OpenCL

// create a compute context with GPU device context = clCreateContextFromType(CL_DEVICE_TYPE_GPU);  // create a work-queue queue = clCreateWorkQueue(context, NULL, NULL, 0);  // allocate the buffer memory objects memobjs[0] = clCreateBuffer(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(float)*2*num_entries, srcA); memobjs[1] = clCreateBuffer(context, CL_MEM_READ_WRITE, sizeof(float)*2*num_entries, NULL);  // create the compute program program = clCreateProgramFromSource(context, 1, &fft1D_1024_kernel_src, NULL);  // build the compute program executable clBuildProgramExecutable(program, false, NULL, NULL);  // create the compute kernel kernel = clCreateKernel(program, “fft1D_1024”);  // create N-D range object with work-item dimensions global_work_size[0] = n; local_work_size[0] = 64; range = clCreateNDRangeContainer(context, 0, 1, global_work_size, local_work_size);  // set the args values clSetKernelArg(kernel, 0, (void *)&memobjs[0], sizeof(cl_mem), NULL); clSetKernelArg(kernel, 1, (void *)&memobjs[1], sizeof(cl_mem), NULL); clSetKernelArg(kernel, 2, NULL, sizeof(float)*(local_work_size[0]+1)*16, NULL); clSetKernelArg(kernel, 3, NULL, sizeof(float)*(local_work_size[0]+1)*16, NULL);   // execute kernel clExecuteKernel(queue, kernel, NULL, range, NULL, 0, NULL); 

// This kernel computes FFT of length 1024. The 1024 length FFT is decomposed into  // calls to a radix 16 function, another radix 16 function and then a radix 4 function  __kernel void fft1D_1024 (__global float2 *in, __global float2 *out,                            __local float *sMemx, __local float *sMemy) {    int tid = get_local_id(0);    int blockIdx = get_group_id(0) * 1024 + tid;    float2 data[16];    // starting index of data to/from global memory    in = in + blockIdx;  out = out + blockIdx;    globalLoads(data, in, 64); // coalesced global reads    fftRadix16Pass(data);      // in-place radix-16 pass    twiddleFactorMul(data, tid, 1024, 0);    // local shuffle using local memory    localShuffle(data, sMemx, sMemy, tid, (((tid & 15) * 65) + (tid >> 4)));    fftRadix16Pass(data);               // in-place radix-16 pass    twiddleFactorMul(data, tid, 64, 4); // twiddle factor multiplication    localShuffle(data, sMemx, sMemy, tid, (((tid >> 4) * 64) + (tid & 15)));    // four radix-4 function calls    fftRadix4Pass(data); fftRadix4Pass(data + 4);    fftRadix4Pass(data + 8); fftRadix4Pass(data + 12);    // coalesced global writes    globalStores(data, out, 64);  }