main_model.m

Standard model object recognition matlab code

function resp = main_model (stim,f_all,s_all,o_all,varargin)

% FUNCTION resp = main_model (stim,f_all,s_all,o_all,varargin)
%
% This function computes and returns all the activities of the
% units in the model for a given stimulus.  The activities of the
% units are determined by the stimulus and the connectivity
% (f_all), the mixing of scales (s_all), and operation (o_all),
% along with the responses from the previous layers.
%
% varargin is used to specify from which layer to start
% processing.  In other words, we can compute the response of
% higher layers based on some saved response of an earlier layer.
%
% Note we designate different layers in the order of
%  [S1 C1 S2b C2b S2 C2 S3 C3 VTU],
% Therefore, we need to make sure to branch into main route or
% bypass route appropropriately.

global all_quanta;
resp       = [];
prev_layer = stim;

if length(varargin) > 0
  start_layer = varargin{1};
else
  start_layer = 1;
end
end_layer = length(fieldnames(f_all));

if start_layer>1 & ~isstruct(prev_layer)
  error('Input to the model is not quite right.');
end

for curr_layer = start_layer:end_layer
  
  % Display the progress.
  %fprintf(['\b' num2str(curr_layer)]);
  
  f_str = ['f' num2str(curr_layer)];
  % Use the broken up filters.  See main_model_load_save.m
  %load(['Filt_f' num2str(curr_layer)]);
  %load(['Filt_s' num2str(curr_layer)]);
  %f = f_alone;
  %s = s_alone;
  %m = m_alone;
  
  if ~isstruct(getfield(f_all,f_str))
    error('Filter is not defined.');
  end
  
  o = o_all(curr_layer,:);
  % Branch into main routes, when bypass computation is also
  % present, because prev_layer for the main route is C1
  % response, not the response from C2b.  
  %
  % Cases when level = [1 1 1 1 1 ...] or [0 0 1 1 1 ...].
  % It should be okay when level = [0 0 0 0 1 ...]
  if (curr_layer==5) % Branch point
    if (start_layer==5) | (start_layer==3)
      % Case [0 0 1 1 1 ...] or 
      % Case [0 0 0 0 1 ...]
      prev_layer = stim; % stim must be resp from layer 2.
    else     
      % Case [1 1 1 1 1 ...] or
      % Case [1 1 0 0 1 ...]
      prev_layer = getfield(resp, 'r2');
    end
  end
  
  % Rescale the response, using sigmoid.  Note that we rescale
  % prev_layer, not next_layer.  This allows the saving of the
  % responses before the sigmoid transfer function, and makes it
  % easy to adjust the sigmoid parameters.  Note that
  % init_sigmoid_def is called to obtain the parameters from the
  % previous layer.
  [sigmoid_a, sigmoid_b] = init_sigmoid_def(curr_layer-1);
  if sigmoid_a > 0
    for ss = 1:length(fieldnames(prev_layer));
      p_tmp = getfield(prev_layer, ['s' num2str(ss)]);
      p_tmp = 1./(1+exp(-sigmoid_a.*(p_tmp-sigmoid_b))); 
      prev_layer = setfield(prev_layer,['s' num2str(ss)],p_tmp);
    end
  end

  % Get next layer in the model
  next_layer = comp_get_next_layer(prev_layer, ...
      getfield(f_all,f_str), o);

  % Mixing scales.
  m = getfield (s_all, ['m' num2str(curr_layer)]);
  if max(m) > 0 
    next_layer = comp_mix_scales(next_layer, ...
	m, getfield(s_all,f_str),o);  
  end

  % Quantize responses.
  num_quanta = all_quanta(curr_layer);
  next_layer = aux_quantize_resp(next_layer,num_quanta);
  
  prev_layer = next_layer;

  % Save the response.
  resp = setfield(resp,['r' num2str(curr_layer)],next_layer);
end