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Re: memory allocation on Macs [message #61045 is a reply to message #60098]

Thu, 26 June 2008 13:54

wlandsman
Messages: 743
Registered: June 2000

Senior Member

> Then... second... any tips on getting around gigantic memory issues?
> I'm running into them using the Goddard astron library for coordinate
> transformations. The big problem is (at least partly) that my very
> large float arrays get converted into doubles because all of the
> astron packages use doubles. There's no way to force the arrays to
> stay in the smaller version, right?

It's somewhat odd to be carrying all your coordinates in a big
array. Usually one has a world coordinate system (e.g. in a FITS
header) from which one can compute the coordinate of every pixel.
One can then precess, rotate, or otherwise transform the coordinate
system without applying the transformation to each individual
pxiel.

But presuming you need to work with arrays of coordinates, you can
always transform the result back to float. For example, if you have
big celestial coordinates arrays, ra and dec, that you need to
transform to Galactic then use euler.pro

IDL> euler,1,ra,dec,glong,glat ;Glong and glat are always output
double precision
IDL> glong=float(glong) & glat = float(glat) ;so convert back to
float

Also think about whether you need to keep old variables. For
example,

IDL> euler,1,ra,dec ;Convert ra,dec to Galactic
IDL> glong = float(temporary(ra) ) & glat = float(temporary(dec))

--Wayne

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[Message index]

		memory allocation on Macs By: pgrigis on Thu, 01 May 2008 09:18
		Re: memory allocation on Macs By: pgrigis on Mon, 05 May 2008 13:49
		Re: memory allocation on Macs By: Keflavich on Thu, 26 June 2008 12:14
		Re: memory allocation on Macs By: dcleon@gmail.com on Mon, 05 May 2008 06:49
		Re: memory allocation on Macs By: henrygroe on Sat, 03 May 2008 07:20
		Re: memory allocation on Macs By: wlandsman on Fri, 27 June 2008 06:40
		Re: memory allocation on Macs By: Keflavich on Thu, 26 June 2008 16:43
		Re: memory allocation on Macs By: wlandsman on Thu, 26 June 2008 13:54

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