The Mathieu functions can be computed for a single order or
for multiple orders, using array-based routines. The array-based
routines require a preallocated workspace.
— Function: gsl_sf_mathieu_workspace *
gsl_sf_mathieu_alloc (
size_t n, double qmax)
This function returns a workspace for the array versions of the
Mathieu routines. The arguments n and qmax specify the
maximum order and q-value of Mathieu functions which can be
computed with this workspace.