Inverting a 50 by 50 random matrix, aka "the JKT benchmark", has long been used in J. An example from my notebooks:
no. 5968433 filed 17.35.28 thu 13 feb 1992 from eem to kei rhui cc dhs jkt The timing David mentioned was for Joey's benchmark on the NeXT computer. The timing I reported early last year was 101.141, for NeXT using the 68030. The timing obtained last night was for J4.1 on a NeXT using a 68040, and was 19.67. ... On this machine (2.8 GHz Celeron) just now: 6!:2 '%. 50 50 [EMAIL PROTECTED] 1000' 0.00307246 ----- Original Message ----- From: Joey K Tuttle <[EMAIL PROTECTED]> Date: Monday, January 15, 2007 9:42 am Subject: Re: [Jgeneral] Invert max and LAPACK > At 12:25 -0500 2007/01/15, John Randall wrote: > >Joey K Tuttle wrote: > >> On my G5 iMac - > >> > >> x=: 1000 1000 [EMAIL PROTECTED] 0 NB. random real matrix > >> 6!:2 'y=: %. x' NB. invert it > >> 13.7781 > >> > >> >./|, (=i.1000) - x +/ .* y NB. how accurate? > >> 1.97126e_13 > >> > > > >Random matrices tend to be numerically stable. Unstable ones > crop up all > >the time. > > > > hilbert=:]\ %@(i.&.<:@+:) > > x=:hilbert 10 > > y=:%.x > > >./|, (=i.10) - x +/ .* y > >0.108042 > > > >Best wishes, > > > >John > > > > I agree/understand - but the original enquiry seemed > to be implying some kind of size limit... I was just > noting that awhile back I found it amusing/interesting > that I could invert a 1000 x 1000 matrix on my desktop > machine that is not all that much bigger than a laptop - > even with its 20 inch screen... (thinking back to the > days of machines like the IBM 3090 mainframe... :) > > - joey > > ------------------------------------------------------------------- > --- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
