/*******************************************************************************
 * 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, created on 29/10/17.
// @author Yurii Shyrma (iuriish@yahoo.com)
//

#include <op_boilerplate.h>
#if NOT_EXCLUDED(OP_batchnorm)

#include <ops/declarable/CustomOperations.h>
#include<ops/declarable/helpers/batchnorm.h>

namespace nd4j {
namespace ops {


//////////////////////////////////////////////////////////////////////////
CUSTOM_OP_IMPL(batchnorm, 3, 1, false, 1, 2) {

    auto input    = INPUT_VARIABLE(0);
    auto mean     = INPUT_VARIABLE(1);
    auto variance = INPUT_VARIABLE(2);
    NDArray* gamma    = nullptr;
    NDArray* beta     = nullptr;

    auto output   = OUTPUT_VARIABLE(0);

    const bool   applyScale  = (bool)INT_ARG(0);
    const bool   applyOffset = (bool)INT_ARG(1);
    const double epsilon     = T_ARG(0);

    if(applyScale)
        gamma = INPUT_VARIABLE(3);
    if(applyOffset)
        beta = INPUT_VARIABLE(3 + (int)applyScale);

    const int numOfIntArgs = block.getIArguments()->size();
    const int inRank = input->rankOf();

    // get axes args to normalize input array over
    std::vector<int> axes;
    if(numOfIntArgs > 2)
        for(int i = 2; i < numOfIntArgs; ++i)
            axes.push_back(INT_ARG(i));
    else
        axes.push_back(inRank-1);               // default dimension to reduce along is last dimension

    const int numOfAxes = axes.size();
    REQUIRE_TRUE(numOfAxes <= inRank, 0, "BATCHNORM op: too big number of input axes to normalize over, expected number should be less or equal to rank of input array, but got %i and %i correspondingly !", numOfAxes, inRank);

    // evaluate expected shape for mean, variance and gamma. These 3 arrays should have identical shapes
    // for example if input shape is {2,3,4,5,6} and axes = {1,3}, then expected shape would be {1,3,1,5,1}, and if axes = {3}, then expected shape would be {5}
    std::vector<Nd4jLong> expShape;
    if(numOfAxes == 1)
        expShape.push_back(input->sizeAt(axes[0]));
    else {      // get, for example, something like {1, inputDim1, 1, inputDim3, 1} if axes = {1, 3}
        expShape = std::vector<Nd4jLong>(inRank, 1);
        for(uint i = 0; i < numOfAxes; ++i)
            expShape[axes[i]] = input->sizeAt(axes[i]);
    }

    REQUIRE_TRUE(mean->isSameShape(expShape) , 0, "BATCHNORM op: wrong shape of mean array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(mean).c_str());
    REQUIRE_TRUE(variance->isSameShape(expShape), 0, "BATCHNORM op: wrong shape of variance array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(variance).c_str());
    if(gamma)
        REQUIRE_TRUE(gamma->isSameShape(expShape), 0, "BATCHNORM op: wrong shape of gamma array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(gamma).c_str());
    if(beta)
        REQUIRE_TRUE(beta->isSameShape(expShape), 0, "BATCHNORM op: wrong shape of beta array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(beta).c_str());

    // types of all input arrays should be the same
    for(int i = 1; i < block.width(); ++i)
        REQUIRE_TRUE(INPUT_VARIABLE(0)->dataType() == INPUT_VARIABLE(i)->dataType(), 0, "BATCHNORM op: types of all input arrays should be the same !");

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

    // formula: output = gamma * ((input - mean) / sqrt(variance + epsilon)) + beta
    helpers::batchnorm(input, mean, variance, gamma, beta, output, axes, epsilon);

    return Status::OK();
}

DECLARE_TYPES(batchnorm) {
    getOpDescriptor()->setAllowedInputTypes({ALL_FLOATS})->setSameMode(true);
}

DECLARE_SHAPE_FN(batchnorm) {

    auto inShapeInfo = inputShape->at(0);
    DataType outType = DataTypeUtils::pickFloatingType(ArrayOptions::dataType(inShapeInfo));

    auto outShapeInfo = ShapeBuilders::copyShapeInfoAndType(inShapeInfo, outType, false, block.getWorkspace());    // output shape is identical to input shape

    return SHAPELIST(CONSTANT(outShapeInfo));
}

//////////////////////////////////////////////////////////////////////////
CUSTOM_OP_IMPL(batchnorm_bp, 4, 3, false, 1, 2) {

