import logging,lasagne
import numpy as np
import theano.tensor as T
logging.basicConfig()
logger= logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
# adapted from https://github.com/nouiz/lisa_emotiw/blob/master/emotiw/wardefar/crf_theano.py
def theano_logsumexp(x, axis=None):
"""
Compute log(sum(exp(x), axis=axis) in a numerically stable
fashion.
Parameters
----------
x : tensor_like
A Theano tensor (any dimension will do).
axis : int or symbolic integer scalar, or None
Axis over which to perform the summation. `None`, the
default, performs over all axes.
Returns
-------
result : ndarray or scalar
The result of the log(sum(exp(...))) operation.
"""
xmax = T.max(x,axis=axis, keepdims=True)
xmax_ = T.max(x,axis=axis)
return xmax_ + T.log(T.exp(x - xmax).sum(axis=axis))
