wehub-resource-sync
38 lines
982 B
Python
Executable File
38 lines
982 B
Python
Executable File
import numpy as np
|
|
from prml.nn.tensor.constant import Constant
|
|
from prml.nn.tensor.tensor import Tensor
|
|
from prml.nn.function import Function
|
|
|
|
|
|
class LogDeterminant(Function):
|
|
|
|
def forward(self, x):
|
|
x = self._convert2tensor(x)
|
|
self.x = x
|
|
self._equal_ndim(x, 2)
|
|
sign, self.output = np.linalg.slogdet(x.value)
|
|
if sign != 1:
|
|
raise ValueError("matrix has to be positive-definite")
|
|
if isinstance(self.x, Constant):
|
|
return Constant(self.output)
|
|
return Tensor(self.output, function=self)
|
|
|
|
def backward(self, delta):
|
|
dx = delta * np.linalg.inv(self.x.value.T)
|
|
self.x.backward(dx)
|
|
|
|
|
|
def logdet(x):
|
|
"""
|
|
log determinant of a matrix
|
|
Parameters
|
|
----------
|
|
x : (d, d) tensor_like
|
|
a matrix to compute its log determinant
|
|
Returns
|
|
-------
|
|
output : (d, d) tensor_like
|
|
determinant of the input matrix
|
|
"""
|
|
return LogDeterminant().forward(x)
|