torch simple neural network

linear.lua

# reference https://ckmarkoh.github.io/blog/2017/01/01/torch-nn-tutorial-4-backward-propagation/

# we want to learn y=x+1

require 'nn'
y = torch.Tensor(5)
mlp = nn.Sequential()
mlp:add(nn.Add(5))

function gradUpdate(mlp, x, y, criterion, learningRate)
   local pred = mlp:forward(x)
   local err = criterion:forward(pred, y)
   local gradCriterion = criterion:backward(pred, y)
   mlp:zeroGradParameters()
   mlp:backward(x, gradCriterion)
   mlp:updateParameters(learningRate)
   return err
end

for i = 1, 20 do
   print (i)
   x = torch.rand(5)
   y:copy(x);
   for i = 1, 5 do y[i] = y[i] + i; end
   err = gradUpdate(mlp, x, y, nn.MSECriterion(), 0.01)
end

print(mlp:get(1).bias)