[SciPy-dev] Removing globals from minpack wrapper
Travis E. Oliphant
Thu Jun 26 03:15:41 CDT 2008
Yosef Meller wrote:
> I was having my fun with optimize.fsolve() at work, when I realized
> that both the Python side and the C/FORTRAN side allocate work spaces,
> and then copy between them, which seemed wasteful. I started playing
> around with the code to try and create a version that allows the same
> buffer to move around between Python and minpack.
> I couldn't do that (and I doubt now that it's possible), but on the
> way I found a method to remove the global variables that are used to
> store the data needed by the multipack functions but not passed in by
> the FORTRAN code which doesn't even know about it.
> The trick was to allocate extra space on the work buffers and use it
> as a pointer to a structure that contains the information. This may
> seem just as ugly, but it has all the advantages of not using globals,
> including the prospects of someday making it thread-safe.
> The attached patch implements the trick in minpack_hybrj, and the
> Python code tests that it works.
> Do you think it's worth doing to the rest of the minpack functions?
That is pretty clever. Amy I correct that the only time cost is an
extra array allocation (for ap_fvec) per complete calla?
I think it is worth it. Using globals requires a bit of rigging to
support re-entrance of the optimizers (so you could have a python
function that itself calls optimize).
Thanks for looking at the code.
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