word_and_vision_regions_conf_train.m

function [net, stats] = word_and_vision_regions_conf_train_wkshp(net, imdb, getBatch, varargin)
%CNN_TRAIN  An example implementation of SGD for training CNNs
%    CNN_TRAIN() is an example learner implementing stochastic
%    gradient descent with momentum to train a CNN. It can be used
%    with different datasets and tasks by providing a suitable
%    getBatch function.
%
%    The function automatically restarts after each training epoch by
%    checkpointing.
%
%    The function supports training on CPU or on one or more GPUs
%    (specify the list of GPU IDs in the `gpus` option).

% Copyright (C) 2014-16 Andrea Vedaldi.
% All rights reserved.
%
% This file is part of the VLFeat library and is made available under
% the terms of the BSD license (see the COPYING file).

opts.expDir = fullfile('data','exp') ;
opts.continue = true ;
opts.batchSize = 256 ;
opts.numSubBatches = 1 ;
opts.train = [] ;
opts.val = [] ;
opts.gpus = [] ;
opts.prefetch = false ;
opts.numEpochs = 300 ;
opts.learningRate = 0.001 ;
opts.weightDecay = 0.0005 ;
opts.momentum = 0.9 ;
opts.randomSeed = 0 ;
opts.memoryMapFile = fullfile(tempdir, 'matconvnet.bin') ;
opts.profile = false ;

opts.conserveMemory = true ;
opts.backPropDepth = +inf ;
opts.sync = false ;
opts.cudnn = true ;
opts.errorFunction = 'multiclass' ;
opts.errorLabels = {} ;
opts.plotDiagnostics = false ;
opts.plotStatistics = true;
opts = vl_argparse(opts, varargin) ;

if ~exist(opts.expDir, 'dir'), mkdir(opts.expDir) ; end
if isempty(opts.train), opts.train = find(imdb.images.set==1) ; end
if isempty(opts.val), opts.val = find(imdb.images.set==2) ; end
if isnan(opts.train), opts.train = [] ; end
if isnan(opts.val), opts.val = [] ; end

% -------------------------------------------------------------------------
%                                                            Initialization
% -------------------------------------------------------------------------

net = vl_simplenn_tidy(net); % fill in some eventually missing values
net.layers{end-1}.precious = 1; % do not remove predictions, used for error
vl_simplenn_display(net, 'batchSize', opts.batchSize) ;

evaluateMode = isempty(opts.train) ;
if ~evaluateMode
  for i=1:numel(net.layers)
    if isfield(net.layers{i}, 'weights')
      J = numel(net.layers{i}.weights) ;
      if ~isfield(net.layers{i}, 'learningRate')
        net.layers{i}.learningRate = ones(1, J, 'single') ;
      end
      if ~isfield(net.layers{i}, 'weightDecay')
        net.layers{i}.weightDecay = ones(1, J, 'single') ;
      end
    end
  end
end

% setup error calculation function
hasError = true ;
if isstr(opts.errorFunction)
  switch opts.errorFunction
    case 'none'
      opts.errorFunction = @error_none ;
      hasError = false ;
    case 'multiclass'
      opts.errorFunction = @error_multiclass ;
      if isempty(opts.errorLabels), opts.errorLabels = {'top1err', 'top5err'} ; end
    case 'binary'
      opts.errorFunction = @error_binary ;
      if isempty(opts.errorLabels), opts.errorLabels = {'binerr'} ; end
    otherwise
      error('Unknown error function ''%s''.', opts.errorFunction) ;
  end
end

state.getBatch = getBatch ;
stats = [] ;

% -------------------------------------------------------------------------
%                                                        Train and validate
% -------------------------------------------------------------------------

modelPath = @(ep) fullfile(opts.expDir, sprintf('net-epoch-%d.mat', ep));
modelFigPath = fullfile(opts.expDir, 'net-train.pdf') ;

start = opts.continue * findLastCheckpoint(opts.expDir) ;
if start >= 1
  fprintf('%s: resuming by loading epoch %d\n', mfilename, start) ;
  [net, stats] = loadState(modelPath(start)) ;
end

for epoch=start+1:opts.numEpochs

  % Set the random seed based on the epoch and opts.randomSeed.
  % This is important for reproducibility, including when training
  % is restarted from a checkpoint.

