/*******************************************************************************
 * Copyright (c) 2015-2018 Skymind, Inc.
 *
 * 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.
 *
 * 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 raver119@gmail.com
// @author Yurii Shyrma (iuriish@yahoo.com)
//

#include <ops/declarable/helpers/lrn.h>
#include <Status.h>
#include <ConstantTadHelper.h>
#include <execution/Threads.h>

namespace nd4j {
namespace ops {
namespace helpers {

template <typename T>
static int lrnFunctor_(nd4j::graph::Context& block, NDArray* input, NDArray* output, int depth, float bias, float alpha, float beta) {

    nd4j_debug("MKL-DNN is not used for lrn!\n", 0);

    const int rank = input->rankOf();

    TadPack inTadPack = nd4j::ConstantTadHelper::getInstance()->tadForDimensions(input->getShapeInfo(), {rank - 1});
    TadPack outTadPack;

    if(shape::haveSameShapeAndStrides(input->getShapeInfo(), output->getShapeInfo()))
        outTadPack = inTadPack;
    else
        outTadPack = nd4j::ConstantTadHelper::getInstance()->tadForDimensions(output->getShapeInfo(), {rank - 1});

    const Nd4jLong numOfTads = inTadPack.numberOfTads();
    const Nd4jLong tadLen    = input->sizeAt(-1); 
    
    const Nd4jLong* inTadOffsets    = inTadPack.primaryOffsets();        
    const Nd4jLong* outTadOffsets = outTadPack.primaryOffsets();

    const Nd4jLong inTadEws    = shape::elementWiseStride(inTadPack.primaryShapeInfo());
    const Nd4jLong outTadEws = shape::elementWiseStride(outTadPack.primaryShapeInfo());
    
    const T* inBuff  = reinterpret_cast<T*>(input->getBuffer());
          T* outBuff = reinterpret_cast<T*>(output->getBuffer());

    const T tbias  = static_cast<T>(bias);
    const T tbeta  = static_cast<T>(beta);
    const T talpha = static_cast<T>(alpha);    

    if(inTadEws == 1 && outTadEws == 1) {
        
        auto func = PRAGMA_THREADS_FOR {
            for (auto i = start; i < stop; i++) {
                const T *x = inBuff + inTadOffsets[i];
                T *y = outBuff + outTadOffsets[i];

                T prev = 0;

                // calculate squared sum of elements per each j-th element range [j - depth, j + depth + 1]
                // we store each squared sum in corresponding element of y array
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    if (j == 0) {
                        for (uint s = begin; s < end; ++s)
                            prev = prev + x[s] * x[s];
                        y[j] = prev;
                    } else if (begin == 0 && last <= tadLen)
                        y[j] = prev + x[end - 1] * x[end - 1];
                    else if (begin > 0 && last <= tadLen)
                        y[j] = prev + x[end - 1] * x[end - 1] - x[begin - 1] * x[begin - 1];
                    else if (begin > 0 && last > tadLen)
                        y[j] = prev - x[begin - 1] * x[begin - 1];
                    else
                        y[j] = prev;

                    if (j != 0)
                        prev = y[j];

                    y[j] = x[j] / nd4j::math::nd4j_pow<T, T, T>(tbias + alpha * prev, tbeta);
                }
            }
        };

        samediff::Threads::parallel_tad(func, 0, numOfTads);
    }
    else {
        auto func = PRAGMA_THREADS_FOR {
            for (Nd4jLong i = 0; i < numOfTads; ++i) {
                const T *x = inBuff + inTadOffsets[i];
                T *y = outBuff + outTadOffsets[i];

                T prev = 0;

                // calculate squared sum of elements per each j-th element range [j - depth, j + depth + 1]
                // we store each squared sum in corresponding element of y array
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    if (j == 0) {
                        for (uint s = begin; s < end; ++s)
                            prev = prev + x[s * inTadEws] * x[s * inTadEws];
                        y[j * outTadEws] = prev;
                    } else if (begin == 0 && last <= tadLen)
                        y[j * outTadEws] = prev + x[(end - 1) * inTadEws] * x[(end - 1) * inTadEws];
                    else if (begin > 0 && last <= tadLen)
                        y[j * outTadEws] = prev + x[(end - 1) * inTadEws] * x[(end - 1) * inTadEws] - x[(begin - 1) * inTadEws] * x[(begin - 1) * inTadEws];
                    else if (begin > 0 && last > tadLen)
                        y[j * outTadEws] = prev - x[(begin - 1) * inTadEws] * x[(begin - 1) * inTadEws];
                    else
                        y[j * outTadEws] = prev;

                    if (j != 0)
                        prev = y[j * outTadEws];

                    y[j * outTadEws] = x[j * inTadEws] / nd4j::math::nd4j_pow<T, T, T>(tbias + alpha * prev, tbeta);
                }
            }
        };

        samediff::Threads::parallel_tad(func, 0, numOfTads);
    }    
    return Status::OK();
}
    
