How to speed up this calculation?
- To: mathgroup at smc.vnet.net
- Subject: [mg37200] How to speed up this calculation?
- From: Cheng Liu <cliu at lanl.gov>
- Date: Wed, 16 Oct 2002 14:26:20 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
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
====================================================