1 files changed, 33 insertions, 0 deletions
diff --git a/PairwiseDistance.lua b/PairwiseDistance.lua
new file mode 100644
index 0000000..638c58f
--- /dev/null
+++ b/PairwiseDistance.lua
@@ -0,0 +1,33 @@
+local PairwiseDistance, parent = torch.class('nn.PairwiseDistance', 'nn.Module')
+
+function PairwiseDistance:__init(p)
+   parent.__init(self)
+
+   -- state
+   self.gradInput = {torch.Tensor(), torch.Tensor()}
+   self.output = torch.Tensor(1)
+   self.norm=p
+end 
+  
+function PairwiseDistance:updateOutput(input)
+   self.output[1]=input[1]:dist(input[2],self.norm);
+   return self.output
+end
+
+local function mathsign(x) 
+   if x==0 then return  2*torch.random(2)-3; end
+   if x>0 then return 1; else return -1; end
+end
+
+function PairwiseDistance:updateGradInput(input, gradOutput)
+  self.gradInput[1]:resizeAs(input[1]) 
+  self.gradInput[2]:resizeAs(input[2]) 
+  self.gradInput[1]:copy(input[1])
+  self.gradInput[1]:add(-1, input[2])
+  if self.norm==1 then
+     self.gradInput[1]:apply(mathsign)
+  end
+  self.gradInput[1]:mul(gradOutput[1]);
+  self.gradInput[2]:zero():add(-1, self.gradInput[1])
+  return self.gradInput
+end