Dropout

2 files changed, 42 insertions, 0 deletions

diff --git a/Dropout.lua b/Dropout.lua
new file mode 100644
index 0000000..ac6c463
--- /dev/null
+++ b/Dropout.lua
@@ -0,0 +1,41 @@
+local Dropout, Parent = torch.class('nn.Dropout', 'nn.Module')
+
+function Dropout:__init(p)
+   Parent.__init(self)
+   self.p = p or 0.5
+   self.train = true
+   if self.p >= 1 or self.p < 0 then
+      error('<Dropout> illegal percentage, must be 0 <= p < 1')
+   end
+   self.noise = torch.Tensor()
+   self.fnoise = torch.Tensor()
+end
+
+function Dropout:updateOutput(input)
+   self.output:resizeAs(input):copy(input)
+   if self.train then
+      self.fnoise = self.fnoise:float()
+      self.fnoise:resize(input:size())
+      self.noise:resizeAs(input)
+      self.fnoise:bernoulli(1-self.p)
+      self.noise:copy(self.fnoise)
+      self.output:cmul(self.noise)
+   else
+      self.output:mul(1-self.p)
+   end
+   return self.output
+end
+
+function Dropout:updateGradInput(input, gradOutput)
+   if self.train then
+      self.gradInput:resizeAs(gradOutput):copy(gradOutput)
+      self.gradInput:cmul(self.noise) -- simply mask the gradients with the noise vector
+   else
+      error('backprop only defined while training')
+   end
+   return self.gradInput
+end
+
+function Dropout:setp(p)
+   self.p = p
+end
diff --git a/init.lua b/init.lua
index 757c9ec..59275ef 100644
--- a/init.lua
+++ b/init.lua
@@ -26,6 +26,7 @@ include('Mul.lua')
 include('MulConstant.lua')
 include('Add.lua')
 include('AddConstant.lua')
+include('Dropout.lua')
 
 include('CAddTable.lua')
 include('CDivTable.lua')