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#include "../precomp.hpp"
#include "layers_common.hpp"
#include <algorithm>
#include <stdlib.h>
using std::max;

namespace cv
{
namespace dnn
{

class SoftMaxLayerImpl : public SoftmaxLayer
{
public:

    SoftMaxLayerImpl(const LayerParams& params)
    {
        axisRaw = params.get<int>("axis", 1);
        setParamsFrom(params);
    }

    bool getMemoryShapes(const std::vector<MatShape> &inputs,
                         const int requiredOutputs,
                         std::vector<MatShape> &outputs,
                         std::vector<MatShape> &internals) const
    {
        bool inplace = Layer::getMemoryShapes(inputs, requiredOutputs, outputs, internals);
        MatShape shape = inputs[0];
        int cAxis = clamp(axisRaw, shape.size());
        shape[cAxis] = 1;
        internals.assign(1, shape);
        return inplace;
    }

    void forward(std::vector<Mat*> &inputs, std::vector<Mat> &outputs, std::vector<Mat> &internals)
    {
        const Mat &src = *inputs[0];
        Mat &dst = outputs[0];

        int axis = clamp(axisRaw, src.dims);
        size_t outerSize = src.total(0, axis), channels = src.size[axis],
                innerSize = src.total(axis + 1);

        CV_Assert(src.type() == CV_32F);
        CV_Assert(src.isContinuous() && dst.isContinuous());

        const float *srcPtr = src.ptr<float>();
        float *dstPtr = dst.ptr<float>();
        float *bufPtr = internals[0].ptr<float>();

        size_t outerStep = src.total(axis);
        size_t cnStep = src.total(axis + 1);

        //compute max along axis
        for (size_t outerDim = 0; outerDim < outerSize; outerDim++)
        {
            size_t srcOffset = outerDim * outerStep;
            size_t bufOffset = outerDim * cnStep;

            memcpy(bufPtr + bufOffset, srcPtr + srcOffset, innerSize * sizeof(float));

            for (size_t cnDim = 1; cnDim < channels; cnDim++)
            {
                for (size_t i = 0; i < innerSize; i++)
                    bufPtr[bufOffset + i] = std::max(bufPtr[bufOffset + i], srcPtr[srcOffset + cnDim * cnStep + i]);
            }
        }

        //subtract max
        for (size_t outerDim = 0; outerDim < outerSize; outerDim++)
        {
            size_t srcOffset = outerDim * outerStep;
            size_t bufOffset = outerDim * cnStep;

            for (size_t cnDim = 0; cnDim < channels; cnDim++)
            {
                for (size_t i = 0; i < innerSize; i++)
                    dstPtr[srcOffset + cnDim * cnStep + i] = srcPtr[srcOffset + cnDim * cnStep + i] - bufPtr[bufOffset + i];
            }
        }

        cv::exp(dst, dst);

        for (size_t outerDim = 0; outerDim < outerSize; outerDim++)
        {
            size_t srcOffset = outerDim * outerStep;
            size_t bufOffset = outerDim * cnStep;

            //sum exp along axis
            for (size_t i = 0; i < innerSize; i++)
                bufPtr[bufOffset + i] = 0.f;

            for (size_t cnDim = 0; cnDim < channels; cnDim++)
            {
                for (size_t i = 0; i < innerSize; i++)
                    bufPtr[bufOffset + i] += dstPtr[srcOffset + cnDim * cnStep + i];
            }

            //divide by computed sum
            for (size_t cnDim = 0; cnDim < channels; cnDim++)
            {
                for (size_t i = 0; i < innerSize; i++)
                    dstPtr[srcOffset + cnDim * cnStep + i] /= bufPtr[bufOffset + i];
            }
        }
    }

    int axisRaw;
};

Ptr<SoftmaxLayer> SoftmaxLayer::create(const LayerParams& params)
{
    return Ptr<SoftmaxLayer>(new SoftMaxLayerImpl(params));
}

}
}