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/*! \internal \file
 *
 * \brief Implements backend-specific functions of the update-constraints in SYCL.
 *
 * \author Artem Zhmurov <zhmurov@gmail.com>
 *
 * \ingroup module_mdlib
 */
#include "gmxpre.h"

#include "gromacs/gpu_utils/devicebuffer_sycl.h"
#include "gromacs/gpu_utils/gmxsycl.h"
#include "gromacs/gpu_utils/gputraits_sycl.h"
#include "gromacs/utility/gmxassert.h"

#include "update_constrain_gpu_internal.h"

//! \brief Class name for scaling kernel
class ScaleKernel;

namespace gmx
{

//! \brief Function returning the scaling kernel lambda.
static auto scaleKernel(sycl::handler&                                        cgh,
                        DeviceAccessor<Float3, sycl::access_mode::read_write> a_x,
                        const ScalingMatrix                                   scalingMatrix)
{
    a_x.bind(cgh);

    return [=](sycl::id<1> itemIdx) {
        Float3 x     = a_x[itemIdx];
        x[0]         = scalingMatrix.xx * x[0] + scalingMatrix.yx * x[1] + scalingMatrix.zx * x[2];
        x[1]         = scalingMatrix.yy * x[1] + scalingMatrix.zy * x[2];
        x[2]         = scalingMatrix.zz * x[2];
        a_x[itemIdx] = x;
    };
}

void launchScaleCoordinatesKernel(const int            numAtoms,
                                  DeviceBuffer<Float3> d_coordinates,
                                  const ScalingMatrix& mu,
                                  const DeviceStream&  deviceStream)
{
    const sycl::range<1> rangeAllAtoms(numAtoms);
    sycl::queue          queue = deviceStream.stream();

    sycl::event e = queue.submit([&](sycl::handler& cgh) {
        auto kernel = scaleKernel(cgh, d_coordinates, mu);
        cgh.parallel_for<ScaleKernel>(rangeAllAtoms, kernel);
    });
    // TODO: Although this only happens on the pressure coupling steps, this synchronization
    //       can affect the performance if nstpcouple is small. See Issue #4018
    e.wait_and_throw();
}

} // namespace gmx
