shmem_barrier_all

Purpose

Registers the arrival of a processing element (PE) at a barrier and suspends PE execution until all other PEs arrive at the barrier.

C syntax

#include <shmem.h>
 
void shmem_barrier_all(void);
 

Parameters

Description

Barriers are a fast way to synchronize all PEs

shmem_barrier_all function registers the arrival of the calling PE at a barrier. It also causes the PE to suspend execution until all PEs have arrived shmem_barrier_all.

Before returning from shmem_barrier_all, all previously issued local memory stores and remote memory updates issued via IBM openshmem calls such as shmem_put, are ensured finished.

IBM NOTES

Please refer to Atomicity and Coherency section for atomicity and coherence model in the OpenSHMEM documentation

C examples

#include <stdlib.h>
#include <stdio.h>

#include <shmem.h>

#define GLOBAL_ARRAY_SIZE     20
#define SOURCE_STRIDE         3
#define TARGET_STRIDE         4
#define NUM_OF_TRANS_ELEM     5

static int gIntArray[GLOBAL_ARRAY_SIZE] = {0};

int main (int argc, char* argv[])
{
    int total_tasks = -1;
    int my_task = -1;

    start_pes(0);

    total_tasks = _num_pes();

    if (total_tasks <= 0) {
        printf("FAILED\n");
        exit(1);
    } else {
        printf("number of pes is %d\n", total_tasks);
    }

    if (total_tasks < 2 || total_tasks % 2) {
        printf("FAILED: The number of pes should be an even number. (at least 2)\n");
        exit(1);
    }

    my_task = _my_pe();

    if (my_task < 0){
        printf("FAILED\n");
        exit(1);
    } else {
        printf("my pe id is %d\n", my_task);
    }

    printf("The address of gIntArray is %p\n", gIntArray);

    // even tasks put value to odd tasks
    if (my_task%2 == 0) {
        int tgt_task = my_task + 1;
   
        printf("The Source Stride is: %d, the following data will be put.\n", SOURCE_STRIDE);

        }
        shmem_int_iput(gIntArray, gIntArray, TARGET_STRIDE, SOURCE_STRIDE, NUM_OF_TRANS_ELEM, tgt_task);
    }

    shmem_barrier_all();

Related information

Subroutines: shmem_barrier, shmem_init


OpenSHMEM API Index