opencv/modules/gpu/src/cuda/hough.cu

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#include <thrust/sort.h>
#include "opencv2/gpu/device/common.hpp"
#include "opencv2/gpu/device/emulation.hpp"

namespace cv { namespace gpu { namespace device
{
    namespace hough
    {
        __device__ int g_counter;

        ////////////////////////////////////////////////////////////////////////
        // buildPointList

        const int PIXELS_PER_THREAD = 16;

        __global__ void buildPointList(const DevMem2Db src, unsigned int* list)
        {
            __shared__ int s_queues[4][32 * PIXELS_PER_THREAD];
            __shared__ int s_qsize[4];
            __shared__ int s_globStart[4];

            const int x = blockIdx.x * blockDim.x * PIXELS_PER_THREAD + threadIdx.x;
            const int y = blockIdx.y * blockDim.y + threadIdx.y;

            if (y >= src.rows)
                return;

            if (threadIdx.x == 0)
                s_qsize[threadIdx.y] = 0;

            __syncthreads();

            // fill the queue
            const uchar* srcRow = src.ptr(y);
            for (int i = 0, xx = x; i < PIXELS_PER_THREAD && xx < src.cols; ++i, xx += blockDim.x)
            {
                if (srcRow[xx])
                {
                    const unsigned int val = (y << 16) | xx;
                    const int qidx = Emulation::smem::atomicAdd(&s_qsize[threadIdx.y], 1);
                    s_queues[threadIdx.y][qidx] = val;
                }
            }

            __syncthreads();

            // let one thread reserve the space required in the global list
            if (threadIdx.x == 0 && threadIdx.y == 0)
            {
                // find how many items are stored in each list
                int totalSize = 0;
                for (int i = 0; i < blockDim.y; ++i)
                {
                    s_globStart[i] = totalSize;
                    totalSize += s_qsize[i];
                }

                // calculate the offset in the global list
                const int globalOffset = atomicAdd(&g_counter, totalSize);
                for (int i = 0; i < blockDim.y; ++i)
                    s_globStart[i] += globalOffset;
            }

            __syncthreads();

            // copy local queues to global queue
            const int qsize = s_qsize[threadIdx.y];
            int gidx = s_globStart[threadIdx.y] + threadIdx.x;
            for(int i = threadIdx.x; i < qsize; i += blockDim.x, gidx += blockDim.x)
                list[gidx] = s_queues[threadIdx.y][i];
        }

        int buildPointList_gpu(DevMem2Db src, unsigned int* list)
        {
            void* counterPtr;
            cudaSafeCall( cudaGetSymbolAddress(&counterPtr, g_counter) );

            cudaSafeCall( cudaMemset(counterPtr, 0, sizeof(int)) );

            const dim3 block(32, 4);
            const dim3 grid(divUp(src.cols, block.x * PIXELS_PER_THREAD), divUp(src.rows, block.y));

            cudaSafeCall( cudaFuncSetCacheConfig(buildPointList, cudaFuncCachePreferShared) );

            buildPointList<<<grid, block>>>(src, list);
            cudaSafeCall( cudaGetLastError() );

            cudaSafeCall( cudaDeviceSynchronize() );

            int totalCount;
            cudaSafeCall( cudaMemcpy(&totalCount, counterPtr, sizeof(int), cudaMemcpyDeviceToHost) );

            return totalCount;
        }

        ////////////////////////////////////////////////////////////////////////
        // linesAccum

        __global__ void linesAccumGlobal(const unsigned int* list, const int count, PtrStepi accum, const float irho, const float theta, const int numrho)
        {
            const int n = blockIdx.x;
            const float ang = n * theta;

            float sinVal;
            float cosVal;
            sincosf(ang, &sinVal, &cosVal);
            sinVal *= irho;
            cosVal *= irho;

            const int shift = (numrho - 1) / 2;

            int* accumRow = accum.ptr(n + 1);
            for (int i = threadIdx.x; i < count; i += blockDim.x)
            {
                const unsigned int val = list[i];

                const int x = (val & 0xFFFF);
                const int y = (val >> 16) & 0xFFFF;

                int r = __float2int_rn(x * cosVal + y * sinVal);
                r += shift;

                ::atomicAdd(accumRow + r + 1, 1);
            }
        }

        __global__ void linesAccumShared(const unsigned int* list, const int count, PtrStepi accum, const float irho, const float theta, const int numrho)
        {
            extern __shared__ int smem[];

            for (int i = threadIdx.x; i < numrho + 1; i += blockDim.x)
                smem[i] = 0;

