From a38407a57def785acc819066db70f1649da47f03 Mon Sep 17 00:00:00 2001
From: soumith <soumith@fb.com>
Date: Fri, 2 Jan 2015 20:42:12 -0800
Subject: speedup and optimizations for SparseLinear

---
 SparseLinear.lua | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

(limited to 'SparseLinear.lua')

diff --git a/SparseLinear.lua b/SparseLinear.lua
index 735d0ed..ca15be6 100644
--- a/SparseLinear.lua
+++ b/SparseLinear.lua
@@ -4,11 +4,16 @@ function SparseLinear:__init(inputSize, outputSize)
    parent.__init(self)
 
    self.weightDecay = 0
-   self.weight = torch.Tensor(outputSize, inputSize)
-   self.bias = torch.Tensor(outputSize)
-   self.gradWeight = torch.Tensor(outputSize, inputSize)
-   self.gradBias = torch.Tensor(outputSize)
-   self.lastInput = torch.Tensor()
+   self.weight = torch.Tensor(outputSize, inputSize):zero()
+   self.bias = torch.Tensor(outputSize):zero()
+   self.gradWeight = torch.Tensor(outputSize, inputSize):zero()
+   self.gradBias = torch.Tensor(outputSize):zero()
+   self.lastInput = nil
+
+   if torch.getnumthreads() > 1 and outputSize >= 128 then
+     self.shardBuffer = torch.Tensor(outputSize, torch.getnumthreads())
+   end
+
    -- state
    self.gradInput:resize(inputSize)
    self.output:resize(outputSize)
@@ -20,7 +25,7 @@ function SparseLinear:reset(stdv)
    if stdv then
       stdv = stdv * math.sqrt(3)
    else
-      stdv = 1./math.sqrt(self.weight:size(1))
+      stdv = 1./math.sqrt(self.weight:size(2))
    end
    if nn.oldSeed then
       for i=1,self.weight:size(1) do
@@ -40,22 +45,18 @@ function SparseLinear:updateOutput(input)
 end
 
 function SparseLinear:accGradParameters(input, gradOutput, scale)
+   if not self.lastInput then
+     self.lastInput = input:clone()
+   else
+     self.lastInput:resizeAs(input):copy(input)
+   end
+
    return input.nn.SparseLinear_accGradParameters(self, input, gradOutput, scale)
 end
 
 function SparseLinear:updateGradInput(input, gradOutput)
    if self.gradInput then
-      self.gradInput:resize(input:size())
-      self.gradInput:copy(input)
-      local numNonzero = self.gradInput:size(1)
-      for e=1,numNonzero do         
-         local g = 0
-         local i = self.gradInput[{e,1}]
-         for j=1,self.output:size(1) do
-            g = g + self.weight[{j,i}] * gradOutput[j]
-         end
-         self.gradInput[{e,2}] = g
-      end
+      input.nn.SparseLinear_updateGradInput(self, input, gradOutput)
       return self.gradInput
    end
-end
\ No newline at end of file
+end
-- 
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