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//------------------------------------------------------------------------------
// GraphBLAS/Demo/Program/openmp_demo: example of user multithreading
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2020, All Rights Reserved.
// http://suitesparse.com See GraphBLAS/Doc/License.txt for license.
//------------------------------------------------------------------------------
// This demo uses OpenMP, and should work if GraphBLAS is compiled to
// use either OpenMP or pthreads to synchronize multiple user threadds.
// If OpenMP is not available, this program will work fine without it, in a
// single user thread, regardless of the thread mechanism used by GraphBLAS.
#include "GraphBLAS.h"
#ifdef _OPENMP
#include <omp.h>
#endif
#if defined __INTEL_COMPILER
#pragma warning (disable: 58 167 144 177 181 186 188 589 593 869 981 1418 1419 1572 1599 2259 2282 2557 2547 3280 )
#elif defined __GNUC__
#pragma GCC diagnostic ignored "-Wunknown-pragmas"
#pragma GCC diagnostic ignored "-Wunused-parameter"
#if !defined ( __cplusplus )
#pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
#endif
#endif
#define NTHREADS 8
#define NTRIALS 10
#define N 6
#define OK(method) \
{ \
GrB_Info info = method ; \
if (! (info == GrB_SUCCESS || info == GrB_NO_VALUE)) \
{ \
printf ("Failure (id: %d, info: %d): %s\n", \
id, info, GrB_error ( )) ; \
/* return to caller (do not use inside critical section) */ \
return (0) ; \
} \
}
//------------------------------------------------------------------------------
// worker
//------------------------------------------------------------------------------
int worker (GrB_Matrix *Ahandle, int id)
{
printf ("\n================= worker %d starts:\n", id) ;
fprintf (stderr, "worker %d\n", id) ;
OK (GrB_Matrix_new (Ahandle, GrB_FP64, N, N)) ;
GrB_Matrix A = *Ahandle ;
// worker generates an intentional error message
GrB_Matrix_setElement_INT32 (A, 42, 1000+id, 1000+id) ;
// print the intentional error generated when the worker started
#pragma omp critical
{
// critical section
printf ("\n----------------- worker %d intentional error:\n", id) ;
printf ("%s\n", GrB_error ( )) ;
}
for (int hammer_hard = 0 ; hammer_hard < NTRIALS ; hammer_hard++)
{
for (int i = 0 ; i < N ; i++)
{
for (int j = 0 ; j < N ; j++)
{
double x = (i+1)*100000 + (j+1)*1000 + id ;
OK (GrB_Matrix_setElement_FP64 (A, x, i, j)) ;
}
}
// force completion
GrB_Index nvals ;
OK (GrB_Matrix_nvals (&nvals, A)) ;
}
// Printing is done in a critical section, just so it is not overly
// jumbled. Each matrix and error will print in a single body of text,
// but the order of the matrices and errors printed will be out of order
// because the critical section does not enforce the order that the
// threads enter.
GrB_Info info2 ;
#pragma omp critical
{
// critical section
printf ("\n----------------- worker %d is done:\n", id) ;
info2 = GxB_Matrix_fprint (A, "A", GxB_SHORT, stdout) ;
}
OK (info2) ;
// worker generates an intentional error message
GrB_Matrix_setElement_INT32 (A, 42, 1000+id, 1000+id) ;
// print the intentional error generated when the worker started
// It should be unchanged.
#pragma omp critical
{
// critical section
printf ("\n----------------- worker %d error should be same:\n", id) ;
printf ("%s\n", GrB_error ( )) ;
}
return (0) ;
}
//------------------------------------------------------------------------------
// openmp_demo main program
//------------------------------------------------------------------------------
int main (int argc, char **argv)
{
fprintf (stderr, "Demo: %s:\n", argv [0]) ;
printf ("Demo: %s:\n", argv [0]) ;
// initialize the mutex
int id = -1 ;
// start GraphBLAS
OK (GrB_init (GrB_NONBLOCKING)) ;
int nthreads ;
OK (GxB_Global_Option_get (GxB_GLOBAL_NTHREADS, &nthreads)) ;
fprintf (stderr, "openmp demo, nthreads %d\n", nthreads) ;
// Determine which user-threading model is being used.
GxB_Thread_Model thread_safety ;
GxB_Global_Option_get (GxB_THREAD_SAFETY, &thread_safety) ;
printf ("GraphBLAS is using ") ;
switch (thread_safety)
{
case GxB_THREAD_POSIX :
printf ("a POSIX pthread mutex\n") ;
break ;
case GxB_THREAD_WINDOWS :
printf ("a Windows CriticalSection\n") ;
break ;
case GxB_THREAD_ANSI :
printf ("an ANSI C11 mtx_lock\n") ;
break ;
case GxB_THREAD_OPENMP :
printf ("an OpenMP critical section\n") ;
break ;
default : // GxB_THREAD_NONE
#ifdef _OPENMP
printf ("(nothing! This will fail!)\n") ;
#else
printf ("nothing (OK since user program is single-threaded)\n") ;
#endif
break ;
}
printf ("to synchronize user threads.\n") ;
#ifdef _OPENMP
printf ("User threads in this program are OpenMP threads.\n") ;
#else
printf ("This user program is single threaded.\n") ;
#endif
GrB_Matrix Aarray [NTHREADS] ;
// create the threads
#pragma omp parallel for num_threads(NTHREADS)
for (id = 0 ; id < NTHREADS ; id++)
{
worker (&Aarray [id], id) ;
}
// the master thread prints them again, and frees them
for (int id = 0 ; id < NTHREADS ; id++)
{
GrB_Matrix A = Aarray [id] ;
printf ("\n---- Master prints matrix %d\n", id) ;
OK (GxB_Matrix_fprint (A, "A", GxB_SHORT, stdout)) ;
GrB_Matrix_free (&A) ;
}
// print an error message
printf ("\n\n---- Master thread prints an error message:\n") ;
GrB_Matrix_new (NULL, GrB_FP64, 1, 1) ;
printf ("Error: %s\n", GrB_error ( )) ;
// finish GraphBLAS
GrB_finalize ( ) ;
// finish OpenMP
exit (0) ;
}
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