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//------------------------------------------------------------------------------
// GraphBLAS/Demo/Program/reduce_demo: reduce a matrix to a scalar
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
#include "GraphBLAS.h"
#if defined ( _OPENMP )
#include <omp.h>
#endif
// #define N 65536
#define N 16384
int main (void)
{
#if defined ( _OPENMP )
double t0 = omp_get_wtime ( ) ;
#endif
// start GraphBLAS
GrB_init (GrB_NONBLOCKING) ;
int nthreads ;
GxB_Global_Option_get (GxB_GLOBAL_NTHREADS, &nthreads) ;
printf ("demo: reduce a matrix to a scalar, nthreads: %d\n", nthreads) ;
int nthreads_max ;
GxB_Global_Option_get (GxB_GLOBAL_NTHREADS, &nthreads_max) ;
printf ("# of threads: %d\n", nthreads_max) ;
#if defined ( _OPENMP )
t0 = omp_get_wtime ( ) - t0 ;
printf ("GPU warmup time: %g\n", t0) ;
t0 = omp_get_wtime ( ) ;
#endif
GrB_Index nrows = N ;
GrB_Index ncols = N ;
GrB_Matrix A ;
GrB_Matrix_new (&A, GrB_INT64, nrows, ncols) ;
GrB_Index *I = (GrB_Index *) malloc (nrows * ncols * sizeof (GrB_Index)) ;
GrB_Index *J = (GrB_Index *) malloc (nrows * ncols * sizeof (GrB_Index)) ;
int64_t *X = (int64_t *) malloc (nrows * ncols * sizeof (int64_t)) ;
int64_t k ;
#pragma omp parallel for num_threads(nthreads_max) schedule(static)
for (k = 0 ; k < N*N ; k++)
{
// k = i * N + j ;
int64_t i = k / N ;
int64_t j = k % N ;
// int x = (int) (rand ( ) & 0xFF) ;
int x = (int) (k & 0xFF) ;
I [k] = i ;
J [k] = j ;
X [k] = x ;
}
GrB_Index nvals = N*N ;
GrB_Matrix_build_INT64 (A, I, J, X, nvals, GrB_PLUS_INT64) ;
free (I) ;
free (J) ;
free (X) ;
#if defined ( _OPENMP )
t0 = omp_get_wtime ( ) - t0 ;
printf ("time to create matrix: %g\n", t0) ;
#endif
GrB_Index result ;
double t1 ;
printf ("\nreduce to a scalar:\n") ;
for (int nthreads = 1 ; nthreads <= nthreads_max ; nthreads++)
{
GxB_Global_Option_set (GxB_GLOBAL_NTHREADS, nthreads) ;
#if defined ( _OPENMP )
double t = omp_get_wtime ( ) ;
#endif
GrB_Matrix_reduce_UINT64 (&result, NULL, GrB_PLUS_MONOID_INT64,
A, NULL) ;
#if defined ( _OPENMP )
t = omp_get_wtime ( ) - t ;
if (nthreads == 1) t1 = t ;
printf ("nthreads %3d time: %12.6f speedup %8.2f\n",
nthreads, t, t1/t) ;
#endif
}
printf ("result %" PRId64 "\n", result) ;
// free everyting
GrB_Matrix_free (&A) ;
GrB_finalize ( ) ;
}
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