深度学习torch之四（基于mnist数据集的实战练习实例）
1.程序运行时所需要的包，输入如下代码：
require 'torch'
require 'nn'
require 'optim'
mnist = require 'mnist' 2.载入数据集并对载入的数据集进行数据类型修改和数据的预处理：
fullset = mnist.traindataset()
testset = mnist.testdataset()
trainset = {
size = 50000,
data = fullset.data[{{1,50000}}]:double(),
label = fullset.label[{{1,50000}}]
}
validationset = {
size = 10000,
data = fullset.data[{{50001,60000}}]:double(),
label = fullset.label[{{50001,60000}}]
}
trainset.data = trainset.data - trainset.data:mean()
validationset.data = validationset.data - validationset.data:mean() model = nn.Sequential()
model:add(nn.Reshape(1, 28, 28))
model:add(nn.MulConstant(1/256.0*3.2))
model:add(nn.SpatialConvolutionMM(1, 20, 5, 5, 1, 1, 0, 0))
model:add(nn.SpatialMaxPooling(2, 2 , 2, 2, 0, 0))
model:add(nn.SpatialConvolutionMM(20, 50, 5, 5, 1, 1, 0, 0))
model:add(nn.SpatialMaxPooling(2, 2 , 2, 2, 0, 0))
model:add(nn.Reshape(4*4*50))
model:add(nn.Linear(4*4*50, 500))
model:add(nn.ReLU())
model:add(nn.Linear(500, 10))
model:add(nn.LogSoftMax())
model = require('weight-init')(model, 'xavier')5.定义损失函数：
criterion = nn.ClassNLLCriterion()
x, dl_dx = model:getParameters()
sgd_params = {
learningRate = 1e-2,
learningRateDecay = 1e-4,
weightDecay = 1e-3,
momentum = 1e-4
}
local current_loss = 0
local count = 0
local shuffle = torch.randperm(trainset.size)
batch_size = batch_size or 200
for t = 1,trainset.size,batch_size do
-- setup inputs and targets for this mini-batch
local size = math.min(t + batch_size - 1, trainset.size) - t
local inputs = torch.Tensor(size, 28, 28)--:cuda()
local targets = torch.Tensor(size)--:cuda()
for i = 1,size do
local input = trainset.data[shuffle[i+t]]
local target = trainset.label[shuffle[i+t]]
-- if target == 0 then target = 10 end
inputs[i] = input
targets[i] = target
end
targets:add(1)
local feval = function(x_new)
-- reset data
if x ~= x_new then x:copy(x_new) end
dl_dx:zero()
-- perform mini-batch gradient descent
local loss = criterion:forward(model:forward(inputs), targets)
model:backward(inputs, criterion:backward(model.output, targets))
return loss, dl_dx
end
_, fs = optim.sgd(feval, x, sgd_params)
-- fs is a table containing value of the loss function
-- (just 1 value for the SGD optimization)
count = count + 1
current_loss = current_loss + fs[1]
end
-- normalize loss
return current_loss / count
end
eval = function(dataset, batch_size)
local count = 0
batch_size = batch_size or 200
for i = 1,dataset.size,batch_size do
local size = math.min(i + batch_size - 1, dataset.size) - i
local inputs = dataset.data[{{i,i+size-1}}]
local targets = dataset.label[{{i,i+size-1}}]:long()
local outputs = model:forward(inputs)
local _, indices = torch.max(outputs, 2)
indices:add(-1)
local guessed_right = indices:eq(targets):sum()
count = count + guessed_right
end
return count / dataset.size
end
max_iters = 30
do
local last_accuracy = 0
local decreasing = 0
local threshold = 1 -- how many deacreasing epochs we allow
for i = 1,max_iters do
local loss = step()
print(string.format('Epoch: %d Current loss: %4f', i, loss))
local accuracy = eval(validationset)
print(string.format('Accuracy on the validation set: %4f', accuracy))
if accuracy < last_accuracy then
if decreasing > threshold then break end
decreasing = decreasing + 1
else
decreasing = 0
end
last_accuracy = accuracy
end
end
testset.data = testset.data:double()
eval(testset) 10.整体代码如下：
require 'torch'
require 'nn'
require 'optim'
--require 'cunn'
--require 'cutorch'
mnist = require 'mnist'
