/* ******************************************************************************
 *
 *
 * This program and the accompanying materials are made available under the
 * terms of the Apache License, Version 2.0 which is available at
 * https://www.apache.org/licenses/LICENSE-2.0.
 *
 *  See the NOTICE file distributed with this work for additional
 *  information regarding copyright ownership.
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 ******************************************************************************/

//
// @author Oleh Semeniv (oleg.semeniv@gmail.com)
//
#include <helpers/PointersManager.h>
#include <math/platformmath.h>
#include <math/templatemath.h>
#include <ops/declarable/helpers/updatersHelpers.h>
#include <system/op_boilerplate.h>

#include "execution/cuda/LaunchDims.h"
#include "helpers/DebugHelper.h"


namespace sd {
namespace ops {
namespace helpers {

///////////////////////////////////////////////////////////////////
template <typename T>
SD_KERNEL void rmsPropUpdaterCuda(const void *vx, const LongType *xShapeInfo, const void *vin,
                                  const LongType *inShapeInfo, void *vz, const LongType *zShapeInfo, void *vst,
                                  const LongType *stShapeInfo, const T lr, const T rmsDecay, const T epsilon) {
  const auto x = reinterpret_cast<const T *>(vx);
  const auto init = reinterpret_cast<const T *>(vin);
  auto up = reinterpret_cast<T *>(vz);
  auto st = reinterpret_cast<T *>(vst);

  __shared__ LongType xLen, xRank, zRank, inRank, stRank;
  __shared__ bool bOrdering, bXZsame, bXInSame, bXStSame;
  __shared__ LongType *sharedMem;
  __shared__ const LongType *xShape, *zShape, *inShape, *stShape;
  __shared__ const LongType *xStride, *zStride, *inStride, *stStride;

  if (threadIdx.x == 0) {
    extern __shared__ unsigned char shmem[];
    sharedMem = reinterpret_cast<LongType*>(shmem);

    xLen = shape::length(xShapeInfo);
    xRank = shape::rank(xShapeInfo);
    zRank = shape::rank(zShapeInfo);
    inRank = shape::rank(inShapeInfo);
    stRank = shape::rank(stShapeInfo);

    xShape = shape::shapeOf(xShapeInfo);
    xStride = shape::stride(xShapeInfo);
    zShape = shape::shapeOf(zShapeInfo);
    zStride = shape::stride(zShapeInfo);
    inShape = shape::shapeOf(inShapeInfo);
    inStride = shape::stride(inShapeInfo);
    stShape = shape::shapeOf(stShapeInfo);
    stStride = shape::stride(stShapeInfo);

    bOrdering = shape::order(zShapeInfo) == shape::order(xShapeInfo) &&
                shape::order(xShapeInfo) == shape::order(stShapeInfo) &&
                shape::order(xShapeInfo) == shape::order(inShapeInfo);
    bXZsame = shape::haveSameShapeAndStrides(xShapeInfo, zShapeInfo);
    bXInSame = shape::haveSameShapeAndStrides(xShapeInfo, inShapeInfo);
    bXStSame = shape::haveSameShapeAndStrides(xShapeInfo, stShapeInfo);
  }
  __syncthreads();

  LongType coords[SD_MAX_RANK];

  for (LongType i = blockIdx.x * blockDim.x + threadIdx.x; i < xLen; i += gridDim.x * blockDim.x) {
    LongType xOffset, zOffset, initOffset, stOffset;

    INDEX2COORDS(i, xRank, xShape, coords);
    COORDS2INDEX(xRank, xStride, coords, xOffset);

    if (bXZsame) {
      zOffset = xOffset;
    } else {
      COORDS2INDEX(zRank, zStride, coords, zOffset);
    }

    if (bXInSame) {
      initOffset = xOffset;
    } else {
      COORDS2INDEX(inRank, inStride, coords, initOffset);
    }

    if (bXStSame) {
      stOffset = xOffset;
    } else {
      COORDS2INDEX(stRank, stStride, coords, stOffset);
    }

    st[stOffset] = init[initOffset] * rmsDecay + x[xOffset] * x[xOffset] * (1 - rmsDecay);
    up[zOffset] = (lr * x[xOffset]) / (math::sd_sqrt<T, T>(st[stOffset]) + epsilon);
  }
}

///////////////////////////////////////////////////////////////////
template <typename T>
void rmsPropUpdaterCudaLauncher(const int blocksPerGrid, const int threadsPerBlock, const int sharedMemory,
                                const cudaStream_t *stream, const void *vx, const LongType *xShapeInfo,
                                const void *vin, const LongType *inShapeInfo, void *vz,
                                const LongType *zShapeInfo, void *vst, const LongType *stShapeInfo,
                                const double dLr, const double dRmsDecay, const double dEpsilon) {
  const T lr = static_cast<T>(dLr);
  const T rmsDecay = static_cast<T>(dRmsDecay);
  T epsilon = static_cast<T>(dEpsilon);
  //fp16 to prevent underflow
  if(epsilon == 0.0) {
    epsilon = static_cast<T>(1e-7);
  }
  rmsPropUpdaterCuda<T><<<blocksPerGrid, threadsPerBlock, sharedMemory, *stream>>>(
      vx, xShapeInfo, vin, inShapeInfo, vz, zShapeInfo, vst, stShapeInfo, lr, rmsDecay, epsilon);
  sd::DebugHelper::checkErrorCode(const_cast<cudaStream_t *>(stream), "rmsPropUpdaterCudaLauncher failed");

}

///////////////////////////////////////////////////////////////////
void updaterRmsProp(LaunchContext *context, NDArray&gradient, NDArray&initState, NDArray &update,
                    NDArray &stateG, const double dLr, const double dRmsDecay, const double dEpsilon) {
  PointersManager manager(context, "rmsPropUpdater");

  dim3 launchDims = updaterDims(gradient.lengthOf());
  NDArray::prepareSpecialUse({&update, &stateG}, {&gradient, &initState});

  BUILD_SINGLE_SELECTOR(
      gradient.dataType(), rmsPropUpdaterCudaLauncher,
      (launchDims.y, launchDims.x,launchDims.z, context->getCudaStream(), gradient.specialBuffer(), gradient.specialShapeInfo(),
       initState.specialBuffer(), initState.specialShapeInfo(), update.specialBuffer(), update.specialShapeInfo(),
       stateG.specialBuffer(), stateG.specialShapeInfo(), dLr, dRmsDecay, dEpsilon),
      SD_FLOAT_TYPES);

  NDArray::registerSpecialUse({&update, &stateG}, {&gradient, &initState});

  manager.synchronize();
}

}  // namespace helpers
}  // namespace ops
}  // namespace sd