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//
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//  copy or use the software.
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//
//                           License Agreement
//                For Open Source Computer Vision Library
//
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// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
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#include "precomp.hpp"

#if !defined(HAVE_CUDA)

namespace cv { namespace gpu {

class MultiGpuManager::Impl {};
MultiGpuManager::MultiGpuManager() { throw_nogpu(); }
MultiGpuManager::~MultiGpuManager() {}
void MultiGpuManager::init() { throw_nogpu(); }
void MultiGpuManager::gpuOn(int) { throw_nogpu(); }
void MultiGpuManager::gpuOff() { throw_nogpu(); }

}}

#else

#include <vector>
#include <cuda.h>

#define cuSafeCall(expr) safeCall(expr, #expr, __FILE__, __LINE__)

using namespace std;

namespace cv { namespace gpu {


class MultiGpuManager::Impl
{
public:
    Impl();

    ~Impl()
    {
        for (int i = 0; i < num_devices_; ++i)
            cuSafeCall(cuCtxDestroy(contexts_[i]));
    }

    void gpuOn(int gpu_id)
    {
        if (gpu_id < 0 || gpu_id >= num_devices_)
            CV_Error(CV_StsBadArg, "MultiGpuManager::gpuOn: GPU ID is out of range");
        cuSafeCall(cuCtxPushCurrent(contexts_[gpu_id]));
    }

    void gpuOff()
    {
        CUcontext prev_context;
        cuSafeCall(cuCtxPopCurrent(&prev_context));
    }

private:
    void safeCall(CUresult code, const char* expr, const char* file, int line)
    {
        if (code != CUDA_SUCCESS)
            error(expr, file, line, "");
    }

    int num_devices_;
    vector<CUcontext> contexts_;
};


MultiGpuManager::Impl::Impl(): num_devices_(0)
{
    num_devices_ = getCudaEnabledDeviceCount();
    contexts_.resize(num_devices_);

    cuSafeCall(cuInit(0));

    CUdevice device;
    CUcontext prev_context;
    for (int i = 0; i < num_devices_; ++i)
    {
        cuSafeCall(cuDeviceGet(&device, i));
        cuSafeCall(cuCtxCreate(&contexts_[i], 0, device));
        cuSafeCall(cuCtxPopCurrent(&prev_context));
    }
}


MultiGpuManager::MultiGpuManager() {}
MultiGpuManager::~MultiGpuManager() {}


void MultiGpuManager::init()
{
    impl_ = Ptr<Impl>(new Impl());
}


void MultiGpuManager::gpuOn(int gpu_id)
{
    if (impl_.empty())
        CV_Error(CV_StsNullPtr, "MultiGpuManager::gpuOn: must be initialized before any calls");
    impl_->gpuOn(gpu_id);
}


void MultiGpuManager::gpuOff()
{
    if (impl_.empty())
        CV_Error(CV_StsNullPtr, "MultiGpuManager::gpuOff: must be initialized before any calls");
    impl_->gpuOff();
}

}}

#endif