vote_threshold_global.cuh
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#ifndef STIM_CUDA_VOTE_THRESHOLD_GLOBAL_H
#define STIM_CUDA_VOTE_THRESHOLD_GLOBAL_H
# include <iostream>
# include <cuda.h>
#include <stim/cuda/cudatools.h>
#include <stim/cuda/sharedmem.cuh>
#include "cpyToshare.cuh"
namespace stim{
namespace cuda{
// this kernel calculates the vote value by adding up the gradient magnitudes of every voter that this pixel is located in their voting area
template<typename T>
__global__ void cuda_vote(T* gpuVote, T* gpuTh, T* gpuTable, T phi, int rmax, int th_size, int x, int y){
// calculate the x coordinate for this current thread.
int xi = blockIdx.x * blockDim.x + threadIdx.x;
// calculate the voting direction based on the grtadient direction
float theta = gpuTh[3*xi];
//find the gradient magnitude for the current voter
float mag = gpuTh[3*xi + 1];
//calculate the position and x, y coordinations of this voter in the original image
unsigned int i_v = gpuTh[3*xi+2];
unsigned int y_v = i_v/x;
unsigned int x_v = i_v - (y_v*x);
// compute the size of window which will be checked for finding the proper voters for this pixel
int x_table = 2*rmax +1;
int rmax_sq = rmax * rmax;
if(xi < th_size){
for(int yr = -rmax; yr <= rmax; yr++){
for(int xr = -rmax; xr <= rmax; xr++){
if ((y_v+yr)>=0 && (y_v+yr)<y && (x_v+xr)>=0 && (x_v+xr)<x){
//find the location of the current pixel in the atan2 table
unsigned int ind_t = (rmax - yr) * x_table + rmax - xr;
// calculate the angle between the voter and the current pixel in x and y directions
float atan_angle = gpuTable[ind_t];
// check if the current pixel is located in the voting area of this voter.
if (((xr * xr + yr *yr)< rmax_sq) && (abs(atan_angle - theta) <phi)){
// calculate the 1D index for the current pixel in global memory
unsigned int ind_g = (y_v+yr)*x + (x_v+xr);
atomicAdd(&gpuVote[ind_g], mag);
}
}
}
}
}
}
template<typename T>
void gpu_vote(T* gpuVote, T* gpuTh, T* gpuTable, T phi, unsigned int rmax, unsigned int th_size, unsigned int x, unsigned int y){
unsigned int max_threads = stim::maxThreadsPerBlock();
dim3 threads(max_threads);
dim3 blocks(th_size/threads.x + 1);
//call the kernel to do the voting
cuda_vote <<< blocks, threads>>>(gpuVote, gpuTh, gpuTable, phi, rmax, th_size, x , y);
}
template<typename T>
void cpu_vote(T* cpuVote, T* cpuGrad,T* cpuTable, T phi, unsigned int rmax, unsigned int x, unsigned int y){
//calculate the number of bytes in the array
unsigned int bytes = x * y * sizeof(T);
//calculate the number of bytes in the atan2 table
unsigned int bytes_table = (2*rmax+1) * (2*rmax+1) * sizeof(T);
//allocate space on the GPU for the Vote Image
T* gpuVote;
cudaMalloc(&gpuVote, bytes);
//allocate space on the GPU for the input Gradient image
T* gpuGrad;
HANDLE_ERROR(cudaMalloc(&gpuGrad, bytes*2));
//copy the Gradient Magnitude data to the GPU
HANDLE_ERROR(cudaMemcpy(gpuGrad, cpuGrad, bytes*2, cudaMemcpyHostToDevice));
//allocate space on the GPU for the atan2 table
T* gpuTable;
HANDLE_ERROR(cudaMalloc(&gpuTable, bytes_table));
//copy the atan2 values to the GPU
HANDLE_ERROR(cudaMemcpy(gpuTable, cpuTable, bytes_table, cudaMemcpyHostToDevice));
//call the GPU version of the vote calculation function
gpu_vote<T>(gpuVote, gpuGrad, gpuTable, phi, rmax, x , y);
//copy the Vote Data back to the CPU
cudaMemcpy(cpuVote, gpuVote, bytes, cudaMemcpyDeviceToHost) ;
//free allocated memory
cudaFree(gpuTable);
cudaFree(gpuVote);
cudaFree(gpuGrad);
}
}
}
#endif