    NDArray* input    = INPUT_VARIABLE(0);
    NDArray* mean     = INPUT_VARIABLE(1);
    NDArray* variance = INPUT_VARIABLE(2);
    NDArray* dLdO     = INPUT_VARIABLE(3);    // next epsilon
    NDArray* gamma    = nullptr;
    NDArray* beta     = nullptr;


    NDArray* dLdI = OUTPUT_VARIABLE(0);
    NDArray* dLdM = OUTPUT_VARIABLE(1);
    NDArray* dLdV = OUTPUT_VARIABLE(2);
    NDArray* dLdG = nullptr;
    NDArray* dLdB = nullptr;

    const bool   applyScale  = (bool)INT_ARG(0);
    const bool   applyOffset = (bool)INT_ARG(1);
    const float  epsilon     = T_ARG(0);

    if(applyScale) {
        gamma = INPUT_VARIABLE(4);
        dLdG  = OUTPUT_VARIABLE(3);
    }
    if(applyOffset) {
        beta = INPUT_VARIABLE(4 + (int)applyScale);
        dLdB = OUTPUT_VARIABLE(3 + (int)applyScale);
    }

    const int numOfIntArgs = block.getIArguments()->size();
    const int inRank = input->rankOf();

    // get axes args to normalize input array over
    std::vector<int> axes;
    if(numOfIntArgs > 2)
        for(int i = 2; i < numOfIntArgs; ++i)
            axes.push_back(INT_ARG(i));
    else
        axes.push_back(inRank-1);               // default dimension to reduce along is last dimension

    const int numOfAxes = axes.size();
    REQUIRE_TRUE(numOfAxes <= inRank, 0, "BATCHNORM_BP op: too big number of input axes to normalize over, expected number should be less or equal to rank of input array, but got %i and %i correspondingly !", numOfAxes, inRank);

    // evaluate expected shape for mean, variance and gamma. These 3 arrays should have identical shapes
    // for example if input shape is {2,3,4,5,6} and axes = {1,3}, then expected shape would be {1,3,1,5,1}, and if axes = {3}, then expected shape would be {5}
    std::vector<Nd4jLong> expShape;
    if(numOfAxes == 1)
        expShape.push_back(input->sizeAt(axes[0]));
    else {      // get, for example, something like {1, inputDim1, 1, inputDim3, 1} if axes = {1, 3}
        expShape = std::vector<Nd4jLong>(inRank, 1);
        for(uint i = 0; i < numOfAxes; ++i)
            expShape[axes[i]] = input->sizeAt(axes[i]);
    }

    REQUIRE_TRUE(mean->isSameShape(expShape), 0, "BATCHNORM_BP op: wrong shape of mean array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(mean).c_str());
    REQUIRE_TRUE(variance->isSameShape(expShape), 0, "BATCHNORM_BP op: wrong shape of variance array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(variance).c_str());
    if(gamma)
        REQUIRE_TRUE(gamma->isSameShape(expShape), 0, "BATCHNORM_BP op: wrong shape of gamma array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(gamma).c_str());
    if(beta)
        REQUIRE_TRUE(beta->isSameShape(expShape), 0, "BATCHNORM_BP op: wrong shape of beta array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(expShape).c_str(), ShapeUtils::shapeAsString(beta).c_str());

    REQUIRE_TRUE(input->isSameShape(dLdO), 0, "BATCHNORM_BP op: wrong shape of output gradients array, expected is %s, but got %s instead !", ShapeUtils::shapeAsString(input).c_str(), ShapeUtils::shapeAsString(dLdO).c_str());

    // types of all input arrays should be the same (except dLdO)
    for(int i = 1; i < block.width() - 1; ++i)
        if(i != 3)
            REQUIRE_TRUE(INPUT_VARIABLE(0)->dataType() == INPUT_VARIABLE(i)->dataType(), 0, "BATCHNORM_BP op: types of arrays (input, mean, variance, gamma, beta) should be the same !");

    // ***** calculations ***** //

    // formula for forward step: output = gamma * ((input - mean) / sqrt(variance + epsilon)) + beta

