[SciPy-dev] sinm and cosm for matrices with real coefficients
Robert Kern
robert.kern at gmail.com
Sun Apr 30 01:08:29 EDT 2006
Vanuxem Grégory wrote:
> Hi,
>
> The code of cosm and sinm for matrices with real coefficients can be
> improved.
>
> The actual code is something like:
>
> sinm : (expm(j * M) - expm(- j*M)) / (2 * j)
>
> cosm : (expm(j * M) + expm(- j* M)) / 2
>
> But this can be changed to (only for matrices with real coefficients):
>
> sinm : imaginary_part(expm(j * M))
>
> cosm : real_part(expm(j * M))
However, we want the functions to work on complex matrices, too. The
optimization is probably not worth the extra code to dispatch on the datatype.
Of course, if someone comes along with a use-case where they need the extra
speed, and they have a patch, unit tests, and benchmarks ready, we'd probably
put it in.
Thank you for your interest, though. Please let us know if you find anything
else that seems bogus.
--
Robert Kern
robert.kern at gmail.com
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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