Re: How to speed up this calculation?

*To*: mathgroup at smc.vnet.net*Subject*: [mg37211] Re: How to speed up this calculation?*From*: "Steve Luttrell" <luttrell at _removemefirst_westmal.demon.co.uk>*Date*: Thu, 17 Oct 2002 00:08:28 -0400 (EDT)*References*: <aokc15$agm$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Cases[pairs, _?(#[[1]] != #[[2]] &)] does what you want. -- Steve Luttrell West Malvern, UK "Cheng Liu" <cliu at lanl.gov> wrote in message news:aokc15$agm$1 at smc.vnet.net... > Dear group, > > I have the following question regarding a lengthy calculation > using Mathematica: > > For given w points in x direction and h points in y direction, I can > construct all the points using > > h=10; w=8; > points=Flatten[Transpose[Outer[List,Range[w],Range[h]]],1] > > Next, I need to find all the possible pairs of point including points > themselves, i.e., pair AA. I can use > > pairs=Outer[List,points,points,1] > > Then, I have to clear those pairs that repeat themselves, i.e., pair AB and > pair BA. Also, when w and h are of the order of 1000s, the computation > takes a very long time. Is there a better way of doing the second part of > the computation? Thanks in advance. > > Sincerely > > Cheng > > > ==================================================== > Cheng Liu, Ph.D. > MST-8, Structure/Property Relations > Materials Science and Technology Division > Los Alamos National Laboratory > Los Alamos, New Mexico 87545 > > Phone: 505-665-6892 (office), 505-667-9950 (lab) > Fax: 505-667-8021 > email: cliu at lanl.gov > ==================================================== > >