有没有办法在不重新编译Theano的情况下更改函数的更新列表? [英] Is there a way to change a function's update list without re-compiling it in Theano?
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问题描述
我在范围内(iter_num):
learn_rate = i * alpha
do_training学习速度,......)
显然,为每次迭代重新编译一个新函数将会太慢。
所以我想知道在Theano中有更好的方法吗?
Thanks!
解决方案
您可以将学习率设为符号变量,并将其传递到如下所示的训练函数中:
进口numpy
进口theano
将theano.tensor导入为t
def compile(input_size,hidden_size,output_size):
W_h = theano.shared(numpy.random.standard_normal(size =(input_size,hidden_size))。astype(theano.config.floatX))
b_h = theano.shared(numpy.zeros((hidden_size,),dtype = theano.config.floatX))
W_y = theano.shared(numpy.random.standard_normal(size =(hidden_size,output_size)) .astype(theano.config.floatX))
b_y = theano.shared(numpy.zeros((output_size,),dtype = theano.config.floatX))
x = tt.matrix ('x')
z = tt.ivector('z')
learning_rate = tt.scalar()
h = tt.tanh(theano.dot(x,W_h)+ b_h)
y = tt.nnet.softmax(theano.dot(h,W_y)+ b_y)
cost = tt.nnet.categorical_crossentropy(y, z).mean()
updates = [(p,p - learning_rate * tt.grad(cost,p))for p in(W_h,b_h,W_y,b_y)]
return theano.function ([x,z,learning_rate],outputs = cost,updates = updates)
$ b def main():
input_size = 5
hidden_size = 4
output_size = 3
train = compile(input_size,hidden_size,output_size)
print train([[0,1,2,3,4],[5,6,7,8,9] ],[1,2],0.1)
main()
请注意,训练功能现在有三个参数;第三是学习率。
Indeed I want to change the learning rate at different periods of training. Something like:
for i in range(iter_num):
learn_rate = i*alpha
do_training(learn_rate,...)
Apparently recompiling a new function for every iteration is going to be too slow. So I was wondering is there a better way to do it in Theano? Thanks!
解决方案
You can make the learning rate a symbolic variable and pass it into the training function like this:
import numpy
import theano
import theano.tensor as tt
def compile(input_size, hidden_size, output_size):
W_h = theano.shared(numpy.random.standard_normal(size=(input_size, hidden_size)).astype(theano.config.floatX))
b_h = theano.shared(numpy.zeros((hidden_size,), dtype=theano.config.floatX))
W_y = theano.shared(numpy.random.standard_normal(size=(hidden_size, output_size)).astype(theano.config.floatX))
b_y = theano.shared(numpy.zeros((output_size,), dtype=theano.config.floatX))
x = tt.matrix('x')
z = tt.ivector('z')
learning_rate = tt.scalar()
h = tt.tanh(theano.dot(x, W_h) + b_h)
y = tt.nnet.softmax(theano.dot(h, W_y) + b_y)
cost = tt.nnet.categorical_crossentropy(y, z).mean()
updates = [(p, p - learning_rate * tt.grad(cost, p)) for p in (W_h, b_h, W_y, b_y)]
return theano.function([x, z, learning_rate], outputs=cost, updates=updates)
def main():
input_size = 5
hidden_size = 4
output_size = 3
train = compile(input_size, hidden_size, output_size)
print train([[0, 1, 2, 3, 4], [5, 6, 7, 8, 9]], [1, 2], 0.1)
main()
Note that the training function now has three parameters; the third is the learning rate.
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