The standard approach to evaluate Hecke eigenvalues of a Siegel modular eigenform
is to determine a large number of Fourier coefficients of
and then
compute the Hecke action on those coefficients. We present a new method based on the numerical
evaluation of
at explicit points in the upper half-space and of its image under the Hecke operators.
The approach is more efficient than the standard method and has the potential for
further optimization by identifying good candidates for the points of evaluation, or
finding ways of lowering the truncation bound. A limitation of the algorithm
is that it returns floating point numbers for the eigenvalues; however, the
working precision can be adjusted at will to yield as close an approximation as
needed.