    // consider mean and variance as constants (since we get them as inputs and don't calculate them)
    // dLdI = (dLdO * gamma) / (variance + epsilon)^0.5
    // dLdV = (-0.5  * gamma * (dLdO * (x - mean))_sum) / (variance + epsilon)^1.5
    // dLdM = - (dLdO_sum * gamma) / (variance + epsilon)^0.5
    // dLdG = (dLdO * (x - mean))_sum / (variance + epsilon)^0.5
    // dLdB = dLdO_sum

    const auto excludedAxes = ShapeUtils::evalDimsToExclude(inRank, axes);

    NDArray temp1 = *variance + epsilon;
    temp1.applyTransform(transform::Reciprocal);            // 1 / (variance + epsilon)
    auto temp2 = temp1.transform(transform::Sqrt);     // 1 / (variance + epsilon)^0.5
    if(applyScale)
        temp2 *= *gamma;                                    // gamma / (variance + epsilon)^0.5

    NDArray temp3(input); // empty array with same shape as input
    input->applyBroadcast(nd4j::broadcast::Subtract, axes, mean, &temp3);  // input - mean
    temp3 *= *dLdO;                                                        // (input - mean) * dLdO

    const bool keepUnitiesInShape = inRank == mean->rankOf();

    // dLdI
    dLdO->applyBroadcast(nd4j::broadcast::Multiply, axes, &temp2, dLdI);

    // dLdM
    dLdO->reduceAlongDimension(reduce::Sum, dLdM, excludedAxes, keepUnitiesInShape);    // dLdO sum over excluded axes

    // dLdB
    if(applyOffset)
        dLdB->assign(dLdM);

    // dLdM
    // dLdM->applyPairwiseTransform(nd4j::pairwise::Multiply, temp2);
    // dLdM->applyTransform(nd4j::transform::Neg);
    *dLdM = 0;      // put zeros so far

    //dLdV
    temp3.reduceAlongDimension(reduce::Sum, dLdV, excludedAxes, keepUnitiesInShape);     // ((input - mean) * dLdO)_sum

    // dLdG
    if(applyScale) {
        dLdV->applyPairwiseTransform(nd4j::pairwise::Multiply, &temp2, dLdG);
        // dLdV->assign(dLdG);
        dLdG->applyPairwiseTransform(nd4j::pairwise::Divide, *gamma);
    }
    else
        // dLdV->applyPairwiseTransform(nd4j::pairwise::Multiply, temp2);

    // dLdV
    // dLdV->applyPairwiseTransform(nd4j::pairwise::Multiply, temp1);
    // *dLdV *= -0.5;
    *dLdV = 0;      // put zeros so far

    return Status::OK();
}

DECLARE_TYPES(batchnorm_bp) {
    getOpDescriptor()
            ->setAllowedInputTypes(0, nd4j::DataType::ANY)
            ->setAllowedInputTypes(1, nd4j::DataType::ANY)
            ->setAllowedInputTypes(2, nd4j::DataType::ANY)
            ->setAllowedInputTypes(3, {ALL_FLOATS})
            ->setAllowedInputTypes(4, nd4j::DataType::ANY)
            ->setAllowedInputTypes(5, nd4j::DataType::ANY)
            ->setAllowedOutputTypes({ALL_FLOATS});
}

//////////////////////////////////////////////////////////////////////////

DECLARE_SHAPE_FN(batchnorm_bp) {

    Nd4jLong* inShapeInfo   = inputShape->at(0);
    Nd4jLong* meanShapeInfo = inputShape->at(1);

    const bool applyScale  = (bool)INT_ARG(0);
    const bool applyOffset = (bool)INT_ARG(1);

    DataType outType = DataTypeUtils::pickFloatingType(ArrayOptions::dataType(inShapeInfo));

    auto shapes = SHAPELIST();

    // dLdI shapeInfo
    shapes->push_back(ConstantShapeHelper::getInstance()->createShapeInfo(outType, inShapeInfo));

    // dLdM shapeInfo
    shapes->push_back(ConstantShapeHelper::getInstance()->createShapeInfo(outType, meanShapeInfo));

    // dLdV shapeInfo (same as dLdM)
    shapes->push_back(shapes->at(shapes->size()-1));

    // dLdG shapeInfo (same as dLdM)
    if(applyScale)
        shapes->push_back(shapes->at(shapes->size()-1));

    // dLdB shapeInfo (same as dLdM)
    if(applyOffset)
        shapes->push_back(shapes->at(shapes->size()-1));

    return shapes;
}


}
}

#endif