Source code for chainer.links.connection.linear

import math

from chainer import cuda
from chainer.functions.connection import linear
from chainer import initializers
from chainer import link

[docs]class Linear(link.Link): """Linear layer (a.k.a. fully-connected layer). This is a link that wraps the :func:`~chainer.functions.linear` function, and holds a weight matrix ``W`` and optionally a bias vector ``b`` as parameters. The weight matrix ``W`` is initialized with i.i.d. Gaussian samples, each of which has zero mean and deviation :math:`\\sqrt{1/\\text{in_size}}`. The bias vector ``b`` is of size ``out_size``. Each element is initialized with the ``bias`` value. If ``nobias`` argument is set to True, then this link does not hold a bias vector. Args: in_size (int): Dimension of input vectors. If ``None``, parameter initialization will be deferred until the first forward data pass at which time the size will be determined. out_size (int): Dimension of output vectors. wscale (float): Scaling factor of the weight matrix. bias (float): Initial bias value. nobias (bool): If ``True``, then this function does not use the bias. initialW (2-D array): Initial weight value. If ``None``, then this function uses Gaussian distribution scaled by ``w_scale`` to initialize weight. May also be a callable that takes ``numpy.ndarray`` or ``cupy.ndarray`` and edits its value. initial_bias (1-D array): Initial bias value. If ``None``, then this function uses ``bias`` to initialize bias. May also be a callable that takes ``numpy.ndarray`` or ``cupy.ndarray`` and edits its value. .. seealso:: :func:`~chainer.functions.linear` Attributes: W (~chainer.Variable): Weight parameter. b (~chainer.Variable): Bias parameter. """ def __init__(self, in_size, out_size, wscale=1, bias=0, nobias=False, initialW=None, initial_bias=None): super(Linear, self).__init__() # For backward compatibility self.initialW = initialW self.wscale = wscale self.out_size = out_size # For backward compatibility, the scale of weights is proportional to # the square root of wscale. self._W_initializer = initializers._get_initializer( initialW, math.sqrt(wscale)) if in_size is None: self.add_uninitialized_param('W') else: self._initialize_params(in_size) if nobias: self.b = None else: if initial_bias is None: initial_bias = bias bias_initializer = initializers._get_initializer(initial_bias) self.add_param('b', out_size, initializer=bias_initializer) def _initialize_params(self, in_size): self.add_param('W', (self.out_size, in_size), initializer=self._W_initializer) def __call__(self, x): """Applies the linear layer. Args: x (~chainer.Variable): Batch of input vectors. Returns: ~chainer.Variable: Output of the linear layer. """ if self.has_uninitialized_params: with cuda.get_device(self._device_id): self._initialize_params(x.size // x.shape[0]) return linear.linear(x, self.W, self.b)