There is a minor time and space saving from using x [EMAIL PROTECTED] y compared to ?x$y :
ts '? 1000 1000 $ 100' 0.0448292 8.38957e6 ts '1000 1000 [EMAIL PROTECTED] 100' 0.0292618 4.19526e6 More so for y which is a small power of 2, esp. for y=2 : ts '? 1000 1000 $ 2' 0.0143119 5.24365e6 ts '1000 1000 [EMAIL PROTECTED] 2' 0.00207931 1.04947e6 ts '? 1000 1000 $ 256' 0.0243048 8.38957e6 ts '1000 1000 [EMAIL PROTECTED] 256' 0.00988394 4.19526e6 ----- Original Message ----- From: John Randall <[EMAIL PROTECTED]> Date: Monday, January 15, 2007 8:18 am Subject: Re: [Jgeneral] Invert max and LAPACK > The addon structure is being changed from ~addons/lapack to > ~addons/math/lapack : this may cause confusion. > > load '~addons/math/lapack/lapack.ijs' > load '~addons/math/lapack/dgesv.ijs' > dgesv_z_=:dgesv_jlapack_ > testm=:3 : '(? (y,y) $ 100);=i.y' > > On my computer (32 bit Windows, 1GB) I can get (at least) up to > > dgesv testm 2000 > > before running out of memory. > > You may want to reformulate your problem: calculating inverses and > determinants is very computationally expensive and potentially > inaccurate. For example, if you want to solve Ax=b, finding the > inverse of A is not a > good way to go about it numerically. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
