/
squared_error.py
53 lines (38 loc) · 1.4 KB
/
squared_error.py
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from chainer import function_node
from chainer import utils
from chainer.utils import type_check
class SquaredError(function_node.FunctionNode):
"""Squared error function."""
def check_type_forward(self, in_types):
type_check._argname(in_types, ('x0', 'x1'))
type_check.expect(
in_types[0].dtype.kind == 'f',
in_types[0].dtype == in_types[1].dtype,
in_types[0].shape == in_types[1].shape
)
def forward(self, inputs):
x0, x1 = inputs
diff = x0 - x1
self.retain_inputs((0, 1))
return utils.force_array(diff * diff, dtype=x0.dtype),
def backward(self, indexes, grad_outputs):
x0, x1 = self.get_retained_inputs()
gy, = grad_outputs
gx = gy * 2 * (x0 - x1)
return gx, -gx
def squared_error(x0, x1):
"""Squared error function.
This function computes the squared error between two variables:
.. math::
(x_0 - x_1)^2
where operation is done in elementwise manner.
Note that the error is not scaled by 1/2:
Args:
x0 (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
x1 (:class:`~chainer.Variable` or :ref:`ndarray`): Input variable.
Returns:
~chainer.Variable:
A variable holding an array representing the squared error of
two inputs.
"""
return SquaredError().apply((x0, x1))[0]