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/*! \libinternal \file
 *  \brief Implements a GpuEventSynchronizer class for CUDA.
 *
 *  \author Aleksei Iupinov <a.yupinov@gmail.com>
 *  \inlibraryapi
 */
#ifndef GMX_GPU_UTILS_GPUEVENTSYNCHRONIZER_CUH
#define GMX_GPU_UTILS_GPUEVENTSYNCHRONIZER_CUH

#include "gromacs/gpu_utils/cudautils.cuh"
#include "gromacs/gpu_utils/device_stream.h"
#include "gromacs/gpu_utils/gputraits.cuh"
#include "gromacs/utility/gmxassert.h"

#ifndef DOXYGEN

/*! \libinternal \brief
 * A class which allows for CPU thread to mark and wait for certain GPU stream execution point.
 * The event can be put into the stream with markEvent() and then later waited on with waitForEvent().
 * This can be repeated as necessary, but the current implementation does not allow waiting on
 * completed event more than once, expecting only exact pairs of markEvent(stream); waitForEvent().
 * The class generally attempts to track the correctness of its state transitions, but
 * please note that calling waitForEvent() right after the construction will succeed with CUDA but fail with OpenCL.
 *
 * Another possible mode of operation can be implemented if needed:
 * multiple calls to waitForEvent() after a single markEvent().
 * For this, only some small alterations to gpueventsynchronizer_ocl.h need to be made.
 * This was tested to work both with CUDA and NVidia OpenCL, but not with AMD/Intel OpenCL.
 */
class GpuEventSynchronizer
{
public:
    GpuEventSynchronizer()
    {
        cudaError_t gmx_used_in_debug stat = cudaEventCreateWithFlags(&event_, cudaEventDisableTiming);
        GMX_RELEASE_ASSERT(stat == cudaSuccess,
                           ("cudaEventCreate failed. " + gmx::getDeviceErrorString(stat)).c_str());
    }
    ~GpuEventSynchronizer()
    {
        cudaError_t gmx_used_in_debug stat = cudaEventDestroy(event_);
        GMX_RELEASE_ASSERT(stat == cudaSuccess,
                           ("cudaEventDestroy failed. " + gmx::getDeviceErrorString(stat)).c_str());
    }
    //! No copying
    GpuEventSynchronizer(const GpuEventSynchronizer&) = delete;
    //! No assignment
    GpuEventSynchronizer& operator=(GpuEventSynchronizer&&) = delete;
    //! Moving is disabled but can be considered in the future if needed
    GpuEventSynchronizer(GpuEventSynchronizer&&) = delete;

    /*! \brief Marks the synchronization point in the \p stream.
     * Should be followed by waitForEvent().
     */
    inline void markEvent(const DeviceStream& deviceStream)
    {
        cudaError_t gmx_used_in_debug stat = cudaEventRecord(event_, deviceStream.stream());
        GMX_ASSERT(stat == cudaSuccess,
                   ("cudaEventRecord failed. " + gmx::getDeviceErrorString(stat)).c_str());
    }
    /*! \brief Synchronizes the host thread on the marked event. */
    inline void waitForEvent()
    {
        cudaError_t gmx_used_in_debug stat = cudaEventSynchronize(event_);
        GMX_ASSERT(stat == cudaSuccess,
                   ("cudaEventSynchronize failed. " + gmx::getDeviceErrorString(stat)).c_str());
    }
    /*! \brief Enqueues a wait for the recorded event in stream \p stream */
    inline void enqueueWaitEvent(const DeviceStream& deviceStream)
    {
        cudaError_t gmx_used_in_debug stat = cudaStreamWaitEvent(deviceStream.stream(), event_, 0);
        GMX_ASSERT(stat == cudaSuccess,
                   ("cudaStreamWaitEvent failed. " + gmx::getDeviceErrorString(stat)).c_str());
    }

private:
    cudaEvent_t event_;
};

#endif

#endif
