scipy.sparse.linalg._matfuncs:_exp_sinch

Notes

The strategy of falling back to a sixth order Taylor expansion was suggested by the Spallation Neutron Source docs which was found on the internet by google search. http://www.ornl.gov/~t6p/resources/xal/javadoc/gov/sns/tools/math/ElementaryFunction.html The details of the cutoff point and the Horner-like evaluation was picked without reference to anything in particular.

Note that sinch is not currently implemented in scipy.special, whereas the "engineer's" definition of sinc is implemented. The implementation of sinc involves a scaling factor of pi that distinguishes it from the "mathematician's" version of sinc.