[SOLVED] Problems additionVector with OpenCL

I want to learn OpenCL so i read a tutorial with a simple vector addition https://www.eriksmistad.no/getting-started-with-opencl-and-gpu-computing/ Im working with ubuntu

Distributor ID: Ubuntu
Description:    Ubuntu 22.04.1 LTS
Release:    22.04
Codename:   jammy

And i have a RTX 3080Ti known by my computer

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 525.85.05    Driver Version: 525.85.05    CUDA Version: 12.0     |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|===============================+======================+======================|
|   0  NVIDIA GeForce ...  Off  | 00000000:02:00.0  On |                  N/A |
|  0%   54C    P8    38W / 350W |    634MiB / 12288MiB |      2%      Default |
|                               |                      |                  N/A |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|=============================================================================|
|    0   N/A  N/A      1766      G   /usr/lib/xorg/Xorg                312MiB |
|    0   N/A  N/A      2087      G   /usr/bin/gnome-shell              105MiB |
|    0   N/A  N/A      3343      G   ...5/usr/lib/firefox/firefox      183MiB |
+-----------------------------------------------------------------------------+

give by an nvidia-smi

I installed OpenCL with apt-get install opencl-headers and cuda for OpenCL drivers.

Here is the code :

#include <stdio.h>
#include <stdlib.h>
 
#ifdef __APPLE__
#include <OpenCL/opencl.h>
#else
#include <CL/cl.h>
#endif
 
#define MAX_SOURCE_SIZE (0x100000)
 
int main(void) {
    // Create the two input vectors
    int i;
    const int LIST_SIZE = 10;
    int *A = (int*)malloc(sizeof(int)*LIST_SIZE);
    int *B = (int*)malloc(sizeof(int)*LIST_SIZE);
    for(i = 0; i < LIST_SIZE; i++) {
        A[i] = i;
        B[i] = i;
    }
 
    // Load the kernel source code into the array source_str
    FILE *fp;
    char *source_str;
    size_t source_size;
    char str_buffer[1024];
 
    fp = fopen("vector_add_kernel.cl", "r");
    if (!fp) {
        fprintf(stderr, "Failed to load kernel.\n");
        exit(1);
    }
    source_str = (char*)malloc(MAX_SOURCE_SIZE);
    source_size = fread( source_str, 1, MAX_SOURCE_SIZE, fp);
    fclose( fp );
 
    // Get platform and device information
    cl_platform_id platform_id = NULL;
    cl_device_id device_id = NULL;   
    cl_uint ret_num_devices;
    cl_uint ret_num_platforms;
    cl_int ret = clGetPlatformIDs(1, &platform_id, &ret_num_platforms);
    ret = clGetDeviceIDs( platform_id, CL_DEVICE_TYPE_GPU, 1, 
            &device_id, &ret_num_devices);


    // Create an OpenCL context
    cl_context context = clCreateContext( NULL, 1, &device_id, NULL, NULL, &ret);
 
    // Create a command queue
    cl_command_queue command_queue = clCreateCommandQueue(context, device_id, 0, &ret);
 
    // Create memory buffers on the device for each vector 
    cl_mem a_mem_obj = clCreateBuffer(context, CL_MEM_READ_ONLY, 
            LIST_SIZE * sizeof(int), NULL, &ret);
    cl_mem b_mem_obj = clCreateBuffer(context, CL_MEM_READ_ONLY,
            LIST_SIZE * sizeof(int), NULL, &ret);
    cl_mem c_mem_obj = clCreateBuffer(context, CL_MEM_WRITE_ONLY, 
            LIST_SIZE * sizeof(int), NULL, &ret);
 
    // Copy the lists A and B to their respective memory buffers
    ret = clEnqueueWriteBuffer(command_queue, a_mem_obj, CL_TRUE, 0,
            LIST_SIZE * sizeof(int), A, 0, NULL, NULL);
    ret = clEnqueueWriteBuffer(command_queue, b_mem_obj, CL_TRUE, 0, 
            LIST_SIZE * sizeof(int), B, 0, NULL, NULL);
 
