offload/test/offloading/strided_update/strided_update_partial_to.c

// This test checks that #pragma omp target update to(data[0:4:3]) correctly
// updates every third element (stride 3) from the host to the device, partially
// across the array

// RUN: %libomptarget-compile-run-and-check-generic

#include <omp.h>
#include <stdio.h>

int main() {
  int len = 11;
  double data[len];

  // Initialize on host
  for (int i = 0; i < len; i++)
    data[i] = i;

  // Initial values
  printf("original host array values:\n");
  for (int i = 0; i < len; i++)
    printf("%f\n", data[i]);
  printf("\n");

  // CHECK: 0.000000
  // CHECK: 1.000000
  // CHECK: 2.000000
  // CHECK: 3.000000
  // CHECK: 4.000000
  // CHECK: 5.000000
  // CHECK: 6.000000
  // CHECK: 7.000000
  // CHECK: 8.000000
  // CHECK: 9.000000
  // CHECK: 10.000000

#pragma omp target data map(tofrom : data[0 : len])
  {
    // Initialize device array to 20
#pragma omp target
    for (int i = 0; i < len; i++)
      data[i] = 20.0;

    // Modify host data for strided elements
    data[0] = 10.0;
    data[3] = 10.0;
    data[6] = 10.0;
    data[9] = 10.0;

#pragma omp target update to(data[0 : 4 : 3]) // indices 0,3,6,9

    // Verify on device by adding 5
#pragma omp target
    for (int i = 0; i < len; i++)
      data[i] += 5.0;
  }

  printf("device array values after update to:\n");
  for (int i = 0; i < len; i++)
    printf("%f\n", data[i]);
  printf("\n");

  // CHECK: 15.000000
  // CHECK: 25.000000
  // CHECK: 25.000000
  // CHECK: 15.000000
  // CHECK: 25.000000
  // CHECK: 25.000000
  // CHECK: 15.000000
  // CHECK: 25.000000
  // CHECK: 25.000000
  // CHECK: 15.000000
  // CHECK: 25.000000
}