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

// File:        reconfig.cpp

// Description: Network layer that reconfigures the scaling vs feature

//              depth.

// Author:      Ray Smith

//

// (C) Copyright 2014, Google Inc.

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

// http://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.

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

#include "reconfig.h"

namespace tesseract {

Reconfig::Reconfig(const std::string &name, int ni, int x_scale, int y_scale)

    : Network(NT_RECONFIG, name, ni, ni * x_scale * y_scale)

    , x_scale_(x_scale)

    , y_scale_(y_scale) {}

// Returns the shape output from the network given an input shape (which may

// be partially unknown ie zero).

StaticShape Reconfig::OutputShape(const StaticShape &input_shape) const {

  StaticShape result = input_shape;

  result.set_height(result.height() / y_scale_);

  result.set_width(result.width() / x_scale_);

  if (type_ != NT_MAXPOOL) {

    result.set_depth(result.depth() * y_scale_ * x_scale_);

  }

  return result;

}

// Returns an integer reduction factor that the network applies to the

// time sequence. Assumes that any 2-d is already eliminated. Used for

// scaling bounding boxes of truth data.

// WARNING: if GlobalMinimax is used to vary the scale, this will return

// the last used scale factor. Call it before any forward, and it will return

// the minimum scale factor of the paths through the GlobalMinimax.

int Reconfig::XScaleFactor() const {

  return x_scale_;

}

// Writes to the given file. Returns false in case of error.

bool Reconfig::Serialize(TFile *fp) const {

  return Network::Serialize(fp) && fp->Serialize(&x_scale_) && fp->Serialize(&y_scale_);

}

// Reads from the given file. Returns false in case of error.

bool Reconfig::DeSerialize(TFile *fp) {

  if (!fp->DeSerialize(&x_scale_)) {

    return false;

  }

  if (!fp->DeSerialize(&y_scale_)) {

    return false;

  }

  no_ = ni_ * x_scale_ * y_scale_;

  return true;

}

// Runs forward propagation of activations on the input line.

// See NetworkCpp for a detailed discussion of the arguments.

void Reconfig::Forward(bool debug, const NetworkIO &input, const TransposedArray *input_transpose,

                       NetworkScratch *scratch, NetworkIO *output) {

  output->ResizeScaled(input, x_scale_, y_scale_, no_);

  back_map_ = input.stride_map();

  StrideMap::Index dest_index(output->stride_map());

  do {

    int out_t = dest_index.t();

    StrideMap::Index src_index(input.stride_map(), dest_index.index(FD_BATCH),

                               dest_index.index(FD_HEIGHT) * y_scale_,

                               dest_index.index(FD_WIDTH) * x_scale_);

    // Stack x_scale_ groups of y_scale_ inputs together.

    for (int x = 0; x < x_scale_; ++x) {

      for (int y = 0; y < y_scale_; ++y) {

        StrideMap::Index src_xy(src_index);

        if (src_xy.AddOffset(x, FD_WIDTH) && src_xy.AddOffset(y, FD_HEIGHT)) {

          output->CopyTimeStepGeneral(out_t, (x * y_scale_ + y) * ni_, ni_, input, src_xy.t(), 0);

        }

      }

    }

  } while (dest_index.Increment());

}

// Runs backward propagation of errors on the deltas line.

// See NetworkCpp for a detailed discussion of the arguments.

bool Reconfig::Backward(bool debug, const NetworkIO &fwd_deltas, NetworkScratch *scratch,

                        NetworkIO *back_deltas) {

  back_deltas->ResizeToMap(fwd_deltas.int_mode(), back_map_, ni_);

  StrideMap::Index src_index(fwd_deltas.stride_map());

  do {

    int in_t = src_index.t();

    StrideMap::Index dest_index(back_deltas->stride_map(), src_index.index(FD_BATCH),

                                src_index.index(FD_HEIGHT) * y_scale_,

                                src_index.index(FD_WIDTH) * x_scale_);

    // Unstack x_scale_ groups of y_scale_ inputs that are together.

    for (int x = 0; x < x_scale_; ++x) {

      for (int y = 0; y < y_scale_; ++y) {

        StrideMap::Index dest_xy(dest_index);

        if (dest_xy.AddOffset(x, FD_WIDTH) && dest_xy.AddOffset(y, FD_HEIGHT)) {

          back_deltas->CopyTimeStepGeneral(dest_xy.t(), 0, ni_, fwd_deltas, in_t,

                                           (x * y_scale_ + y) * ni_);

        }

      }

    }

  } while (src_index.Increment());

  return needs_to_backprop_;

}

} // namespace tesseract.