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lib/AI/NNFlex/Backprop.pm  view on Meta::CPAN

##########################################################
# AI::NNFlex::Backprop
##########################################################
# Backprop with simple (non adaptive) momentum
##########################################################
# Versions
# ========
#
# 1.0	20050121	CColbourn	New module
# 1.1	20050201	CColbourn	Added call to activation
#					function slope instead
#					of hardcoded 1-y*y
#
# 1.2	20050218	CColbourn	Mod'd to change weight
#					indexing to array for
#					nnflex 0.16
#
# 1.3	20050307	CColbourn	packaged as a subclass of NNFLex
#
# 1.4	20050313	CColbourn	modified the slope function call
#					to avoid using eval
#
# 1.5	20050314	CColbourn	applied fahlman constant
# 					Renamed Backprop.pm, see CHANGES
#
##########################################################
# ToDo
# ----
#
#
###########################################################
#

package AI::NNFlex::Backprop;
use AI::NNFlex;
use AI::NNFlex::Feedforward;
use base qw(AI::NNFlex::Feedforward AI::NNFlex);
use strict;


sub calc_error
{
	my $network = shift;

	my $outputPatternRef = shift;
	my @outputPattern = @$outputPatternRef;

	my @debug = @{$network->{'debug'}};

	if (scalar @debug > 0)
	{$network->dbug ("Output pattern @outputPattern received by Backprop",4);}


	my $outputLayer = $network->{'layers'}->[-1]->{'nodes'};

	if (scalar @$outputLayer != scalar @outputPattern)
	{	
		$network->dbug ("Wrong number of output values, net has ".scalar @$outputLayer." nodes",0);
		return 0;
	}

	# Now calculate the error
	my $counter=0;
	foreach (@$outputLayer)
	{	
		my $value = $_->{'activation'} - $outputPattern[$counter];


		if ($_->{'errorfunction'})
		{
			my $errorfunction = $_->{'errorfunction'};
			$value = $network->$errorfunction($value);
		}