  rng(epoch + opts.randomSeed) ;
  prepareGPUs(opts, epoch == start+1) ;

  % Train for one epoch.

  state.epoch = epoch ;
  state.learningRate = opts.learningRate(min(epoch, numel(opts.learningRate))) ;
  state.train = opts.train(randperm(numel(opts.train))) ; % shuffle
  state.val = opts.val(randperm(numel(opts.val))) ;
  state.imdb = imdb ;

  if numel(opts.gpus) <= 1
    [net,stats.train(epoch),prof] = process_epoch(net, state, opts, 'train') ;
    [~,stats.val(epoch)] = process_epoch(net, state, opts, 'val') ;
    if opts.profile
      profview(0,prof) ;
      keyboard ;
    end
  else
    spmd(numGpus)
      [net_, stats_.train, prof_] = process_epoch(net, state, opts, 'train') ;
      [~, stats_.val] = process_epoch(net_, state, opts, 'val') ;
      if labindex == 1, savedNet_ = net_ ; end
    end
    net = savedNet_{1} ;
    stats__ = accumulateStats(stats_) ;
    stats.train(epoch) = stats__.train ;
    stats.val(epoch) = stats__.val ;
    if opts.profile
      mpiprofile('viewer', [prof_{:,1}]) ;
      keyboard ;
    end
    clear net_ stats_ stats__ savedNet_ ;
  end

  % save
  if ~evaluateMode
    saveState(modelPath(epoch), net, stats) ;
  end

  if opts.plotStatistics
    switchFigure(1) ; clf ;
    plots = setdiff(...
      cat(2,...
      fieldnames(stats.train)', ...
      fieldnames(stats.val)'), {'num', 'time'}) ;
    for p = plots
      p = char(p) ;
      values = zeros(0, epoch) ;
      leg = {} ;
      for f = {'train', 'val'}
        f = char(f) ;
        if isfield(stats.(f), p)
          tmp = [stats.(f).(p)] ;
          values(end+1,:) = tmp(1,:)' ;
          leg{end+1} = f ;
        end
      end
      subplot(1,numel(plots),find(strcmp(p,plots))) ;
      plot(1:epoch, values','o-') ;
      xlabel('epoch') ;
      title(p) ;
      legend(leg{:}) ;
      grid on ;
    end
    drawnow ;
    print(1, modelFigPath, '-dpdf') ;
  end
end

% -------------------------------------------------------------------------
function err = error_multiclass(opts, labels, res)
% -------------------------------------------------------------------------
predictions = gather(res(end-1).x) ;
[~,predictions] = sort(predictions, 3, 'descend') ;

% be resilient to badly formatted labels
if numel(labels) == size(predictions, 4)
  labels = reshape(labels,1,1,1,[]) ;
end

% skip null labels
mass = single(labels(:,:,1,:) > 0) ;
if size(labels,3) == 2
  % if there is a second channel in labels, used it as weights
  mass = mass .* labels(:,:,2,:) ;
  labels(:,:,2,:) = [] ;
end

m = min(5, size(predictions,3)) ;

error = ~bsxfun(@eq, predictions, labels) ;
err(1,1) = sum(sum(sum(mass .* error(:,:,1,:)))) ;
err(2,1) = sum(sum(sum(mass .* min(error(:,:,1:m,:),[],3)))) ;

% -------------------------------------------------------------------------
function err = error_binary(opts, labels, res)
% -------------------------------------------------------------------------
predictions = gather(res(end-1).x) ;
error = bsxfun(@times, predictions, labels) < 0 ;
err = sum(error(:)) ;

% -------------------------------------------------------------------------
function err = error_none(opts, labels, res)
% -------------------------------------------------------------------------
err = zeros(0,1) ;

% -------------------------------------------------------------------------
function  [net_cpu,stats,prof] = process_epoch(net, state, opts, mode)
% -------------------------------------------------------------------------

