text: #include "maxpool_layer.h"
  #include "cuda.h"
  #include <malloc.h>
  #include <stdio.h>
  #include <float.h>
  
  /*
  image get_maxpool_image(maxpool_layer l)
  {
      int h = l.out_h;
      int w = l.out_w;
      int c = l.c;
      return float_to_image(w,h,c,l.output);
  }
  
  image get_maxpool_delta(maxpool_layer l)
  {
      int h = l.out_h;
      int w = l.out_w;
      int c = l.c;
      return float_to_image(w,h,c,l.delta);
  }
  */
  
  maxpool_layer make_maxpool_layer(int batch, int h, int w, int c, int size, int stride)
  {
      fprintf(stderr, "Maxpool Layer: %d x %d x %d image, %d size, %d stride\n", h,w,c,size,stride);
      maxpool_layer l = {0};
      l.type = MAXPOOL;
      l.batch = batch;
      l.h = h;
      l.w = w;
      l.c = c;
      l.out_w = (w-1)/stride + 1;
      l.out_h = (h-1)/stride + 1;
      l.out_c = c;
      l.outputs = l.out_h * l.out_w * l.out_c;
      l.inputs = h*w*c;
      l.size = size;
      l.stride = stride;
      int output_size = l.out_h * l.out_w * l.out_c * batch;
      l.indexes = calloc(output_size, sizeof(int));
      l.output =  calloc(output_size, sizeof(float));
      l.delta =   calloc(output_size, sizeof(float));
      #ifdef WITH_CUDA
      l.indexes_gpu = cuda_make_int_array(output_size);
      l.output_gpu  = cuda_make_array(l.output, output_size);
      l.delta_gpu   = cuda_make_array(l.delta, output_size);
      #endif
      return l;
  }
  
  void resize_maxpool_layer(maxpool_layer *l, int w, int h)
  {
      int stride = l->stride;
      l->h = h;
      l->w = w;
      l->inputs = h*w*l->c;
  
      l->out_w = (w-1)/stride + 1;
      l->out_h = (h-1)/stride + 1;
      l->outputs = l->out_w * l->out_h * l->c;
      int output_size = l->outputs * l->batch;
  
      l->indexes = realloc(l->indexes, output_size * sizeof(int));
      l->output = realloc(l->output, output_size * sizeof(float));
      l->delta = realloc(l->delta, output_size * sizeof(float));
  
      #ifdef WITH_CUDA
      cuda_free((float *)l->indexes_gpu);
      cuda_free(l->output_gpu);
      cuda_free(l->delta_gpu);
      l->indexes_gpu = cuda_make_int_array(output_size);
      l->output_gpu  = cuda_make_array(l->output, output_size);
      l->delta_gpu   = cuda_make_array(l->delta,  output_size);
      #endif
  }
  
  void forward_maxpool_layer(const maxpool_layer l, network_state state)
  {
      int b,i,j,k,m,n;
      int w_offset = (-l.size-1)/2 + 1;
      int h_offset = (-l.size-1)/2 + 1;
  
      int h = (l.h-1)/l.stride + 1;
      int w = (l.w-1)/l.stride + 1;
      int c = l.c;
  
      for(b = 0; b < l.batch; ++b){
          for(k = 0; k < c; ++k){
              for(i = 0; i < h; ++i){
                  for(j = 0; j < w; ++j){
                      int out_index = j + w*(i + h*(k + c*b));
                      float max = -FLT_MAX;
                      int max_i = -1;
                      for(n = 0; n < l.size; ++n){
                          for(m = 0; m < l.size; ++m){
                              int cur_h = h_offset + i*l.stride + n;
                              int cur_w = w_offset + j*l.stride + m;
                              int index = cur_w + l.w*(cur_h + l.h*(k + b*l.c));
                              int valid = (cur_h >= 0 && cur_h < l.h &&
                                           cur_w >= 0 && cur_w < l.w);
                              float val = (valid != 0) ? state.input[index] : -FLT_MAX;
                              max_i = (val > max) ? index : max_i;
                              max   = (val > max) ? val   : max;
                          }
                      }
                      l.output[out_index] = max;
                      l.indexes[out_index] = max_i;
                  }
              }
          }
      }
  }
  
  void backward_maxpool_layer(const maxpool_layer l, network_state state)
  {
      int i;
      int h = (l.h-1)/l.stride + 1;
      int w = (l.w-1)/l.stride + 1;
      int c = l.c;
      for(i = 0; i < h*w*c*l.batch; ++i){
          int index = l.indexes[i];
          state.delta[index] += l.delta[i];
      }
  }
  
  