comp.lang.idl-pvwave archive: archive » Re: limits of 'invert'

Home » Public Forums » archive » Re: limits of 'invert'

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: limits of 'invert' [message #46340 is a reply to message #46338]

Wed, 16 November 2005 11:07

K. Bowman
Messages: 330
Registered: May 2000

Senior Member

In article <1132162119.050786.109730@g47g2000cwa.googlegroups.com>,
"queiny" <queiny98@yahoo.com> wrote:

> Dear IDL & Maths experts:
>
> Is there a limit for the 'invert' or 'la_invert', program to calculate
> the inversion of a square matrix, provided by IDL?
>
> When my matrix is 150x150, 'invert' return immediatelly, but when it is
> '15000x15000', 'invert' runs for more than a day. I am wondering
> whether it is in some infinite loop, or it simply needs that long.
>
> What is the reasonable upper limit that 'invert' or 'la_inver' can
> operate?
>
> Thanks,
>
> Q

Matrix inversion is an O(n^3) operation, so the second case should require
~100^3 times as long as the first, that is, ~10^6 times as long. (There are
~10^5 seconds/day.)

Also, storing a 15000 x 15000 array requires ~900 MB, so you may very well be
swapping to disk, which will slow things down by another couple of orders of
magnitude.

I suggest that you consult a good introductory numerical analysis book.

Cheers, Ken Bowman

Report message to a moderator

[Message index]

		Re: limits of 'invert' By: Paolo Grigis on Thu, 17 November 2005 00:38
		Re: limits of 'invert' By: queiny on Wed, 16 November 2005 12:16
		Re: limits of 'invert' By: K. Bowman on Wed, 16 November 2005 11:07
		Re: limits of 'invert' By: Foldy Lajos on Wed, 16 November 2005 10:01

Previous Topic:	IDLgrPolygon -TEXTURE_MAP question
Next Topic:	lunch envi function in 'batch mode'

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun Nov 30 15:58:50 PST 2025

Total time taken to generate the page: 0.23868 seconds