How to save and recover PyBrain training?

Question

Is there a way to save and recover a trained Neural Network in PyBrain, so that I don't have to retrain it each time I run the script?

Answer 1

PyBrain's Neural Networks can be saved and loaded using either python's built in pickle/cPickle module, or by using PyBrain's XML NetworkWriter.

# Using pickle

from pybrain.tools.shortcuts import buildNetwork
import pickle

net = buildNetwork(2,4,1)

fileObject = open('filename', 'w')

pickle.dump(net, fileObject)

fileObject.close()

fileObject = open('filename','r')
net = pickle.load(fileObject)

Note cPickle is implemented in C, and therefore should be much faster than pickle. Usage should mostly be the same as pickle, so just import and use cPickle instead.

# Using NetworkWriter

from pybrain.tools.shortcuts import buildNetwork
from pybrain.tools.customxml.networkwriter import NetworkWriter
from pybrain.tools.customxml.networkreader import NetworkReader

net = buildNetwork(2,4,1)

NetworkWriter.writeToFile(net, 'filename.xml')
net = NetworkReader.readFrom('filename.xml') 

Answer 2

The NetworkWriter and NetworkReader work great. I noticed that upon saving and loading via pickle, that the network is no longer changeable via training-functions. Thus, I would recommend using the NetworkWriter-method.

Answer 3

NetworkWriter is the way to go. Using Pickle you can't retrain network as Jorg tells.

You need something like this:

from pybrain.tools.shortcuts import buildNetwork
from pybrain.tools.customxml import NetworkWriter
from pybrain.tools.customxml import NetworkReader

net = buildNetwork(4,6,1)

NetworkWriter.writeToFile(net, 'filename.xml')
net = NetworkReader.readFrom('filename.xml')