------------------------------------------------------------------------

--[[ Constant ]]--

-- Outputs a constant value given an input.

-- If nInputDim is specified, uses the input to determine the size of

-- the batch. The value is then replicated over the batch.

-- You can use this with nn.ConcatTable() to append constant inputs to

-- an input : nn.ConcatTable():add(nn.Constant(v)):add(nn.Identity()) .

------------------------------------------------------------------------

local Constant, parent = torch.class("nn.Constant", "nn.Module")

function Constant:__init(value, nInputDim)

self.value = value

if torch.type(self.value) == 'number' then

self.value = torch.Tensor{self.value}

end

assert(torch.isTensor(self.value), "Expecting number or tensor at arg 1")

self.nInputDim = nInputDim

parent.__init(self)

end

function Constant:updateOutput(input)

if self.nInputDim and input:dim() > self.nInputDim then

local vsize = self.value:size():totable()

self.output:resize(input:size(1), table.unpack(vsize))

local value = self.value:view(1, table.unpack(vsize))

self.output:copy(value:expand(self.output:size()))

else

self.output:resize(self.value:size()):copy(self.value)

end

return self.output

end

function Constant:updateGradInput(input, gradOutput)

self.gradInput:resizeAs(input):zero()

return self.gradInput

end