scikit-chainer

scikit-learn like interface to chainer

How to install

$ pip install scikit-chainer

what's this?

This is a scikit-learn like interface to the chainer deeplearning framework. You can use it to build your network model and use the model with scikit-learn APIs (e.g. fit, predict) There are ChainerRegresser for regression, ChainerClassifer for classification base classes and ChainerTransformer for transformation. You need to inherit them and implement the following functions,

1. _setup_network : network definition (FunctionSet, Chain or ChainList of chainer)
2. forward : emit the result z input x (note this is not the final predicted value)
3. loss_func: the loss function to minimize (e.g. mean_squared_error, softmax_cross_entropy etc)
4. output_func : emit the final result y from forwarded values z (e.g. identity for regression and softmax for classification.

Example

Linear Regression

class LinearRegression(ChainerRegresser):
    def _setup_network(self, **params):
        return Chain(l1=F.Linear(params["n_dim"], 1))

    def forward(self, x):
        y = self.network.l1(x)
        return y

    def loss_func(self, y, t):
        return F.mean_squared_error(y, t)

    def output_func(self, h):
        return F.identity(h)

LogisticRegression

class LogisticRegression(ChainerClassifier):
    def _setup_network(self, **params):
        return Chain(l1=F.Linear(params["n_dim"], params["n_class"]))

    def forward(self, x):
        y = self.network.l1(x)
        return y

    def loss_func(self, y, t):
        return F.softmax_cross_entropy(y, t)

    def output_func(self, h):
        return F.softmax(h)

AutoEncoder

class AutoEncoder(ChainerTransformer):
    def __init__(self, activation=F.relu, **params):
        super(ChainerTransformer, self).__init__(**params)
        self.activation = activation

    def _setup_network(self, **params):
        return Chain(
            encoder=F.Linear(params["input_dim"], params["hidden_dim"]),
            decoder=F.Linear(params["hidden_dim"], params["input_dim"])
        )

    def _forward(self, x, train=False):
        z = self._transform(x, train)
        y = self.network.decoder(z)
        return y

    def _loss_func(self, y, t):
        return F.mean_squared_error(y, t)

    def _transform(self, x, train=False):
        return self.activation(self.network.encoder(x))