[AstroPy] TAN WCS speedup

[Michael Droettboom]

That is correct.  WCSLIB C code is single-threaded.  It's a relatively 
straightforward calculation such that I'd be surprised if anything else 
could account for such a large speedup.

Mike

On 11/13/2014 04:12 PM, Kyle Barbary wrote:
> I'm curious if part of the speed up is due to using two cores in the 
> numexpr version? I assume the WCSLIB C code is not threaded.
>
> - Kyle
>
> On Thu, Nov 13, 2014 at 12:43 PM, Maik Riechert 
> <maik.riechert at arcor.de <mailto:maik.riechert at arcor.de>> wrote:
>
>     Hi,
>
>     I just finished implementing my own wcs_pix2world function
>     specifically
>     for the TAN projection using just Python with numpy and numexpr.
>     Without
>     numexpr I was slightly slower than astropy (15s vs 12.8s). But with
>     numexpr I got it down to 6.8s, so nearly twice as fast. This is for 8
>     million pixel coordinates as input run on my 2GHz Core 2 Duo Laptop
>     under Python 2.7 64 bit with Windows 7 and using Christoph Gohlke's
>     numpy and numexpr binaries.
>
>     I cannot post the code yet but the code is not that important
>     anyway as
>     I didn't do really complicated things.
>
>     As numexpr seems to provide the main speedup, maybe some concepts
>     of it
>     could be used to speedup astropy/wcslib. I guess it's not a sensible
>     option to actually implement all of wcslib in Python, given that there
>     are way more complicated projections etc. than TAN which would take
>     quite some time to reimplement/maintain.
>
>     This is basically it, just wanted to share that.
>
>     Cheers
>     Maik
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-- 
Michael Droettboom
Science Software Branch
Space Telescope Science Institute

http://www.droettboom.com

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