% initialize empty momentum
if strcmp(mode,'train')
  state.momentum = {} ;
  for i = 1:numel(net.layers)
    if isfield(net.layers{i}, 'weights')
      for j = 1:numel(net.layers{i}.weights)
        state.layers{i}.momentum{j} = 0 ;
      end
    end
  end
end

% move CNN  to GPU as needed
numGpus = numel(opts.gpus) ;
if numGpus >= 1
    %  net = vl_simplenn_move(net, 'gpu') ;
    net = vl_simplenn_move2(net, 'gpu') ;
end
if numGpus > 1
  mmap = map_gradients(opts.memoryMapFile, net, numGpus) ;
else
  mmap = [] ;
end

% profile
if opts.profile
  if numGpus <= 1
    profile clear ;
    profile on ;
  else
    mpiprofile reset ;
    mpiprofile on ;
  end
end

subset = state.(mode) ;
num = 0 ;
stats.num = 0 ; % return something even if subset = []
stats.time = 0 ;
adjustTime = 0 ;
res = [] ;
error = [] ;

start = tic ;
for t=1:opts.batchSize:numel(subset)
  fprintf('%s: epoch %02d: %3d/%3d:', mode, state.epoch, ...
          fix((t-1)/opts.batchSize)+1, ceil(numel(subset)/opts.batchSize)) ;
  batchSize = min(opts.batchSize, numel(subset) - t + 1) ;

  for s=1:opts.numSubBatches
    % get this image batch and prefetch the next
    batchStart = t + (labindex-1) + (s-1) * numlabs ;
    batchEnd = min(t+opts.batchSize-1, numel(subset)) ;
    batch = subset(batchStart : opts.numSubBatches * numlabs : batchEnd) ;
    num = num + numel(batch) ;
    if numel(batch) == 0, continue ; end

    %    [im, labels] = state.getBatch(state.imdb, batch) ;
    [im, labels, annotator_choice_frac, region_feats] = state.getBatch(state.imdb, batch) ;
    if opts.prefetch
      if s == opts.numSubBatches
        batchStart = t + (labindex-1) + opts.batchSize ;
        batchEnd = min(t+2*opts.batchSize-1, numel(subset)) ;
      else
        batchStart = batchStart + numlabs ;
      end
      nextBatch = subset(batchStart : opts.numSubBatches * numlabs : batchEnd) ;
      state.getBatch(state.imdb, nextBatch) ;
    end

    if numGpus >= 1
      im = gpuArray(im) ;
    end

    if strcmp(mode, 'train')
      dzdy = 1 ;
      evalMode = 'normal' ;
    else
      dzdy = [] ;
      evalMode = 'test' ;
    end
    
    net.layers{end}.correct_answer = labels;
    net.layers{end}.annotator_choice_frac = annotator_choice_frac;
    net.layers{end-7}.region_feats = gpuArray(region_feats);
    res = vl_simplenn(net, im, dzdy, res, ...
                      'accumulate', s ~= 1, ...
                      'mode', evalMode, ...
                      'conserveMemory', opts.conserveMemory, ...
                      'backPropDepth', opts.backPropDepth, ...
                      'sync', opts.sync, ...
                      'cudnn', opts.cudnn) ;
    % accumulate errors
    error= sum([error,gather(res(end).x)]);

  end

  % accumulate gradient
  if strcmp(mode, 'train')
    if ~isempty(mmap)
      write_gradients(mmap, net) ;
      labBarrier() ;
    end
    [state, net] = accumulate_gradients(state, net, res, opts, batchSize, mmap) ;
  end

  % get statistics
  time = toc(start) + adjustTime ;
  batchTime = time - stats.time ;
  
  stats = [];%extractStats(net, opts, error / num) ;
  stats.num = num ;
  stats.time = time ;
  currentSpeed = batchSize / batchTime ;
  averageSpeed = (t + batchSize - 1) / time ;
  if t == opts.batchSize + 1
    % compensate for the first iteration, which is an outlier
    adjustTime = 2*batchTime - time ;
    stats.time = time + adjustTime ;
  end

