update_dir3.cuh
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#ifndef STIM_CUDA_UPDATE_DIR3_H
#define STIM_CUDA_UPDATE_DIR3_H
# include <iostream>
# include <cuda.h>
#include <stim/cuda/cudatools.h>
#include <stim/cuda/sharedmem.cuh>
#include <cuda_fp16.h>
// 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 update_dir3(T* gpu_dir, T* gpu_grad, T* gpu_vote, T cos_phi, int rx, int ry, int rz, 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;
//find the gradient values along the x, y ,z axis, and the gradient magnitude for the voter
float g_v_x = gpu_grad[i * 3 + 0];
float g_v_y = gpu_grad[i * 3 + 1];
float g_v_z = gpu_grad[i * 3 + 2];
float mag_v = sqrt( g_v_x * g_v_x + g_v_y * g_v_y + g_v_z * g_v_z);
// define a local variable to maximum value of the vote image in the voting area for this voter
float max = 0;
float l_vote = 0;
// define local variables for the x, y, and z coordinations point to the vote direction
float id_x = g_v_x;
float id_y = g_v_y;
float id_z = g_v_z;
int rx_sq = rx * rx;
int ry_sq = ry * ry;
int rz_sq = rz * rz;
for (int z_p = -rz; z_p<=rz; z_p++){
for(int y_p = -ry; y_p <= ry; y_p++){
for(int x_p = -rx; x_p <= rx; x_p++){
//calculate the x, y ,z indices for the current pixel
int xi_p = (xi + x_p) ;
int yi_p = (yi + y_p) ;
int zi_p = (zi + z_p) ;
if (zi_p >=0 && zi_p < z && yi_p >=0 && yi_p < y && xi_p >=0 && xi_p < x){
//calculate the distance between the pixel and the current voter.
float x_sq = x_p * x_p;
float y_sq = y_p * y_p;
float z_sq = z_p * z_p;
float d_pv = sqrt(x_sq + y_sq + z_sq);
// calculate the angle between the pixel and the current voter.
float cos_diff = (g_v_x * x_p + g_v_y * y_p + g_v_z * z_p)/(d_pv * mag_v);
if ((((x_sq)/rx_sq + (y_sq)/ry_sq + (z_sq)/rz_sq)<= 1) && (cos_diff >= cos_phi)){
//calculate the 1D index for the current pixel
unsigned int id_p = (zi_p) * x * y + (yi_p) * x + (xi_p);
l_vote = gpu_vote[id_p];
// compare the vote value of this pixel with the max value to find the maxima and its index.
if (l_vote>max) {
max = l_vote;
id_x = x_p;
id_y = y_p;
id_z = z_p;
}
}
}
}
}
}
float m_id = sqrt (id_x*id_x + id_y*id_y + id_z*id_z);
gpu_dir[i * 3 + 0] = mag_v * (id_x/m_id);
gpu_dir[i * 3 + 1] = mag_v * (id_y/m_id);
gpu_dir[i * 3 + 2] = mag_v * (id_z/m_id);
}
// this kernel updates the gradient direction by the calculated voting direction.
template<typename T>
__global__ void update_grad3(T* gpu_grad, T* gpu_dir, 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;
//update the gradient image with the new direction direction
gpu_grad[i * 3 + 0] = gpu_dir [i * 3 + 0];
gpu_grad[i * 3 + 1] = gpu_dir [i * 3 + 1];
gpu_grad[i * 3 + 2] = gpu_dir [i * 3 + 2];
}
template<typename T>
void gpu_update_dir3(T* gpu_grad, T* gpu_vote, T cos_phi, unsigned int r[], unsigned int x, unsigned int y, unsigned int z){
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);
// allocate space on the GPU for the updated vote direction
T* gpu_dir;
cudaMalloc(&gpu_dir, x * y * z * sizeof(T) * 3);
//call the kernel to calculate the new voting direction
update_dir3 <<< blocks, threads >>>(gpu_dir, gpu_grad, gpu_vote, cos_phi, r[0], r[1], r[2], x , y, z);
//call the kernel to update the gradient direction
update_grad3 <<< blocks, threads >>>(gpu_grad, gpu_dir, x , y, z);
//free allocated memory
cudaFree(gpu_dir);
}
template<typename T>
void cpu_update_dir3(T* cpu_grad, T* cpu_vote, T cos_phi, unsigned int r[], unsigned int x, unsigned int y, unsigned int z){
//calculate the number of bytes in the array
unsigned int bytes = x * y * z * sizeof(T);
//allocate space on the GPU for the Vote data
T* gpu_vote;
cudaMalloc(&gpu_vote, bytes);
//copy the input vote data to the GPU
cudaMemcpy(gpu_vote, cpu_vote, bytes, cudaMemcpyHostToDevice);
//allocate space on the GPU for the Gradient data
T* gpu_grad;
cudaMalloc(&gpu_grad, bytes*3);
//copy the Gradient data to the GPU
cudaMemcpy(gpu_grad, cpu_grad, bytes*3, cudaMemcpyHostToDevice);
//call the GPU version of the update direction function
gpu_update_dir3<T>(gpu_grad, gpu_vote, cos_phi, r, x , y, z);
//copy the new gradient image back to the CPU
cudaMemcpy(cpu_grad, gpu_grad, bytes*3, cudaMemcpyDeviceToHost) ;
//free allocated memory
cudaFree(gpu_vote);
cudaFree(gpu_grad);
}
#endif