shmem_int_g

Purpose

Transfers one data item from a remote Processing Element (PE).

C syntax

#include <shmem.h>
 
int shmem_int_g(int *addr, int pe);
 

Parameters

INPUT
addr
The remotely accessible data object which will receive the data on the remote PE.
pe
Processing element number of the remote PE.

Description

This routine provides a very low latency remote read write capability for single elements of most basic types

The function shmem_int_g() transfers an integer data item from a remote PE.

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 10
#define INT_INIT_VALUE 1234
//can not use #define
const float FLOAT_INIT_VALUE = 1234.123456;

static float gFloatElement = 0;
static float gFloatArray[GLOBAL_ARRAY_SIZE] = {0};

static int gIntElement = 0;
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 gIntElement is %p\n", &gIntElement);
    printf("The address of gIntArray is %p\n", gIntArray);
    printf("The address of gFloatElement is %p\n", &gFloatElement);
    printf("The address of gFloatArray is %p\n", gFloatArray);

    if (my_task%2 == 0) {
        //for int
        gIntElement = INT_INIT_VALUE;
        for (int i=0; i<GLOBAL_ARRAY_SIZE; i++) {
            gIntArray[i] = INT_INIT_VALUE;
        }
        //for float
        gFloatElement = FLOAT_INIT_VALUE;
        for (int i=0; i<GLOBAL_ARRAY_SIZE; i++) {
            gFloatArray[i] = FLOAT_INIT_VALUE;
        }
    }

    shmem_barrier_all();

    if (my_task%2 == 1) {
        int src_task = my_task - 1;
        //for int
        int element = shmem_int_g(&gIntElement, src_task);
        if (element != INT_INIT_VALUE) {
            printf("FAILED: element should be %d instead of %d\n", INT_INIT_VALUE, element);
            exit(1);
        }

        shmem_int_get(gIntArray, gIntArray, GLOBAL_ARRAY_SIZE, src_task);
        for (int i=0; i<GLOBAL_ARRAY_SIZE; i++) {
            if (gIntArray[i] != INT_INIT_VALUE) {
                printf("FAILED, array[%d] should be %d instead of %d\n", i, INT_INIT_VALUE, gIntArray[i]);
            }
        }
        //for float
        float fElement = shmem_float_g(&gFloatElement, src_task);
        if (fElement != FLOAT_INIT_VALUE) {
            printf("FAILED: element should be %f instead of %f\n", FLOAT_INIT_VALUE, fElement);
            exit(1);
        }

        shmem_float_get(gFloatArray, gFloatArray, GLOBAL_ARRAY_SIZE, src_task);
        for (int i=0; i<GLOBAL_ARRAY_SIZE; i++) {
            if (gFloatArray[i] != FLOAT_INIT_VALUE) {
                printf("FAILED, array[%d] should be %f instead of %f\n", i, FLOAT_INIT_VALUE, gFloatArray[i]);
            }
        }
    }

    shmem_barrier_all();

    printf("PASSED\n");
    return 0;
}

Related information

Subroutines: shmem_get, shmem_iget


OpenSHMEM API Index