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#if !defined CUDA_DISABLER

#include <thrust/device_ptr.h>
#include <thrust/sort.h>

#include "opencv2/core/cuda/common.hpp"
#include "opencv2/core/cuda/utility.hpp"
#include <thrust/execution_policy.h>
namespace cv { namespace cuda { namespace device
{
    namespace gfft
    {
        template <class Mask> __global__ void findCorners(float threshold, const Mask mask, float2* corners, int max_count, int rows, int cols, cudaTextureObject_t eigTex, int *g_counter)
        {
            const int j = blockIdx.x * blockDim.x + threadIdx.x;
            const int i = blockIdx.y * blockDim.y + threadIdx.y;

            if (i > 0 && i < rows - 1 && j > 0 && j < cols - 1 && mask(i, j))
            {
                float val = tex2D<float>(eigTex, j, i);

                if (val > threshold)
                {
                    float maxVal = val;

                    maxVal = ::fmax(tex2D<float>(eigTex, j - 1, i - 1), maxVal);
                    maxVal = ::fmax(tex2D<float>(eigTex, j    , i - 1), maxVal);
                    maxVal = ::fmax(tex2D<float>(eigTex, j + 1, i - 1), maxVal);

                    maxVal = ::fmax(tex2D<float>(eigTex, j - 1, i), maxVal);
                    maxVal = ::fmax(tex2D<float>(eigTex, j + 1, i), maxVal);

                    maxVal = ::fmax(tex2D<float>(eigTex, j - 1, i + 1), maxVal);
                    maxVal = ::fmax(tex2D<float>(eigTex, j    , i + 1), maxVal);
                    maxVal = ::fmax(tex2D<float>(eigTex, j + 1, i + 1), maxVal);

                    if (val == maxVal)
                    {
                        const int ind = ::atomicAdd(g_counter, 1);

                        if (ind < max_count)
                            corners[ind] = make_float2(j, i);
                    }
                }
            }
        }

        int findCorners_gpu(const cudaTextureObject_t &eigTex, const int &rows, const int &cols, float threshold, PtrStepSzb mask, float2* corners, int max_count, cudaStream_t stream)
        {
            int* counter_ptr;
            cudaSafeCall( cudaMalloc(&counter_ptr, sizeof(int)) );

            cudaSafeCall( cudaMemsetAsync(counter_ptr, 0, sizeof(int), stream) );

            dim3 block(16, 16);
            dim3 grid(divUp(cols, block.x), divUp(rows, block.y));

            if (mask.data)
                findCorners<<<grid, block, 0, stream>>>(threshold, SingleMask(mask), corners, max_count, rows, cols, eigTex, counter_ptr);
            else
                findCorners<<<grid, block, 0, stream>>>(threshold, WithOutMask(), corners, max_count, rows, cols, eigTex, counter_ptr);

            cudaSafeCall( cudaGetLastError() );

            int count;
            cudaSafeCall( cudaMemcpyAsync(&count, counter_ptr, sizeof(int), cudaMemcpyDeviceToHost, stream) );
            if (stream)
                cudaSafeCall(cudaStreamSynchronize(stream));
            else
                cudaSafeCall( cudaDeviceSynchronize() );
            return std::min(count, max_count);
        }

        class EigGreater
        {
        public:
            EigGreater(const cudaTextureObject_t &eigTex_) : eigTex(eigTex_)
            {
            }
            __device__ __forceinline__ bool operator()(float2 a, float2 b) const
            {
                return tex2D<float>(eigTex, a.x, a.y) > tex2D<float>(eigTex, b.x, b.y);
            }

            cudaTextureObject_t eigTex;
        };

        void sortCorners_gpu(const cudaTextureObject_t &eigTex, float2* corners, int count, cudaStream_t stream)
        {
            thrust::device_ptr<float2> ptr(corners);
#if THRUST_VERSION >= 100802
            if (stream)
                thrust::sort(thrust::cuda::par(ThrustAllocator::getAllocator()).on(stream), ptr, ptr + count, EigGreater(eigTex));
            else
                thrust::sort(thrust::cuda::par(ThrustAllocator::getAllocator()), ptr, ptr + count, EigGreater(eigTex));
#else
            thrust::sort(ptr, ptr + count, EigGreater(eigTex));
#endif
        }
    } // namespace optical_flow
}}}


#endif /* CUDA_DISABLER */