            __syncthreads();

            const int n = blockIdx.x;
            const float ang = n * theta;

            float sinVal;
            float cosVal;
            sincosf(ang, &sinVal, &cosVal);
            sinVal *= irho;
            cosVal *= irho;

            const int shift = (numrho - 1) / 2;

            for (int i = threadIdx.x; i < count; i += blockDim.x)
            {
                const unsigned int val = list[i];

                const int x = (val & 0xFFFF);
                const int y = (val >> 16) & 0xFFFF;

                int r = __float2int_rn(x * cosVal + y * sinVal);
                r += shift;

                Emulation::smem::atomicAdd(&smem[r + 1], 1);
            }

            __syncthreads();

            int* accumRow = accum.ptr(n + 1);
            for (int i = threadIdx.x; i < numrho + 1; i += blockDim.x)
                accumRow[i] = smem[i];
        }

        void linesAccum_gpu(const unsigned int* list, int count, DevMem2Di accum, float rho, float theta, size_t sharedMemPerBlock, bool has20)
        {
            const dim3 block(has20 ? 1024 : 512);
            const dim3 grid(accum.rows - 2);

            cudaSafeCall( cudaFuncSetCacheConfig(linesAccumShared, cudaFuncCachePreferShared) );

            size_t smemSize = (accum.cols - 1) * sizeof(int);

            if (smemSize < sharedMemPerBlock - 1000)
                linesAccumShared<<<grid, block, smemSize>>>(list, count, accum, 1.0f / rho, theta, accum.cols - 2);
            else
                linesAccumGlobal<<<grid, block>>>(list, count, accum, 1.0f / rho, theta, accum.cols - 2);

            cudaSafeCall( cudaGetLastError() );

            cudaSafeCall( cudaDeviceSynchronize() );
        }

        ////////////////////////////////////////////////////////////////////////
        // linesGetResult

        __global__ void linesGetResult(const DevMem2Di accum, float2* out, int* votes, const int maxSize, const float rho, const float theta, const float threshold, const int numrho)
        {
            __shared__ int smem[8][32];

            const int x = blockIdx.x * (blockDim.x - 2) + threadIdx.x;
            const int y = blockIdx.y * (blockDim.y - 2) + threadIdx.y;

            if (x >= accum.cols || y >= accum.rows)
                return;

            smem[threadIdx.y][threadIdx.x] = accum(y, x);
            __syncthreads();

            const int r = x - 1;
            const int n = y - 1;

            if (threadIdx.x == 0 || threadIdx.x == blockDim.x - 1 || threadIdx.y == 0 || threadIdx.y == blockDim.y - 1 || r >= accum.cols - 2 || n >= accum.rows - 2)
                return;

            if (smem[threadIdx.y][threadIdx.x] > threshold &&
                smem[threadIdx.y][threadIdx.x] >  smem[threadIdx.y - 1][threadIdx.x] &&
                smem[threadIdx.y][threadIdx.x] >= smem[threadIdx.y + 1][threadIdx.x] &&
                smem[threadIdx.y][threadIdx.x] >  smem[threadIdx.y][threadIdx.x - 1] &&
                smem[threadIdx.y][threadIdx.x] >= smem[threadIdx.y][threadIdx.x + 1])
            {
                const float radius = (r - (numrho - 1) * 0.5f) * rho;
                const float angle = n * theta;

                const int ind = ::atomicAdd(&g_counter, 1);
                if (ind < maxSize)
                {
                    out[ind] = make_float2(radius, angle);
                    votes[ind] = smem[threadIdx.y][threadIdx.x];
                }
            }
        }

        int linesGetResult_gpu(DevMem2Di accum, float2* out, int* votes, int maxSize, float rho, float theta, float threshold, bool doSort)
        {
            void* counterPtr;
            cudaSafeCall( cudaGetSymbolAddress(&counterPtr, g_counter) );

            cudaSafeCall( cudaMemset(counterPtr, 0, sizeof(int)) );

            const dim3 block(32, 8);
            const dim3 grid(divUp(accum.cols, block.x - 2), divUp(accum.rows, block.y - 2));

            linesGetResult<<<grid, block>>>(accum, out, votes, maxSize, rho, theta, threshold, accum.cols - 2);
            cudaSafeCall( cudaGetLastError() );

            cudaSafeCall( cudaDeviceSynchronize() );

            int totalCount;
            cudaSafeCall( cudaMemcpy(&totalCount, counterPtr, sizeof(int), cudaMemcpyDeviceToHost) );

            totalCount = ::min(totalCount, maxSize);

            if (doSort && totalCount > 0)
            {
                thrust::device_ptr<float2> outPtr(out);
                thrust::device_ptr<int> votesPtr(votes);
                thrust::sort_by_key(votesPtr, votesPtr + totalCount, outPtr, thrust::greater<int>());
            }

            return totalCount;
        }
    }
}}}