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square.py
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square.py
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from chainer import backend
from chainer import function_node
from chainer import utils
from chainer.utils import type_check
class Square(function_node.FunctionNode):
@property
def label(self):
return 'square'
def check_type_forward(self, in_types):
type_check._argname(in_types, ('x',))
type_check.expect(in_types[0].dtype.kind == 'f')
def forward(self, x):
self.retain_inputs((0,))
xp = backend.get_array_module(*x)
return utils.force_array(xp.square(x[0], dtype=x[0].dtype)),
def backward(self, indexes, gy):
x = self.get_retained_inputs()[0]
gx = gy[0] * 2.0 * x
return gx,
def square(x):
"""Elementwise square function.
.. math::
y_i = x_i ^ 2.
Args:
x (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
Returns:
~chainer.Variable: Output variable.
"""
return Square().apply((x,))[0]