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Thread: Call OpenCL functions from another file

  1. #1
    Junior Member
    Join Date
    Sep 2012

    Call OpenCL functions from another file

    I have a main C source where there is the main loop for doing iterative computation. Here is this main loop :
    Code :
                 step = step + 1;
                 t    = t + dt;
                 Explicit(source, source_size, x0, x, size_x, size_y, diagx, diagy,
        	                weightx, weighty, &error, k0) ;
                 result = sqrt(error);
               if ((result<epsilon) || (step>maxStep)) break;

    As you can see in this loop, I call `Explicit` function which contains all the required OpenCL functions for computing the next values of x0 at each iteration. Here's a part of this another source :

    Code :
    #include <stdio.h>
    #include <CL/cl.h>
        void Explicit( const char* source, size_t source_size, double** x0, double** x,
        int size_x, int size_y, double diagx, double diagy, double weightx, double
        weighty, double* error, double k0)
        /* local variables */
         int i,j,iter;
         double rk, eps, time, result;
         double* r;
        // Allocate cumulative error array
             r = malloc((size_x+2)*(size_y+2)*sizeof(double));
        // 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_CPU, 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 x0_mem_obj = clCreateBuffer(context, CL_MEM_READ_ONLY,
                    (size_x+2) * (size_y+2) * sizeof(cl_double), NULL, &ret);
            // Execute the OpenCL kernel on the list
            size_t global_item_size[2] = {size_y,size_x}; 
            // Process the entire lists
            ret = clEnqueueNDRangeKernel(command_queue, kernel, 2, NULL, 
                    global_item_size, NULL, 0, NULL, NULL);
             // Read the buffer back to the array
             readBuffer2D(command_queue, x_mem_obj, x, size_x, size_y);
             ret = clEnqueueReadBuffer(command_queue, r_mem_obj, CL_TRUE, 0, 
                    (size_x+2) * (size_y+2) * sizeof(double), r, 0, NULL, NULL);	    

    The problem is that if I put this `Explicit` function in another C source, the code compiles fine but doesn't give good results ( x0 array values all to zero ).

    If I include this function into the main file, i.e into only one source, the code works fine. Is this specific to OpenCL parameters passing ?

    Anyone could help me please.

  2. #2
    Senior Member
    Join Date
    Aug 2011

    Re: Call OpenCL functions from another file

    There's nothing special about the C conventions used in the host code.

    You probably just have a mismatch of the function prototypes, or some logic problem (like returning local variable addresses), but there isn't enough code shown to tell. Try compiling with -Wall to see what's going on.

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