BCECriterion was incorrect.

Fixed:
* forward/backward: inverted sign to produce neg ll (not pos)
* averaging over all elements in target, to properly support batches
* added epsilon to protect against 0s (divs and logs)

1 files changed, 50 insertions, 39 deletions

diff --git a/BCECriterion.lua b/BCECriterion.lua
index be9082e..8e366c8 100644
--- a/BCECriterion.lua
+++ b/BCECriterion.lua
@@ -1,56 +1,67 @@
 local BCECriterion, parent = torch.class('nn.BCECriterion', 'nn.Criterion')
 
+local eps = 1e-12
+
 function BCECriterion:__init()
    parent.__init(self)
    self.sizeAverage = true
 end
 
 function BCECriterion:updateOutput(input, target)
-    -- log(input) * target + log(1 - input) * (1 - target)
+   -- log(input) * target + log(1 - input) * (1 - target)
+
+   self.term1 = self.term1 or input.new()
+   self.term2 = self.term2 or input.new()
+   self.term3 = self.term3 or input.new()
 
-    self.term1 = self.term1 or input.new()
-    self.term2 = self.term2 or input.new()
-    self.term3 = self.term3 or input.new()
+   self.term1:resizeAs(input)
+   self.term2:resizeAs(input)
+   self.term3:resizeAs(input)
 
-    self.term1:resizeAs(input)
-    self.term2:resizeAs(input)
-    self.term3:resizeAs(input)
+   self.term1:fill(1):add(-1,target)
+   self.term2:fill(1):add(-1,input):add(eps):log():cmul(self.term1)
 
-    self.term1:fill(1):add(-1,target)
-    self.term2:fill(1):add(-1,input):log():cmul(self.term1)
-    
-    self.term3:copy(input):log():cmul(target)
-    self.term3:add(self.term2)
+   self.term3:copy(input):add(eps):log():cmul(target)
+   self.term3:add(self.term2)
 
-    if self.sizeAverage then
-    	self.term3:div(target:size(1))
-    end
+   if self.sizeAverage then
+      self.term3:div(target:nElement())
+   end
 
-    return self.term3:sum()
+   self.output = - self.term3:sum()
+
+   return self.output
 end
 
 function BCECriterion:updateGradInput(input, target)
-    -- target / input - (1 - target) / (1 - input)
-    
-    self.term1 = self.term1 or input.new()
-    self.term2 = self.term2 or input.new()
-    
-    self.term1:resizeAs(input)
-    self.term2:resizeAs(input)
-    
-    self.term1:fill(1):add(-1,target)
-    self.term2:fill(1):add(-1,input)
-
-    self.term1:cdiv(self.term2)
-
-    self.gradInput:resizeAs(input)
-    self.gradInput:copy(target):cdiv(input)
-
-    self.gradInput:add(-1,self.term1)
-
-    if self.sizeAverage then
-    	self.gradInput:div(target:size(1))
-    end
-    
-    return self.gradInput
+   -- target / input - (1 - target) / (1 - input)
+
+   self.term1 = self.term1 or input.new()
+   self.term2 = self.term2 or input.new()
+   self.term3 = self.term3 or input.new()
+
+   self.term1:resizeAs(input)
+   self.term2:resizeAs(input)
+   self.term3:resizeAs(input)
+
+   self.term1:fill(1):add(-1,target)
+   self.term2:fill(1):add(-1,input)
+
+   self.term2:add(eps)
+   self.term1:cdiv(self.term2)
+
+   self.term3:copy(input):add(eps)
+
+   self.gradInput:resizeAs(input)
+   self.gradInput:copy(target):cdiv(self.term3)
+
+   self.gradInput:add(-1,self.term1)
+
+   if self.sizeAverage then
+      self.gradInput:div(target:nElement())
+   end
+
+   self.gradInput:mul(-1)
+
+   return self.gradInput
 end