local_max.cuh
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#ifndef STIM_CUDA_LOCAL_MAX_H
#define STIM_CUDA_LOCAL_MAX_H
# include <iostream>
# include <cuda.h>
#include <stim/cuda/cudatools.h>
namespace stim{
namespace cuda{
// this kernel calculates the local maximum for finding the cell centers
template<typename T>
__global__ void cuda_local_max(T* gpuCenters, T* gpuVote, T final_t, int conn, int x, int y){
// calculate the 2D coordinates for this current thread.
int xi = blockIdx.x * blockDim.x + threadIdx.x;
int yi = blockIdx.y;
if(xi >= x || yi >= y)
return;
// convert 2D coordinates to 1D
int i = yi * x + xi;
gpuCenters[i] = 0; //initialize the value at this location to zero
T val = gpuVote[i];
//compare to the threshold
if(val < final_t) return;
//define an array to store indices with same vote value
/*int * IdxEq;
IdxEq = new int [2*conn];
int n = 0;*/
for(int xl = xi - conn; xl < xi + conn; xl++){
for(int yl = yi - conn; yl < yi + conn; yl++){
if(xl >= 0 && xl < x && yl >= 0 && yl < y){
int il = yl * x + xl;
if(gpuVote[il] > val){
return;
}
if (gpuVote[il] == val){
/*IdxEq[n] = il;
n = n+1;*/
if( il > i){
return;
}
}
}
}
}
/*if (n!=0){
if(IdxEq[n/2] !=i){
return;
}
} */
gpuCenters[i] = 1;
}
template<typename T>
void gpu_local_max(T* gpuCenters, T* gpuVote, T final_t, unsigned int conn, unsigned int x, unsigned int y){
unsigned int max_threads = stim::maxThreadsPerBlock();
dim3 threads(max_threads, 1);
dim3 blocks(x/threads.x + (x %threads.x == 0 ? 0:1) , y);
//call the kernel to find the local maximum.
cuda_local_max <<< blocks, threads >>>(gpuCenters, gpuVote, final_t, conn, x, y);
}
template<typename T>
void cpu_local_max(T* cpuCenters, T* cpuVote, T final_t, unsigned int conn, unsigned int x, unsigned int y){
//calculate the number of bytes in the array
unsigned int bytes = x * y * sizeof(T);
// allocate space on the GPU for the detected cell centes
T* gpuCenters;
cudaMalloc(&gpuCenters, bytes);
//allocate space on the GPU for the input Vote Image
T* gpuVote;
cudaMalloc(&gpuVote, bytes);
//copy the Vote image data to the GPU
HANDLE_ERROR(cudaMemcpy(gpuVote, cpuVote, bytes, cudaMemcpyHostToDevice));
//call the GPU version of the local max function
gpu_local_max<T>(gpuCenters, gpuVote, final_t, conn, x, y);
//copy the cell centers data to the CPU
cudaMemcpy(cpuCenters, gpuCenters, bytes, cudaMemcpyDeviceToHost) ;
//free allocated memory
cudaFree(gpuCenters);
cudaFree(gpuVote);
}
}
}
#endif