CODEWITHSUNDEEP
ckernelbufferopencl
George W
George W

Reputation: 51

OpenCL buffers and data calculation

If I want to format this code into OpenCL what should I consider when doing so? Like what buffers should I be using? And if I want to know how much data the kernel use doing this, how am I able to calculate it?

int A[100000]
int B[100000]

    for(int i=1; i<100000 -1); i++) {
      B[i] = A[i-1] + A[i+1] - 2*A[i]
    }

All help is appreciated

Upvotes: 1

Views: 155

Answers (1)

lawful_neutral
lawful_neutral

Reputation: 673

You need two buffers for A and B. For example:

cl_int error = CL_SUCCESS;
cl_mem A_buffer = clCreateBuffer(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(int)*100000, A, &error);
cl_mem B_buffer = clCreateBuffer(context, CL_MEM_READ_WRITE | CL_MEM_COPY_HOST_PTR, sizeof(int)*100000, B, &error);

If you want each kernel to work with only one element of B, then your global work size would equal 99999.

Your kernel might look somehow like this (in case one thread works with one value, you might not need such parallelism, it's just an example):

kernel void your_kernel(global int* A, global int* B) {
    int i = get_global_id(0);
    B[i] = A[i-1] + A[i+1] - 2*A[i];
}

Upvotes: 2

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