    // Create a program from the kernel source
    cl_program program = clCreateProgramWithSource(context, 1, 
            (const char **)&source_str, (const size_t *)&source_size, &ret);
 
    // Build the program
    ret = clBuildProgram(program, 1, &device_id, NULL, NULL, NULL);
 
    // Create the OpenCL kernel
    cl_kernel kernel = clCreateKernel(program, "vector_add", &ret);
 
    // Set the arguments of the kernel
    ret = clSetKernelArg(kernel, 0, sizeof(cl_mem), (void *)&a_mem_obj);
    ret = clSetKernelArg(kernel, 1, sizeof(cl_mem), (void *)&b_mem_obj);
    ret = clSetKernelArg(kernel, 2, sizeof(cl_mem), (void *)&c_mem_obj);
 
    // Execute the OpenCL kernel on the list
    size_t global_item_size = LIST_SIZE; // Process the entire lists
    size_t local_item_size = 64; // Divide work items into groups of 64
    ret = clEnqueueNDRangeKernel(command_queue, kernel, 1, NULL, 
            &global_item_size, &local_item_size, 0, NULL, NULL);
 
    // Read the memory buffer C on the device to the local variable C
    int *C = (int*)malloc(sizeof(int)*LIST_SIZE);
    ret = clEnqueueReadBuffer(command_queue, c_mem_obj, CL_TRUE, 0, 
            LIST_SIZE * sizeof(int), C, 0, NULL, NULL);
 
    // Display the result to the screen
    for(i = 0; i < LIST_SIZE; i++)
        printf("%d + %d = %d\n", A[i], B[i], C[i]);
 
    // Clean up
    ret = clFlush(command_queue);
    ret = clFinish(command_queue);
    ret = clReleaseKernel(kernel);
    ret = clReleaseProgram(program);
    ret = clReleaseMemObject(a_mem_obj);
    ret = clReleaseMemObject(b_mem_obj);
    ret = clReleaseMemObject(c_mem_obj);
    ret = clReleaseCommandQueue(command_queue);
    ret = clReleaseContext(context);
    free(A);
    free(B);
    free(C);
    return 0;
}

And the code of the kernel :

__kernel void vector_add(__global const int *A, __global const int *B, __global int *C) {
 
    // Get the index of the current element to be processed
    int i = get_global_id(0);
    
    // Do the operation
    C[i] = A[i] + B[i];
}

I compile with : gcc main.c -o vectorAddition -l OpenCL

And the execution of vectorAddition give me this :

platform name : NVIDIA CUDA
platform vendor : NVIDIA Corporation
Device name : NVIDIA Corporation
0 + 0 = 0
1 + 1 = 0
2 + 2 = 0
3 + 3 = 0
4 + 4 = 0
5 + 5 = 0
6 + 6 = 0
7 + 7 = 0
8 + 8 = 0
9 + 9 = 0

Thanks

I already read a post which is pretty the same than mine : https://stackoverflow.com/questions/54606449/opencl-vector-addition-program But i think my clCreateBuffer are good

I put these lines in my code to be sure my gpu is know :

    //Get the name of the platform and device
    ret = clGetPlatformInfo(0, CL_PLATFORM_NAME, sizeof(str_buffer), &str_buffer, NULL);
    printf("platform name : %s\n",str_buffer);
    ret = clGetPlatformInfo(0, CL_PLATFORM_VENDOR, sizeof(str_buffer), &str_buffer, NULL);
    printf("platform vendor : %s\n",str_buffer);
    ret = clGetDeviceInfo(0, CL_DEVICE_NAME, sizeof(str_buffer), &str_buffer, NULL);
    printf("Device name : %s\n",str_buffer);