Question

I am continuously getting an Access Violation Error with a all my kernels which I am trying to build. Other kernels which I take from books seem to work fine.

https://github.com/ssarangi/VideoCL – This is where the code is.

Something seems to be missing in this. Could someone help me with this.

Thanks so much.

[James] – Thanks for the suggestion and you are right. I am doing it on Win 7 with a AMD Redwood card. I have the Catalyst 11.7 drivers with AMD APP SDK 2.5. I am posting the code below.

#include <iostream>
#include "bmpfuncs.h"

#include "CLManager.h"

void main()
{
    float theta = 3.14159f/6.0f;
    int W ;
    int H ;

    const char* inputFile = "input.bmp";
    const char* outputFile = "output.bmp";

    float* ip = readImage(inputFile, &W, &H);
    float *op = new float[W*H];

    //We assume that the input image is the array “ip”
    //and the angle of rotation is theta
    float cos_theta = cos(theta);
    float sin_theta = sin(theta);

    try
    {
        CLManager* clMgr = new CLManager();

        // Build the Source
        unsigned int pgmID = clMgr->buildSource("rotation.cl");

        // Create the kernel
        cl::Kernel* kernel = clMgr->makeKernel(pgmID, "img_rotate");

        // Create the memory Buffers
        cl::Buffer* clIp = clMgr->createBuffer(CL_MEM_READ_ONLY, W*H*sizeof(float));
        cl::Buffer* clOp = clMgr->createBuffer(CL_MEM_READ_WRITE, W*H*sizeof(float));

        // Get the command Queue
        cl::CommandQueue* queue = clMgr->getCmdQueue();
        queue->enqueueWriteBuffer(*clIp, CL_TRUE, 0, W*H*sizeof(float), ip);

        // Set the arguments to the kernel
        kernel->setArg(0, clOp);
        kernel->setArg(1, clIp);
        kernel->setArg(2, W);
        kernel->setArg(3, H);
        kernel->setArg(4, sin_theta);
        kernel->setArg(5, cos_theta);

        // Run the kernel on specific NDRange
        cl::NDRange globalws(W, H);


        queue->enqueueNDRangeKernel(*kernel, cl::NullRange, globalws, cl::NullRange);

        queue->enqueueReadBuffer(*clOp, CL_TRUE, 0, W*H*sizeof(float), op);

        storeImage(op, outputFile, H, W, inputFile);
    }
    catch(cl::Error error)
    {
        std::cout << error.what() << "(" << error.err() << ")" << std::endl;
    }
}

I am getting the error at the queue->enqueueNDRangeKernel line.
I have the queue and the kernel stored in a class.

CLManager::CLManager()
    : m_programIDs(-1)
{
    // Initialize the Platform
    cl::Platform::get(&m_platforms);

    // Create a Context
    cl_context_properties cps[3] = {
        CL_CONTEXT_PLATFORM,
        (cl_context_properties)(m_platforms[0])(),
        0
    };

    m_context = cl::Context(CL_DEVICE_TYPE_GPU, cps);

    // Get a list of devices on this platform
    m_devices = m_context.getInfo<CL_CONTEXT_DEVICES>();

    cl_int err;

    m_queue = new cl::CommandQueue(m_context, m_devices[0], 0, &err);
}


cl::Kernel* CLManager::makeKernel(unsigned int programID, std::string kernelName)
{
    cl::CommandQueue queue = cl::CommandQueue(m_context, m_devices[0]);

    cl::Kernel* kernel = new cl::Kernel(*(m_programs[programID]), kernelName.c_str());

    m_kernels.push_back(kernel);

    return kernel;
}

Answer 1

I checked your code. I’m on Linux though. At runtime I’m getting Error -38, which means CL_INVALID_MEM_OBJECT. So I went and checked your buffers.

cl::Buffer* clIp = clMgr->createBuffer(CL_MEM_READ_ONLY, W*H*sizeof(float));
cl::Buffer* clOp = clMgr->createBuffer(CL_MEM_READ_WRITE, W*H*sizeof(float));

Then you pass the buffers as a Pointer:

kernel->setArg(0, clOp);
kernel->setArg(1, clIp);

But setArg is expecting a value, so the buffer pointers should be dereferenced:

kernel->setArg(0, *clOp);
kernel->setArg(1, *clIp);

After those changes the cat rotates 😉