  fprintf(' %.1f (%.1f) Hz', averageSpeed, currentSpeed) ;
  for f = setdiff(fieldnames(stats)', {'num', 'time'})
    f = char(f) ;
    fprintf(' %s:', f) ;
    fprintf(' %.3f', stats.(f)) ;
  end
  n = (t + batchSize - 1) / max(1,numlabs) ;
  fprintf(' obj:%.3g', error/n) ;
  fprintf(' batch obj:%.3g', res(end).x/batchSize) ;
  fprintf('\n') ;
  % collect diagnostic statistics
  if strcmp(mode, 'train') && opts.plotDiagnostics
    switchfigure(2) ; clf ;
    diagn = [res.stats] ;
    diagnvar = horzcat(diagn.variation) ;
    barh(diagnvar) ;
    set(gca,'TickLabelInterpreter', 'none', ...
      'YTick', 1:numel(diagnvar), ...
      'YTickLabel',horzcat(diagn.label), ...
      'YDir', 'reverse', ...
      'XScale', 'log', ...
      'XLim', [1e-5 1]) ;
    drawnow ;
  end
end

if ~isempty(mmap)
  unmap_gradients(mmap) ;
end

if opts.profile
  if numGpus <= 1
    prof = profile('info') ;
    profile off ;
  else
    prof = mpiprofile('info');
    mpiprofile off ;
  end
else
  prof = [] ;
end

net_cpu = vl_simplenn_move(net, 'cpu') ;

% -------------------------------------------------------------------------
function [state, net] = accumulate_gradients(state, net, res, opts, batchSize, mmap)
% -------------------------------------------------------------------------
numGpus = numel(opts.gpus) ;
otherGpus = setdiff(1:numGpus, labindex) ;

for l=numel(net.layers):-1:1
  for j=1:numel(res(l).dzdw)

    % accumualte gradients from multiple labs (GPUs) if needed
    if numGpus > 1
      tag = sprintf('l%d_%d',l,j) ;
      for g = otherGpus
        tmp = gpuArray(mmap.Data(g).(tag)) ;
        res(l).dzdw{j} = res(l).dzdw{j} + tmp ;
      end
    end

    if j == 3 && strcmp(net.layers{l}.type, 'bnorm')
      % special case for learning bnorm moments
      thisLR = net.layers{l}.learningRate(j) ;
      net.layers{l}.weights{j} = ...
        (1 - thisLR) * net.layers{l}.weights{j} + ...
        (thisLR/batchSize) * res(l).dzdw{j} ;
    else
      % standard gradient training
      thisDecay = opts.weightDecay * net.layers{l}.weightDecay(j) ;
      thisLR = state.learningRate * net.layers{l}.learningRate(j) ;
      state.layers{l}.momentum{j} = opts.momentum * state.layers{l}.momentum{j} ...
        - thisDecay * net.layers{l}.weights{j} ...
        - (1 / batchSize) * res(l).dzdw{j} ;
      net.layers{l}.weights{j} = net.layers{l}.weights{j} + ...
        thisLR * state.layers{l}.momentum{j} ;
    end

    % if requested, collect some useful stats for debugging
    if opts.plotDiagnostics
      variation = [] ;
      label = '' ;
      switch net.layers{l}.type
        case {'conv','convt'}
          variation = thisLR * mean(abs(state.layers{l}.momentum{j}(:))) ;
          if j == 1 % fiters
            base = mean(abs(net.layers{l}.weights{j}(:))) ;
            label = 'filters' ;
          else % biases
            base = mean(abs(res(l+1).x(:))) ;
            label = 'biases' ;
          end
          variation = variation / base ;
          label = sprintf('%s_%s', net.layers{l}.name, label) ;
      end
      res(l).stats.variation(j) = variation ;
      res(l).stats.label{j} = label ;
    end
  end
end

