/*******************************************************************************
 * 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
 ******************************************************************************/

//
// Created by raver119 on 30.11.17.
//

#include <ops/declarable/helpers/col2im.h>

namespace nd4j {
namespace ops {
namespace helpers {

// [bS, iC, kH, kW, oH, oW] is de-convoluted to [bS, iC, iH, iW]
template <typename T>
void col2im_(nd4j::LaunchContext & context, const NDArray& input,  NDArray& output, const int sH, const int sW, const int pH, const int pW, const int iH, const int iW, const int dH, const int dW) {

    auto imBuff         = output.bufferAsT<T>();
	auto colBuff        = input.bufferAsT<T>();
	auto imShapeBuffer  = output.getShapeInfo();
	auto colShapeBuffer = input.getShapeInfo();
    auto colShape  		= shape::shapeOf(colShapeBuffer);
    auto colStride 		= shape::stride(colShapeBuffer);
    auto imShape  	    = shape::shapeOf(imShapeBuffer);
    auto imStride 	    = shape::stride(imShapeBuffer);            

    const int bS = imShape[0];
    const int iC = imShape[1];
    const int kH = colShape[2];
    const int kW = colShape[3];                    
    const int oH = colShape[4];
    const int oW = colShape[5];
    const Nd4jLong colStride0 = colStride[0];
    const Nd4jLong colStride1 = colStride[1];
    const Nd4jLong colStride2 = colStride[2];
    const Nd4jLong colStride3 = colStride[3];
    const Nd4jLong colStride4 = colStride[4];
    const Nd4jLong colStride5 = colStride[5];
    const Nd4jLong imStride0  = imStride[0];
    const Nd4jLong imStride1  = imStride[1];
    const Nd4jLong imStride2  = imStride[2];
    const Nd4jLong imStride3  = imStride[3];
        
    memset(imBuff, 0, shape::length(imShapeBuffer) * sizeof(T));

	T *col, *im;
    int imRow, imCol;

    // if (shape::order(colShapeBuffer) == 'c' &&  shape::order(imShapeBuffer) == 'c' && shape::strideDescendingCAscendingF(colShapeBuffer) && shape::strideDescendingCAscendingF(imShapeBuffer)) {
    if (false) {

        PRAGMA_OMP_PARALLEL_FOR_SIMD_ARGS(private(col, im, imRow, imCol) collapse(2))
    	for (int b = 0; b < bS; b++) {
      		for (int c = 0; c < iC; ++c) {                    
            	for (int kRow = 0; kRow < kH; ++kRow) {                        
                	for (int kCol = 0; kCol < kW; ++kCol) {                            
                    	for (int colH = 0; colH < oH; ++colH) {
                        	for (int colW = 0; colW < oW; ++colW) {                    

                            	imRow = (-pH + kRow * dH) + colH*sH;
                                imCol = (-pW + kCol * dW) + colW*sW;

                                col = colBuff + b*colStride0 + c*colStride1 + kRow*colStride2 + kCol*colStride3 + colH*colStride4 + colW*colStride5;
                                im  = imBuff  + b*imStride0  + c*imStride1  + imRow*imStride2 + imCol*imStride3;

                                if (static_cast<unsigned>(imRow) < static_cast<unsigned>(iH) && static_cast<unsigned>(imCol) < static_cast<unsigned>(iW))
                                	*im += *col;
                            }
                        }
                    }
                }
            }
        }  
    }
    else {

        PRAGMA_OMP_PARALLEL_FOR_SIMD_ARGS(firstprivate(imRow, imCol))
    	for (int b = 0; b < bS; ++b) {
            T* im0  = imBuff + b*imStride0;
            T* col4 = colBuff + b*colStride0;
        	for (int colH = 0; colH < oH; ++colH, col4 += colStride4) {
                T* col5 = col4;
            	for (int colW = 0; colW < oW; ++colW, col5 += colStride5) {
                    T* col1 = col5;
                    T* im1 = im0;
                	for (int c = 0; c < iC; ++c, col1 += colStride1, im1 += imStride1) {
                        int imRow = (-pH + colH*sH);
                        T* col2 = col1;
                        T* im2 = im1 + imRow*imStride2;
                    	for (int kRow = 0; kRow < kH; ++kRow, col2 += colStride2, imRow += dH, im2 += dH*imStride2) {
                            int imCol =-pW + colW*sW;
                            T* col3 = col2;                            
                            T* im3 = im2 + imCol*imStride3;
                        	for (int kCol = 0; kCol < kW; ++kCol, col3 += colStride3, imCol += dW, im3 += dW*imStride3) {

                                if (static_cast<unsigned>(imRow) < static_cast<unsigned>(iH) && static_cast<unsigned>(imCol) < static_cast<unsigned>(iW))
                                	*im3 += *col3;
                            }
                        }
                    }
                }                           
            }
        }  
    }
}


void col2im(nd4j::LaunchContext & context, const NDArray& input,  NDArray& output, const int sH, const int sW, const int pH, const int pW, const int iH, const int iW, const int dH, const int dW) {
	BUILD_SINGLE_SELECTOR(input.dataType(), col2im_, (context, input, output, sH, sW, pH, pW, iH, iW, dH, dW), FLOAT_TYPES);
}

}
}
}