update_dir_global.cuh
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#ifndef STIM_CUDA_UPDATE_DIR_GLOBALD_H
#define STIM_CUDA_UPDATE_DIR_GLOBAL_H
# include <iostream>
# include <cuda.h>
#include <stim/cuda/cudatools.h>
#include <stim/cuda/sharedmem.cuh>
#include "cpyToshare.cuh"
#define RMAX_TEST 8
namespace stim{
namespace cuda{
// this kernel calculates the voting direction for the next iteration based on the angle between the location of this voter and the maximum vote value in its voting area.
template<typename T>
__global__ void cuda_update_dir(T* gpuDir, T* gpuVote, T* gpuGrad, T* gpuTable, T phi, int rmax, int x, int y){
//calculate the start point for this block
int bxi = blockIdx.x * blockDim.x;
// calculate the 2D coordinates for this current thread.
int xi = bxi + threadIdx.x;
if(xi >= x) return; //if the index is outside of the image, terminate the kernel
int yi = blockIdx.y * blockDim.y + threadIdx.y;
int i = yi * x + xi; // convert 2D coordinates to 1D
float theta = gpuGrad[2*i]; // calculate the voting direction based on the grtadient direction - global memory fetch
gpuDir[i] = 0; //initialize the vote direction to zero
float max = 0; // define a local variable to maximum value of the vote image in the voting area for this voter
int id_x = 0; // define two local variables for the x and y position of the maximum
int id_y = 0;
int x_table = 2*rmax +1; // compute the size of window which will be checked for finding the voting area for this voter
int rmax_sq = rmax * rmax;
int tx_rmax = threadIdx.x + rmax;
float atan_angle;
float vote_c;
for(int yr = -RMAX_TEST; yr <= RMAX_TEST; yr++){
if (yi+yr >= 0 && yi + yr < y){
for(int xr = -RMAX_TEST; xr <= RMAX_TEST; xr++){
unsigned int ind_t = (RMAX_TEST - yr) * x_table + RMAX_TEST - xr;
// calculate the angle between the voter and the current pixel in x and y directions
atan_angle = gpuTable[ind_t];
// find the vote value for the current counter
vote_c = gpuVote[(yi+yr)*x + (xi+xr)];
// 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)){
// compare the vote value of this pixel with the max value to find the maxima and its index.
if (vote_c>max) {
max = vote_c;
id_x = xr;
id_y = yr;
}
}
}
}
}
unsigned int ind_m = (rmax - id_y) * x_table + (rmax - id_x);
float new_angle = gpuTable[ind_m];
if(xi < x && yi < y)
gpuDir[i] = new_angle;
} //end kernel
// this kernel updates the gradient direction by the calculated voting direction.
template<typename T>
__global__ void cuda_update_grad(T* gpuGrad, T* gpuDir, int x, int y){
// calculate the 2D coordinates for this current thread.
int xi = blockIdx.x * blockDim.x + threadIdx.x;
int yi = blockIdx.y * blockDim.y + threadIdx.y;
// convert 2D coordinates to 1D
int i = yi * x + xi;
//update the gradient image with the vote direction
gpuGrad[2*i] = gpuDir[i];
}
template<typename T>
void gpu_update_dir(T* gpuVote, T* gpuGrad, T* gpuTable, 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);
unsigned int max_threads = stim::maxThreadsPerBlock();
dim3 threads(max_threads, 1);
dim3 blocks(x/threads.x + (x %threads.x == 0 ? 0:1) , y);
// allocate space on the GPU for the updated vote direction
T* gpuDir;
cudaMalloc(&gpuDir, bytes);
//call the kernel to calculate the new voting direction
cuda_update_dir <<< blocks, threads>>>(gpuDir, gpuVote, gpuGrad, gpuTable, phi, rmax, x , y);
//call the kernel to update the gradient direction
cuda_update_grad <<< blocks, threads >>>(gpuGrad, gpuDir, x , y);
//free allocated memory
cudaFree(gpuDir);
}
template<typename T>
void cpu_update_dir(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);
//copy the input vote image to the GPU
HANDLE_ERROR(cudaMemcpy(gpuVote, cpuVote, bytes, cudaMemcpyHostToDevice));
//allocate space on the GPU for the input Gradient image
T* gpuGrad;
HANDLE_ERROR(cudaMalloc(&gpuGrad, bytes*2));
//copy the Gradient 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 update direction function
gpu_update_dir<T>(gpuVote, gpuGrad, gpuTable, phi, rmax, x , y);
//copy the new gradient image back to the CPU
cudaMemcpy(cpuGrad, gpuGrad, bytes*2, cudaMemcpyDeviceToHost) ;
//free allocated memory
cudaFree(gpuTable);
cudaFree(gpuVote);
cudaFree(gpuGrad);
}
}
}
#endif