creating subbuffer in openCL

Question

I'm trying to run my first codes in OpenCL. I have the following code from the "OpenCL in Action" book in order to create subbuffer. The code gives me error failing in subbuffer creation. My computer has an Intel CPU and NVIDIA GPU. However, when I run the code in another computer with AMD CPU and GPU it works fine. Any idea why this code doesn't work on non-AMD platform? Here is the error:

and this is the code:

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>

#ifdef MAC
#include <OpenCL/cl.h>
#else
#include <CL/cl.h>
#endif

/* Find a GPU or CPU associated with the first available platform */
cl_device_id create_device() {

    cl_platform_id platform;
    cl_device_id dev;
    int err;


    /* Identify a platform */
    err = clGetPlatformIDs(1, &platform, NULL);
    if (err < 0) {
        perror("Couldn't identify a platform");
        exit(1);
    }

    /* Access a device */
    err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_GPU, 1, &dev, NULL);
    if (err == CL_DEVICE_NOT_FOUND) {
        err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_CPU, 1, &dev, NULL);
    }
    if (err < 0) {
        perror("Couldn't access any devices");
        exit(1);
    }

    return dev;
}

int main() {

    /* Host/device data structures */
    cl_device_id device;
    cl_context context;
    cl_int err;

    /* Data and buffers */
    float main_data[100] = {};
    cl_mem main_buffer, sub_buffer;
    void *main_buffer_mem = NULL, *sub_buffer_mem = NULL;
    size_t main_buffer_size, sub_buffer_size;
    cl_buffer_region region;

    /* Create device and context */
    device = create_device();
    context = clCreateContext(NULL, 1, &device, NULL, NULL, &err);
    if (err < 0) {
        perror("Couldn't create a context");
        exit(1);
    }

    /* Create a buffer to hold 100 floating-point values */
    main_buffer = clCreateBuffer(context, CL_MEM_READ_ONLY |
        CL_MEM_COPY_HOST_PTR, sizeof(main_data), main_data, &err);
    if (err < 0) {
        perror("Couldn't create a buffer");
        exit(1);
    }

    /* Create a sub-buffer */
    /* Modified on 2/12/2014 to account for unaligned memory error */
    region.origin = 0 * sizeof(float);
    region.size = 20 * sizeof(float);
    sub_buffer = clCreateSubBuffer(main_buffer, CL_MEM_READ_ONLY |
        CL_MEM_COPY_HOST_PTR, CL_BUFFER_CREATE_TYPE_REGION, &region, &err);
    if (err < 0) {
        perror("Couldn't create a sub-buffer.");
        exit(1);
    }

    /* Obtain size information about the buffers */
    clGetMemObjectInfo(main_buffer, CL_MEM_SIZE,
        sizeof(main_buffer_size), &main_buffer_size, NULL);
    clGetMemObjectInfo(sub_buffer, CL_MEM_SIZE,
        sizeof(sub_buffer_size), &sub_buffer_size, NULL);
    printf("Main buffer size: %lu\n", main_buffer_size);
    printf("Sub-buffer size:  %lu\n", sub_buffer_size);

    /* Obtain the host pointers */
    clGetMemObjectInfo(main_buffer, CL_MEM_HOST_PTR, sizeof(main_buffer_mem),
        &main_buffer_mem, NULL);
    clGetMemObjectInfo(sub_buffer, CL_MEM_HOST_PTR, sizeof(sub_buffer_mem),
        &sub_buffer_mem, NULL);
    printf("Main buffer memory address: %p\n", main_buffer_mem);
    printf("Sub-buffer memory address:  %p\n", sub_buffer_mem);

    /* Print the address of the main data */
    printf("Main array address: %p\n", main_data);

    /* Deallocate resources */
    clReleaseMemObject(main_buffer);
    clReleaseMemObject(sub_buffer);
    clReleaseContext(context);

    return 0;
}

simpel01 simpel01 · Accepted Answer · 2015-11-23T07:19:57

Since you already allocated the memory for the buffer when main_buffer was created, you don't need to do that again when getting a sub-buffer. You should use only CL_MEM_READ_ONLY as cl_mem_flags:

sub_buffer = clCreateSubBuffer(main_buffer, CL_MEM_READ_ONLY,
                               CL_BUFFER_CREATE_TYPE_REGION, &region, &err);

creating subbuffer in openCL

1 Answers