BUILD_SINGLE_TEMPLATE(template int lrnFunctor_, (nd4j::graph::Context& block, NDArray* input, NDArray* output, int depth, float bias, float alpha, float beta), FLOAT_TYPES);

int lrnFunctor(nd4j::graph::Context& block, NDArray* input, NDArray* output, int depth, double bias, double alpha, double beta) {
    BUILD_SINGLE_SELECTOR(input->dataType(), return lrnFunctor_, (block, input, output, depth, bias, alpha, beta), FLOAT_TYPES);
}

//////////////////////////////////////////////////////////////////////////
template <typename X, typename Y>
static void lrnBP_(const NDArray& input, const NDArray& gradO, NDArray& gradI, const int depth, const float bias, const float alpha, const float beta) {
    
    const int rank = input.rankOf();

    TadPack inTadPack = nd4j::ConstantTadHelper::getInstance()->tadForDimensions(input.getShapeInfo(), {rank - 1});
    TadPack gradITadPack;

    if(shape::haveSameShapeAndStrides(input.getShapeInfo(), gradI.getShapeInfo()))
        gradITadPack = inTadPack;
    else
        gradITadPack = nd4j::ConstantTadHelper::getInstance()->tadForDimensions(gradI.getShapeInfo(), {rank - 1});

    const Nd4jLong numOfTads = inTadPack.numberOfTads();
    const Nd4jLong tadLen    = input.sizeAt(-1); 
    
    const Nd4jLong* inTadOffsets    = inTadPack.primaryOffsets();        
    const Nd4jLong* gradITadOffsets = gradITadPack.primaryOffsets();

    const Nd4jLong inTadEws    = shape::elementWiseStride(inTadPack.primaryShapeInfo());
    const Nd4jLong gradITadEws = shape::elementWiseStride(gradITadPack.primaryShapeInfo());
    
    const X* inBuff    = reinterpret_cast<X*>(input.getBuffer());
          Y* gradIBuff = reinterpret_cast<Y*>(gradI.getBuffer());    

    const Y tbias  = static_cast<Y>(bias);
    const Y tbeta  = static_cast<Y>(beta);
    const Y talpha = static_cast<Y>(alpha);
    const Y coeff  = talpha * tbeta; 

    if(inTadEws == 1 && gradITadEws == 1) {
        
        auto func = PRAGMA_THREADS_FOR {
            for (auto i = start; i < stop; i++) {
                const X *x = inBuff + inTadOffsets[i];
                      Y *y = gradIBuff + gradITadOffsets[i];

                // this loop calculates squared sum of elements per each j-th element range [j - depth, j + depth + 1]
                // we store each squared sum in corresponding element of y array
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    if (j == 0) {
                        y[0] = 0;
                        for (uint s = begin; s < end; ++s)
                            y[0] = y[0] + x[s] * x[s];
                    } else if (begin == 0 && last <= tadLen)
                        y[j] = y[j - 1] + x[end - 1] * x[end - 1];
                    else if (begin > 0 && last <= tadLen)
                        y[j] = y[j - 1] + x[end - 1] * x[end - 1] - x[begin - 1] * x[begin - 1];
                    else if (begin > 0 && last > tadLen)
                        y[j] = y[j - 1] - x[begin - 1] * x[begin - 1];
                    else
                        y[j] = y[j - 1];
                }

                Y *factor = new Y[tadLen];