fullset = mnist.traindataset()
testset = mnist.testdataset()
trainset = {
size = 50000,
data = fullset.data[{{1,50000}}]:double(),
label = fullset.label[{{1,50000}}]
}
validationset = {
size = 10000,
data = fullset.data[{{50001,60000}}]:double(),
label = fullset.label[{{50001,60000}}]
}
trainset.data = trainset.data - trainset.data:mean()
validationset.data = validationset.data - validationset.data:mean()
model = nn.Sequential()
model:add(nn.Reshape(1, 28, 28))
model:add(nn.MulConstant(1/256.0*3.2))
model:add(nn.SpatialConvolutionMM(1, 20, 5, 5, 1, 1, 0, 0))
model:add(nn.SpatialMaxPooling(2, 2 , 2, 2, 0, 0))
model:add(nn.SpatialConvolutionMM(20, 50, 5, 5, 1, 1, 0, 0))
model:add(nn.SpatialMaxPooling(2, 2 , 2, 2, 0, 0))
model:add(nn.Reshape(4*4*50))
model:add(nn.Linear(4*4*50, 500))
model:add(nn.ReLU())
model:add(nn.Linear(500, 10))
model:add(nn.LogSoftMax())
model = require('weight-init')(model, 'xavier')
criterion = nn.ClassNLLCriterion()
--model = model:cuda()
--criterion = criterion:cuda()
--trainset.data = trainset.data:cuda()
--trainset.label = trainset.label:cuda()
--validationset.data = validationset.data:cuda()
--validationset.label = validationset.label:cuda()
sgd_params = {
learningRate = 1e-2,
learningRateDecay = 1e-4,
weightDecay = 1e-3,
momentum = 1e-4
}
x, dl_dx = model:getParameters()
step = function(batch_size)
local current_loss = 0
local count = 0
local shuffle = torch.randperm(trainset.size)
batch_size = batch_size or 200
for t = 1,trainset.size,batch_size do
-- setup inputs and targets for this mini-batch
local size = math.min(t + batch_size - 1, trainset.size) - t
local inputs = torch.Tensor(size, 28, 28)--:cuda()
local targets = torch.Tensor(size)--:cuda()
for i = 1,size do
local input = trainset.data[shuffle[i+t]]
local target = trainset.label[shuffle[i+t]]
-- if target == 0 then target = 10 end
inputs[i] = input
targets[i] = target
end
targets:add(1)
local feval = function(x_new)
-- reset data
if x ~= x_new then x:copy(x_new) end
dl_dx:zero()
-- perform mini-batch gradient descent
local loss = criterion:forward(model:forward(inputs), targets)
model:backward(inputs, criterion:backward(model.output, targets))
return loss, dl_dx
end
_, fs = optim.sgd(feval, x, sgd_params)
-- fs is a table containing value of the loss function
-- (just 1 value for the SGD optimization)
count = count + 1
current_loss = current_loss + fs[1]
end
-- normalize loss
return current_loss / count
end
eval = function(dataset, batch_size)
local count = 0
batch_size = batch_size or 200
for i = 1,dataset.size,batch_size do
local size = math.min(i + batch_size - 1, dataset.size) - i
local inputs = dataset.data[{{i,i+size-1}}]--:cuda()
local targets = dataset.label[{{i,i+size-1}}]:long()--:cuda()
local outputs = model:forward(inputs)
local _, indices = torch.max(outputs, 2)
indices:add(-1)
local guessed_right = indices:eq(targets):sum()
count = count + guessed_right
end
return count / dataset.size
end
max_iters = 30
do
local last_accuracy = 0
local decreasing = 0
local threshold = 1 -- how many deacreasing epochs we allow
for i = 1,max_iters do
local loss = step()
print(string.format('Epoch: %d Current loss: %4f', i, loss))
local accuracy = eval(validationset)
print(string.format('Accuracy on the validation set: %4f', accuracy))
if accuracy < last_accuracy then
if decreasing > threshold then break end
decreasing = decreasing + 1
else
decreasing = 0
end
last_accuracy = accuracy
end
end
testset.data = testset.data:double()
eval(testset) 11.如此所有的工作就完成了，运行代码，输出如图结果：