% -------------------------------------------------------------------------
function mmap = map_gradients(fname, net, numGpus)
% -------------------------------------------------------------------------
format = {} ;
for i=1:numel(net.layers)
  for j=1:numel(net.layers(i).params)
    par = net.layers(i).params{j} ;
    format(end+1,1:3) = {'single', size(par), sprintf('l%d_%d',i,j)} ;
  end
end
format(end+1,1:3) = {'double', [3 1], 'errors'} ;
if ~exist(fname) && (labindex == 1)
  f = fopen(fname,'wb') ;
  for g=1:numGpus
    for i=1:size(format,1)
      fwrite(f,zeros(format{i,2},format{i,1}),format{i,1}) ;
    end
  end
  fclose(f) ;
end
labBarrier() ;
mmap = memmapfile(fname, ...
                  'Format', format, ...
                  'Repeat', numGpus, ...
                  'Writable', true) ;

% -------------------------------------------------------------------------
function write_gradients(mmap, net, res)
% -------------------------------------------------------------------------
for i=1:numel(net.layers)
  for j=1:numel(res(i).dzdw)
    mmap.Data(labindex).(sprintf('l%d_%d',i,j)) = gather(res(i).dzdw{j}) ;
  end
end

% -------------------------------------------------------------------------
function unmap_gradients(mmap)
% -------------------------------------------------------------------------

% -------------------------------------------------------------------------
function stats = accumulateStats(stats_)
% -------------------------------------------------------------------------

for s = {'train', 'val'}
  s = char(s) ;
  total = 0 ;

  % initialize stats stucture with same fields and same order as
  % stats_{1}
  stats__ = stats_{1} ;
  names = fieldnames(stats__.(s))' ;
  values = zeros(1, numel(names)) ;
  fields = cat(1, names, num2cell(values)) ;
  stats.(s) = struct(fields{:}) ;

  for g = 1:numel(stats_)
    stats__ = stats_{g} ;
    num__ = stats__.(s).num ;
    total = total + num__ ;

    for f = setdiff(fieldnames(stats__.(s))', 'num')
      f = char(f) ;
      stats.(s).(f) = stats.(s).(f) + stats__.(s).(f) * num__ ;

      if g == numel(stats_)
        stats.(s).(f) = stats.(s).(f) / total ;
      end
    end
  end
  stats.(s).num = total ;
end

% -------------------------------------------------------------------------
function stats = extractStats(net, opts, errors)
% -------------------------------------------------------------------------
stats.objective = errors(1) ;
for i = 1:numel(opts.errorLabels)
  stats.(opts.errorLabels{i}) = errors(i+1) ;
end

% -------------------------------------------------------------------------
function saveState(fileName, net, stats)
% -------------------------------------------------------------------------
save(fileName, 'net', 'stats') ;

% -------------------------------------------------------------------------
function [net, stats] = loadState(fileName)
% -------------------------------------------------------------------------
load(fileName, 'net', 'stats') ;
net = vl_simplenn_tidy(net) ;

% -------------------------------------------------------------------------
function epoch = findLastCheckpoint(modelDir)
% -------------------------------------------------------------------------
list = dir(fullfile(modelDir, 'net-epoch-*.mat')) ;
tokens = regexp({list.name}, 'net-epoch-([\d]+).mat', 'tokens') ;
epoch = cellfun(@(x) sscanf(x{1}{1}, '%d'), tokens) ;
epoch = max([epoch 0]) ;

% -------------------------------------------------------------------------
function switchFigure(n)
% -------------------------------------------------------------------------
if get(0,'CurrentFigure') ~= n
  try
    set(0,'CurrentFigure',n) ;
  catch
    figure(n) ;
  end
end

% -------------------------------------------------------------------------
function prepareGPUs(opts, cold)
% -------------------------------------------------------------------------
numGpus = numel(opts.gpus) ;
if numGpus > 1
  % check parallel pool integrity as it could have timed out
  pool = gcp('nocreate') ;
  if ~isempty(pool) && pool.NumWorkers ~= numGpus
    delete(pool) ;
  end
  pool = gcp('nocreate') ;
  if isempty(pool)
    parpool('local', numGpus) ;
    cold = true ;
  end
  if exist(opts.memoryMapFile)
    delete(opts.memoryMapFile) ;
  end
end
if numGpus >= 1 && cold
  fprintf('%s: resetting GPU\n', mfilename)
  if numGpus == 1
      %    gpuDevice(opts.gpus)
  else
    spmd, gpuDevice(opts.gpus(labindex)), end
  end
end