                Y prev = 0;
                // second loop calculates derivatives using information gained in first loop above
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    Y init = tbias + talpha * y[j];

                    if (j == 0) {
                        for (uint s = begin; s < end; ++s) {
                            factor[s] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[s], -tbeta - 1);
                            prev = prev + x[s] * factor[s];
                        }
                        y[0] = prev;
                    } else if (begin == 0 && last <= tadLen) {
                        factor[end - 1] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[end - 1], -tbeta - 1);
                        y[j] = prev + x[end - 1] * factor[end - 1];
                    } else if (begin > 0 && last <= tadLen) {
                        factor[end - 1] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[end - 1], -tbeta - 1);
                        y[j] = prev + x[end - 1] * factor[end - 1] - x[begin - 1] * factor[begin - 1];
                    } else if (begin > 0 && last > tadLen)
                        y[j] = prev - x[begin - 1] * factor[begin - 1];
                    else
                        y[j] = prev;

                    if (j != 0)
                        prev = y[j];

                    y[j] = factor[j] * init - 2 * x[j] * coeff * prev;
                }

                delete[]factor;
            }
        };

        samediff::Threads::parallel_tad(func, 0, numOfTads);
    }
    else {

        auto func = PRAGMA_THREADS_FOR {
            for (auto i = start; i < stop; i++) {
                const X *x = inBuff + inTadOffsets[i];
                      Y *y = gradIBuff + gradITadOffsets[i];

                // this loop calculates squared sum of elements per each j-th element range [j - depth, j + depth + 1]
                // we store each squared sum in corresponding element of y array
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    if (j == 0) {
                        y[0] = 0;
                        for (uint s = begin; s < end; ++s)
                            y[0] = y[0] + x[s * inTadEws] * x[s * inTadEws];
                    } else if (begin == 0 && last <= tadLen)
                        y[j * gradITadEws] =
                                y[(j - 1) * gradITadEws] + x[(end - 1) * inTadEws] * x[(end - 1) * inTadEws];
                    else if (begin > 0 && last <= tadLen)
                        y[j * gradITadEws] =
                                y[(j - 1) * gradITadEws] + x[(end - 1) * inTadEws] * x[(end - 1) * inTadEws] -
                                x[(begin - 1) * inTadEws] * x[(begin - 1) * inTadEws];
                    else if (begin > 0 && last > tadLen)
                        y[j * gradITadEws] =
                                y[(j - 1) * gradITadEws] - x[(begin - 1) * inTadEws] * x[(begin - 1) * inTadEws];
                    else
                        y[j * gradITadEws] = y[(j - 1) * gradITadEws];
                }

                Y *factor = new Y[tadLen];

                Y prev = 0;
                // second loop calculates derivatives using information gained in first loop above
                for (Nd4jLong j = 0; j < tadLen; ++j) {
                    const uint begin = nd4j::math::nd4j_max<int>(0, j - depth);
                    const uint last = depth + j + 1;
                    const uint end = nd4j::math::nd4j_min<int>(last, tadLen);

                    Y init = tbias + talpha * y[j * gradITadEws];

                    if (j == 0) {
                        for (uint s = begin; s < end; ++s) {
                            factor[s] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[s * gradITadEws], -tbeta - 1);
                            prev = prev + x[s * inTadEws] * factor[s];
                        }
                        y[0] = prev;
                    } else if (begin == 0 && last <= tadLen) {
                        factor[end - 1] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[(end - 1) * gradITadEws],
                                                                        -tbeta - 1);
                        y[j * gradITadEws] = prev + x[(end - 1) * inTadEws] * factor[end - 1];
                    } else if (begin > 0 && last <= tadLen) {
                        factor[end - 1] = nd4j::math::nd4j_pow<Y, Y, Y>(tbias + talpha * y[(end - 1) * gradITadEws],
                                                                        -tbeta - 1);
                        y[j * gradITadEws] = prev + x[(end - 1) * inTadEws] * factor[end - 1] -
                                             x[(begin - 1) * inTadEws] * factor[begin - 1];
                    } else if (begin > 0 && last > tadLen)
                        y[j * gradITadEws] = prev - x[(begin - 1) * inTadEws] * factor[begin - 1];
                    else
                        y[j * gradITadEws] = prev;

                    if (j != 0)
                        prev = y[j * gradITadEws];

                    y[j * gradITadEws] = factor[j] * init - 2 * x[j * inTadEws] * coeff * prev;
                }

                delete[]factor;
            }
        };

        samediff::Threads::parallel_tad(func, 0, numOfTads);
    }    
    gradI *= gradO;
}


void lrnBP(nd4j::graph::Context& block, const NDArray& input, const NDArray& gradO, NDArray& gradI, const int depth, const float bias, const float alpha, const float beta) {
    BUILD_DOUBLE_SELECTOR(input.dataType(), gradO.dataType(), lrnBP_, (input, gradO, gradI, depth, bias, alpha, beta), FLOAT_TYPES, FLOAT_TYPES);
}

}
}
}