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Thread: system goes into some indefinite loop - adding two vectors

  1. #1
    Junior Member
    Join Date
    Oct 2009

    system goes into some indefinite loop - adding two vectors

    Hi, i am being able to compile this code but it doesn't give me any output and goes in some indefinite loop (or something else)... i dont understand whats happening. I'm a newbie to OpenCL and this is my first program.. All i'm trying to do is add two vectors. I get no errors during the compilation. If i am not wrong, i should see the 'End' that i've printed after the gpu portion completes right?

    This is the machine detail that i'm running the code on:
    Linux gpu02.cluster 2.6.18-92.1.22.el5 #1 SMP Tue Dec 16 11:57:43 EST 2008 x86_64 x86_64 x86_64 GNU/Linux

    Code :
    #include <stdio.h>
    #include <CL/cl.h>
    #define SIZE 10
    int va[SIZE];
    int vb[SIZE];
    int vc[SIZE];
    char* load_program_source(const char*);
    int Init(){
            int i;
    char* load_program_source(const char *filename)
            int fileSize = 0;
            FILE *pFile = fopen(filename, "r");
            fseek(pFile, 0, SEEK_END);
            fileSize = ftell(pFile);
            char *data = (char*) calloc(sizeof(char), fileSize+1);
            fread(data, 1, fileSize, pFile);
            return data;
    int main(){
                    printf("Unable to initialize data");
                    return 1;
            cl_context GPUContext = clCreateContextFromType(0,CL_DEVICE_TYPE_GPU, NULL, NULL, NULL);
                    printf("Error: Failed to create context");
                    return 1;
            //Get the list of GPU devices associated with this context
            size_t ParmDataBytes;
            clGetContextInfo(GPUContext, CL_CONTEXT_DEVICES, 0, NULL, &ParmDataBytes);
            cl_device_id* GPUDevices = (cl_device_id*)malloc(ParmDataBytes);
            clGetContextInfo(GPUContext, CL_CONTEXT_DEVICES, ParmDataBytes,GPUDevices,NULL);
            //Create a command queue on first gpu device
            cl_command_queue GPUCommandQueue = clCreateCommandQueue(GPUContext, GPUDevices[0],0,NULL);
                    printf("Error: Failed to create a command queue");
                    return 1;
            //Allocate memory
            cl_mem GPUva = clCreateBuffer(GPUContext, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(int)*SIZE, va, NULL);
            cl_mem GPUvb = clCreateBuffer(GPUContext, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(int)*SIZE, vb, NULL);
            cl_mem GPUvc = clCreateBuffer(GPUContext, CL_MEM_WRITE_ONLY, sizeof(int)*SIZE, NULL, NULL);
            //Create OCL program reading the source code from the file
            char * OclSource = load_program_source("");
            cl_program  OpenCLProgram = clCreateProgramWithSource(GPUContext,1,(const char**)&OclSource,NULL,NULL);
            //Build the program
            //obtain the handle for the kernel
            cl_kernel OpenCLVectorAdd = clCreateKernel(OpenCLProgram,"VectorAdd",NULL);
           //associate GPU memory with the kernel
            clSetKernelArg(OpenCLVectorAdd, 0, sizeof(cl_mem), (void*)&GPUvc);
            clSetKernelArg(OpenCLVectorAdd, 1, sizeof(cl_mem), (void*)&GPUvb);
            clSetKernelArg(OpenCLVectorAdd, 2, sizeof(cl_mem), (void*)&GPUva);
            //Launch the kernel in the GPU
            size_t WorkSize[1] = {SIZE};
            clEnqueueNDRangeKernel(GPUCommandQueue, OpenCLVectorAdd,1,NULL,WorkSize,NULL,0,NULL,NULL);
            //copy the result back to the main memory
            clEnqueueReadBuffer(GPUCommandQueue, GPUvc, CL_TRUE,0,sizeof(int) * SIZE, vc, 0, NULL, NULL);
            return 0;

    this is my kernel code:

    Code :
    __kernel void VectorAdd(__global int* vc, __global int* vb, __global int* va){
            int i;

    could anyone please help me with it?

    Thanks a lot

  2. #2

    Re: system goes into some indefinite loop - adding two vectors

    Size in the c code is 10. Loop in the kernel loops 100 times. Result is that you overflow your memory objects.

    With that change, and the addition of a print loop:

    0 + 6 = 6
    5 + 7 = 12
    0 + 2 = 2
    0 + 9 = 9
    9 + 4 = 13
    1 + 0 = 1
    8 + 0 = 8
    3 + 0 = 3
    9 + 0 = 9
    1 + 3 = 4

    Runs fine on CPU and GPU on my MacBook Pro (10.6.2)

  3. #3
    Junior Member
    Join Date
    Oct 2009

    Re: system goes into some indefinite loop - adding two vectors

    well how do you run the code? Its just like running a simple .c code isn't it? or is there something else to do, because it's not changing the output when i change that to 10.
    I compile the code like:
    Code :
    gcc -o vectoradd vectoradd.c -lOpenCL
    vectoradd.c: In function ‘load_program_source’:
    vectoradd.c:30: warning: incompatible implicit declaration of built-in function ‘calloc’
    vectoradd.c: In function ‘main’:
    vectoradd.c:52: warning: incompatible implicit declaration of built-in function ‘malloc’

    and i run the code like:
    Code :
    cl]$ ./vectoradd

    do i need to specify anything else?

  4. #4
    Junior Member
    Join Date
    Oct 2009

    Re: system goes into some indefinite loop - adding two vectors

    and one more thing. I'm connecting to a remote server and working on it using ssh, should that cause any problems in producing the output on the screen?

  5. #5
    Junior Member
    Join Date
    Oct 2009

    Re: system goes into some indefinite loop - adding two vectors

    Sorry for all the trouble folks - it was the stupid PC that causing problems, not the code in itself. Thanks a lot.

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