local_max3.cuh
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#ifndef STIM_CUDA_LOCAL_MAX3_H
#define STIM_CUDA_LOCAL_MAX3_H
#include <iostream>
#include <cuda.h>
#include <stim/cuda/cudatools.h>
template<typename T>
__global__ void cuda_local_max3(T* gpu_center, T* gpu_vote, int conn_x, int conn_y, int conn_z, int x, int y, int z){
//calculate x,y,z coordinates for this thread
int xi = blockIdx.x * blockDim.x + threadIdx.x;
//find the grid size along y
int grid_y = y / blockDim.y;
int blockidx_y = blockIdx.y % grid_y;
int yi = blockidx_y * blockDim.y + threadIdx.y;
int zi = blockIdx.y / grid_y;
int i = zi * x * y + yi * x + xi;
if (xi>=x || yi>=y || zi>=z) return;
//initilize the center value for this pixel to zero
gpu_center[i] = 0;
//initialize the max value to the vote value for this pixle.
T lv_i = gpu_vote[i];
for (int xl = xi - conn_x; xl <= xi + conn_x; xl++){
for (int yl = yi - conn_y; yl <= yi + conn_y; yl++){
for (int zl = zi - conn_z ; zl <= zi + conn_z; zl++){
if (xl>=0 && yl>=0 && zl>=0 && xl<x && yl<y && zl<z){
int i_l = zl * x * y + yl * x + xl;
if (gpu_vote[i_l] > lv_i) return;
if (gpu_vote[i_l] == lv_i){
if( i_l > i){
return;
}
}
}
}
}
}
gpu_center[i] = lv_i;
}
template<typename T>
void gpu_local_max3(T* gpu_output, T* gpu_vote, T t, unsigned int conn[], unsigned int x, unsigned int y, unsigned int z){
//find the max number of threads per block.
unsigned int max_threads = stim::maxThreadsPerBlock();
dim3 threads(sqrt (max_threads),sqrt (max_threads));
dim3 blocks(x / threads.x + 1, (y / threads.y + 1) * z);
//call the kernel to find the local max
cuda_local_max3<T><<<blocks, threads>>>(gpu_output, gpu_vote, conn[0], conn[1], conn[2], x, y, z);
}
template<typename T>
void cpu_local_max3(T* cpu_output, T* cpu_vote, T t, unsigned int conn[], unsigned int x, unsigned int y, unsigned int z){
//calculate the number of bytes in the data set.
unsigned int bytes = x * y * z * sizeof(T);
//allocate space on the gpu for the vote data and the output.
T* gpu_vote;
cudaMalloc(&gpu_vote, bytes);
T* gpu_output;
cudaMalloc(&gpu_output, bytes);
//copy the vote data to the gpu.
cudaMemcpy(gpu_vote, cpu_vote, bytes, cudaMemcpyHostToDevice);
//call the gpu version of local max function.
gpu_local_max3<T>(gpu_output, gpu_vote, t, conn, x ,y, z);
//copy the detected result to the cpu.
cudaMemcpy(cpu_output, gpu_output, bytes, cudaMemcpyDeviceToHost);
cudaFree(gpu_vote);
cudaFree(gpu_output);
}
#endif