'Compute Cholesky decomposition and determine (log(det(scale)).
Parameters
scale : ndarray
Scale matrix.
Returns
c_decomp : ndarray
The Cholesky decomposition of `scale`.
logdet : scalar
The log of the determinant of `scale`.
Notes
This computation of ``logdet`` is equivalent to
``np.linalg.slogdet(scale)``.  It is ~2x faster though.'

def _cholesky_logdet(self, scale):

    c_decomp = scipy.linalg.cholesky(scale, lower=True)
    logdet = (2 * np.sum(np.log(c_decomp.diagonal())))
    return (c_decomp, logdet)
