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local SpatialDivisiveNormalization, parent = torch.class('nn.SpatialDivisiveNormalization','nn.Module')
function SpatialDivisiveNormalization:__init(nInputPlane, kernel, threshold, thresval)
parent.__init(self)
-- get args
self.nInputPlane = nInputPlane or 1
self.kernel = kernel or torch.Tensor(9,9):fill(1)
self.threshold = threshold or 1e-4
self.thresval = thresval or threshold or 1e-4
local kdim = self.kernel:nDimension()
-- check args
if kdim ~= 2 and kdim ~= 1 then
error('<SpatialDivisiveNormalization> averaging kernel must be 2D or 1D')
end
if (self.kernel:size(1) % 2) == 0 or (kdim == 2 and (self.kernel:size(2) % 2) == 0) then
error('<SpatialDivisiveNormalization> averaging kernel must have ODD dimensions')
end
-- padding values
local padH = math.floor(self.kernel:size(1)/2)
local padW = padH
if kdim == 2 then
padW = math.floor(self.kernel:size(2)/2)
end
-- create convolutional mean estimator
self.meanestimator = nn.Sequential()
self.meanestimator:add(nn.SpatialZeroPadding(padW, padW, padH, padH))
if kdim == 2 then
self.meanestimator:add(nn.SpatialConvolution(self.nInputPlane, 1, self.kernel:size(2), self.kernel:size(1)))
else
self.meanestimator:add(nn.SpatialConvolutionMap(nn.tables.oneToOne(self.nInputPlane), self.kernel:size(1), 1))
self.meanestimator:add(nn.SpatialConvolution(self.nInputPlane, 1, 1, self.kernel:size(1)))
end
self.meanestimator:add(nn.Replicate(self.nInputPlane))
-- create convolutional std estimator
self.stdestimator = nn.Sequential()
self.stdestimator:add(nn.Square())
self.stdestimator:add(nn.SpatialZeroPadding(padW, padW, padH, padH))
if kdim == 2 then
self.stdestimator:add(nn.SpatialConvolution(self.nInputPlane, 1, self.kernel:size(2), self.kernel:size(1)))
else
self.stdestimator:add(nn.SpatialConvolutionMap(nn.tables.oneToOne(self.nInputPlane), self.kernel:size(1), 1))
self.stdestimator:add(nn.SpatialConvolution(self.nInputPlane, 1, 1, self.kernel:size(1)))
end
self.stdestimator:add(nn.Replicate(self.nInputPlane))
self.stdestimator:add(nn.Sqrt())
-- set kernel and bias
if kdim == 2 then
self.kernel:div(self.kernel:sum() * self.nInputPlane)
for i = 1,self.nInputPlane do
self.meanestimator.modules[2].weight[1][i] = self.kernel
self.stdestimator.modules[3].weight[1][i] = self.kernel
end
self.meanestimator.modules[2].bias:zero()
self.stdestimator.modules[3].bias:zero()
else
self.kernel:div(self.kernel:sum() * math.sqrt(self.nInputPlane))
for i = 1,self.nInputPlane do
self.meanestimator.modules[2].weight[i]:copy(self.kernel)
self.meanestimator.modules[3].weight[1][i]:copy(self.kernel)
self.stdestimator.modules[3].weight[i]:copy(self.kernel)
self.stdestimator.modules[4].weight[1][i]:copy(self.kernel)
end
self.meanestimator.modules[2].bias:zero()
self.meanestimator.modules[3].bias:zero()
self.stdestimator.modules[3].bias:zero()
self.stdestimator.modules[4].bias:zero()
end
-- other operation
self.normalizer = nn.CDivTable()
self.divider = nn.CDivTable()
self.thresholder = nn.Threshold(self.threshold, self.thresval)
-- coefficient array, to adjust side effects
self.coef = torch.Tensor(1,1,1)
end
function SpatialDivisiveNormalization:updateOutput(input)
-- compute side coefficients
if (input:size(3) ~= self.coef:size(3)) or (input:size(2) ~= self.coef:size(2)) then
local ones = input.new():resizeAs(input):fill(1)
self.coef = self.meanestimator:updateOutput(ones)
self.coef = self.coef:clone()
end
-- normalize std dev
self.localstds = self.stdestimator:updateOutput(input)
self.adjustedstds = self.divider:updateOutput{self.localstds, self.coef}
self.thresholdedstds = self.thresholder:updateOutput(self.adjustedstds)
self.output = self.normalizer:updateOutput{input, self.thresholdedstds}
-- done
return self.output
end
function SpatialDivisiveNormalization:updateGradInput(input, gradOutput)
-- resize grad
self.gradInput:resizeAs(input):zero()
-- backprop through all modules
local gradnorm = self.normalizer:updateGradInput({input, self.thresholdedstds}, gradOutput)
local gradadj = self.thresholder:updateGradInput(self.adjustedstds, gradnorm[2])
local graddiv = self.divider:updateGradInput({self.localstds, self.coef}, gradadj)
self.gradInput:add(self.stdestimator:updateGradInput(input, graddiv[1]))
self.gradInput:add(gradnorm[1])
-- done
return self.gradInput
end
function SpatialDivisiveNormalization:type(type)
parent.type(self,type)
self.meanestimator:type(type)
self.stdestimator:type(type)
self.divider:type(type)
self.normalizer:type(type)
self.thresholder:type(type)
return self
end
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