Hello opencl community,

I just started learning opencl. In the last few days, I solved my programing problems by myself. Since yesterday, I have a problem I cannot solve by myself. So, I ask for your help.

After some hello-world tutorial programs I started with little complex tasks. I want to use an implemented opencl kernel to encrypt some short passwords.

My frist question is, whether I have to buffer a single value variable (for expl. a single factor) the same way as arrays/pointers to pass it to the kernel.

I wrote this program:
Code :
#include <fstream>
#include <iostream>
#include <iterator>
#include <CL/cl.hpp>
#include <CL/opencl.h>
using namespace std;
int main () {
    vector<cl::Platform> platforms;
    vector<cl::Device> devices;
    vector<cl::Kernel> kernels;
    try {
        // create platform
        platforms[0].getDevices(CL_DEVICE_TYPE_GPU, &devices);
        // create context
        cl::Context context(devices);
        // create command queue
        cl::CommandQueue queue(context, devices[0]);
        // load opencl source
        ifstream cl_file("pbkdf2_kernel.cl");
        string cl_string(istreambuf_iterator<char>(cl_file), (istreambuf_iterator<char>()));
        cl::Program::Sources source(1, make_pair(cl_string.c_str(), 
            cl_string.length() + 1));
        // create program
        cl::Program program(context, source);
        // compile opencl source
        // load named kernel from opencl source
        cl::Kernel kernel(program, "PBKDF2");
        // create a message to send to kernel ----------------------------------------------------------------
        char* password = "C & OpenCL is cool";
        //unsigned int keyBytes = 18; // keyBytes
        cl_int keyBytes = 18; // keyBytes  
        char* passwordSalt = "12345678901234567890123456789012";
        cl_int passwordSaltLen = 32;
        cl_int passwordIterations = 2;
        // ---------------------------------------------------------------------------------------------------
        // allocate device buffer to hold message
        cl::Buffer bufferA(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(char) * keyBytes, password);
        cl::Buffer bufferB(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(char) * passwordSaltLen, passwordSalt);
        cl::Buffer bufferC(context, CL_MEM_WRITE_ONLY, sizeof(char) * keyBytes);
        queue.enqueueWriteBuffer(bufferA, CL_TRUE, 0, keyBytes * sizeof(char), password);
        queue.enqueueWriteBuffer(bufferB, CL_TRUE, 0, passwordSaltLen * sizeof(char), passwordSalt);
//void PBKDF2 ( const __global unsigned int *pass_global,
//              const __global unsigned int *salt, int usrlen, uint num_keys, __global unsigned int *out_global)
        // set message as kernel argument
        kernel.setArg(0, bufferA);
        kernel.setArg(1, bufferB);
        kernel.setArg(2, passwordIterations);
        kernel.setArg(3, keyBytes);
         // execute kernel
        // wait for completion
        // ----------------------
        char* out_global = "                 !";
	queue.enqueueReadBuffer(bufferC, CL_TRUE, 0, keyBytes * sizeof(char), out_global);
        cout << "Output " << out_global << endl;
        // ----------------------
        cout << endl;
    } catch (cl::Error e) {
        cout << endl << e.what() << " : " << e.err() << endl;
    return 0;

Well, the used implementation of pbkdf2-hmac-sha1 can be accessed by the function:
Code :
void PBKDF2 ( const __global unsigned int *pass_global, const __global unsigned int *salt, int usrlen, uint num_keys, __global unsigned int *out_global) {

The used implementation of pbkdf2-hmac-sha1 is written by Sayantan Datta.

I get to following error msg, I cannot handle:
clEnqueueTask : -52
Can someone help, please?

Thank you,