vote_atomic_bb.cuh 5.51 KB

# include <iostream>
# include <cuda.h>
#include <stim/cuda/cudatools.h>
#include <stim/cuda/sharedmem.cuh>
#include <stim/visualization/aabb2.h>
#include <stim/visualization/colormap.h>
#include <math.h>

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* gpuGrad, T* gpuTable, T phi, int rmax, size_t x, size_t y, bool gradmag = true){

			extern __shared__ T S[];
			T* shared_atan = S;
			size_t n_table = (rmax * 2 + 1) * (rmax * 2 + 1);
			stim::cuda::threadedMemcpy((char*)shared_atan, (char*)gpuTable, sizeof(T) * n_table, threadIdx.x, blockDim.x);
			// calculate the 2D coordinates for this current thread.
			size_t xi = blockIdx.x * blockDim.x + threadIdx.x;
			size_t yi = blockIdx.y * blockDim.y + threadIdx.y;
			if(xi >= x || yi >= y) return;			
			// convert 2D coordinates to 1D
			size_t i = yi * x + xi;

			// calculate the voting direction based on the grtadient direction
			float theta = gpuGrad[2*i];
			//calculate the amount of vote for the voter
			float mag = gpuGrad[2*i + 1];

			stim::aabb2<int> bb(xi, yi);								//initialize a bounding box at the current point
			bb.insert(xi + ceil(rmax * cos(theta)),       ceil(yi + rmax * sin(theta)));
			bb.insert(xi + ceil(rmax * cos(theta - phi)), yi + ceil(rmax * sin(theta - phi)));		//insert one corner of the triangle into the bounding box
			bb.insert(xi + ceil(rmax * cos(theta + phi)), yi + ceil(rmax * sin(theta + phi)));		//insert the final corner into the bounding box
			// 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;
			int lut_i;
			T dx_sq, dy_sq;

			bb.trim_low(0, 0);															//make sure the bounding box doesn't go outside the image
			bb.trim_high(x-1, y-1);

			size_t by, bx;
			int dx, dy;					
			unsigned int ind_g;											//initialize the maximum vote value to zero
			T alpha;
			for(by = bb.low[1]; by <= bb.high[1]; by++){					//for each element in the bounding box
				dy = by - yi;											//calculate the y coordinate of the current point relative to yi
				dy_sq = dy * dy;
				for(bx = bb.low[0]; bx <= bb.high[0]; bx++){
					dx = bx - xi;
					dx_sq = dx * dx;
					lut_i = (rmax - dy) * x_table + rmax - dx;
					alpha = shared_atan[lut_i];
					if(dx_sq + dy_sq < rmax_sq && abs(alpha - theta) < phi){
						ind_g = (by)*x + (bx);
						if(gradmag) atomicAdd(&gpuVote[ind_g], mag);			//add the gradient magnitude (if the gradmag flag is enabled)
						else		atomicAdd(&gpuVote[ind_g], 1.0f);			//otherwise just add 1

		/// Iterative voting for an image
		/// @param gpuVote is the resulting vote image
		/// @param gpuGrad is the gradient of the input image
		/// @param gpuTable is the pre-computed atan2() table
		/// @param phi is the angle of the vote region
		/// @param rmax is the estimated radius of the blob (defines the "width" of the vote region)
		/// @param x and y are the spatial dimensions of the gradient image
		/// @param gradmag defines whether or not the gradient magnitude is taken into account during the vote
		template<typename T>
		void gpu_vote(T* gpuVote, T* gpuGrad, T* gpuTable, T phi, unsigned int rmax, size_t x, size_t y, bool gradmag = true){
			unsigned int max_threads = stim::maxThreadsPerBlock();
			dim3 threads( (unsigned int)sqrt(max_threads), (unsigned int)sqrt(max_threads) );
			dim3 blocks((unsigned int)x/threads.x + 1, (unsigned int)y/threads.y + 1);
			size_t table_bytes = sizeof(T) * (rmax * 2 + 1) * (rmax * 2 + 1);
			size_t shared_mem_req = table_bytes;// + template_bytes;
			if (DEBUG) std::cout<<"Shared Memory required: "<<shared_mem_req<<std::endl;
			size_t shared_mem = stim::sharedMemPerBlock();
			if(shared_mem_req > shared_mem){
				std::cout<<"Error: insufficient shared memory for this implementation of cuda_update_dir()."<<std::endl;

			//call the kernel to do the voting
			cuda_vote <<< blocks, threads, shared_mem_req>>>(gpuVote, gpuGrad, gpuTable, phi, rmax, x , y, gradmag);


		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