
+#else
+ tid = 0;
+ num_thread = 1;
+#endif
#pragma omp master
{
@@ -562,7 +571,8 @@ void graph_coloring( const sparse_matrix * const A, const TRIANGULARITY tri )
}
}
- if ( (fb_color = (int*) malloc(sizeof(int) * MAX_COLOR)) == NULL )
+ if ( (fb_color = (int*) malloc(sizeof(int) * MAX_COLOR)) == NULL ||
+ (conflict_local = (unsigned int*) malloc(sizeof(unsigned int) * A->n)) == NULL )
{
fprintf( stderr, "not enough memory for graph coloring. terminating.\n" );
exit( INSUFFICIENT_MEMORY );
@@ -598,29 +608,63 @@ void graph_coloring( const sparse_matrix * const A, const TRIANGULARITY tri )
}
/* determine if recoloring required */
- //TODO: switch to reduction on recolor_cnt (+) via parallel scan through recolor
+ temp = recolor_cnt;
+ recolor_cnt_local = 0;
+
+ #pragma omp barrier
+
#pragma omp master
{
- temp = recolor_cnt;
recolor_cnt = 0;
+ }
+
+ #pragma omp barrier
- for ( i = 0; i < temp; ++i )
- {
- v = to_color[i];
+ #pragma omp for schedule(static)
+ for ( i = 0; i < temp; ++i )
+ {
+ v = to_color[i];
- /* search for color conflicts with adjacent vertices */
- for ( pj = A->start[v]; pj < A->start[v + 1]; ++pj )
+ /* search for color conflicts with adjacent vertices */
+ for ( pj = A->start[v]; pj < A->start[v + 1]; ++pj )
+ {
+ if ( color[v] == color[A->j[pj]] && v > A->j[pj] )
{
- if ( color[v] == color[A->j[pj]] && v > A->j[pj] )
- {
- conflict[recolor_cnt] = v;
- color[v] = 0;
- ++recolor_cnt;
- break;
- }
+ conflict_local[recolor_cnt_local] = v;
+ ++recolor_cnt_local;
+ break;
}
}
+ }
+
+ /* count thread-local conflicts and compute offsets for copying into shared buffer */
+ conflict_cnt[tid + 1] = recolor_cnt_local;
+
+ #pragma omp barrier
+
+ #pragma omp master
+ {
+ conflict_cnt[0] = 0;
+ for ( i = 1; i < num_thread + 1; ++i )
+ {
+ conflict_cnt[i] += conflict_cnt[i - 1];
+ }
+ recolor_cnt = conflict_cnt[num_thread];
+ }
+
+ #pragma omp barrier
+ /* copy thread-local conflicts into shared buffer */
+ for ( i = 0; i < recolor_cnt_local; ++i )
+ {
+ conflict[conflict_cnt[tid] + i] = conflict_local[i];
+ color[conflict_local[i]] = 0;
+ }
+
+ #pragma omp barrier
+
+ #pragma omp master
+ {
temp_ptr = to_color;
to_color = conflict;
conflict = temp_ptr;
@@ -629,16 +673,9 @@ void graph_coloring( const sparse_matrix * const A, const TRIANGULARITY tri )
#pragma omp barrier
}
+ free( conflict_local );
free( fb_color );
-//#if defined(DEBUG)
-// #pragma omp master
-// {
-// for ( i = 0; i < A->n; ++i )
-// printf("Vertex: %5d, Color: %5d\n", i, color[i] );
-// }
-//#endif
-
#pragma omp barrier
}
}
@@ -877,12 +914,24 @@ void permute_matrix( sparse_matrix * const LU, const TRIANGULARITY tri )
*/
sparse_matrix * setup_graph_coloring( sparse_matrix * const H )
{
+ int num_thread;
+
if ( color == NULL )
{
+#ifdef _OPENMP
+ #pragma omp parallel
+ {
+ num_thread = omp_get_num_threads();
+ }
+#else
+ num_thread = 1;
+#endif
+
/* internal storage for graph coloring (global to facilitate simultaneous access to OpenMP threads) */
if ( (color = (unsigned int*) malloc(sizeof(unsigned int) * H->n)) == NULL ||
(to_color =(unsigned int*) malloc(sizeof(unsigned int) * H->n)) == NULL ||
(conflict = (unsigned int*) malloc(sizeof(unsigned int) * H->n)) == NULL ||
+ (conflict_cnt = (unsigned int*) malloc(sizeof(unsigned int) * (num_thread + 1))) == NULL ||
(recolor = (unsigned int*) malloc(sizeof(unsigned int) * H->n)) == NULL ||
(color_top = (unsigned int*) malloc(sizeof(unsigned int) * (H->n + 1))) == NULL ||
(permuted_row_col = (unsigned int*) malloc(sizeof(unsigned int) * H->n)) == NULL ||
--
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