Re: Where's the Speed?
- To: mathgroup at smc.vnet.net
- Subject: [mg19962] Re: Where's the Speed?
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Thu, 23 Sep 1999 23:26:16 -0400
- Organization: University of Western Australia
- References: <7s1p4h$9n0@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Robert Knapp wrote:
> Timing[U2 = NestWhileList[Crank2, U[[1]], True &, 1, Nt - 1];]
>
> {1.69 Second, Null}
>
> There are two important features of the new code worth mentioning, both
> involving features new to version 4
>
> First, the use of NestWhileList. If you have a loop which uses Append
> to accumulate a result, Mathematica has to make an extra copy of the
> whole result each time through the loop. If you loop many times, this
> can have a big effect on your overall timing.
Surely NestWhileList is not needed here. You can just use NestList in
this example:
U2 = NestList[Crank2, U[[1]], Nt - 1];
Also to Kevin, Crank-Nicholson should be Crank-Nicolson. Numerical
Recipes amongst many others gets this wrong.
The reference is (in BibTeX format)
@ARTICLE{crank-nicol,
AUTHOR="Crank, J. and Nicolson, P.",
YEAR="1947",
TITLE="A Practical Method for Numerical Evaluation of "
# "Solutions of Partial Differential Equations of the "
# "Heat-Conduction Type",
JOURNAL="Proceedings of the Cambridge Philosophical Society",
VOLUME="43",
PAGES="50-67"
}
The misunderstanding over the spelling probably arose because in the
original journal the spelling on the contents page differs from that at
the top of the paper.
Cheers,
Paul
____________________________________________________________________
Paul Abbott Phone: +61-8-9380-2734
Department of Physics Fax: +61-8-9380-1014
The University of Western Australia
Nedlands WA 6907 mailto:paul at physics.uwa.edu.au
AUSTRALIA http://physics.uwa.edu.au/~paul
God IS a weakly left-handed dice player
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