Re: How to avoid repeated recalculation of the same function

Path	csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!usenet.blueworldhosting.com!feeder01.blueworldhosting.com!news.alt.net!nx01.iad01.newshosting.com!newshosting.com!newspump.sol.net!post2.nntp.sol.net!posts.news.twtelecom.net!nnrp3.twtelecom.net!not-for-mail
From	Bob Hanlon <hanlonr357@gmail.com>
Newsgroups	comp.soft-sys.math.mathematica
Subject	Re: How to avoid repeated recalculation of the same function
Date	Sat, 3 May 2014 07:40:33 +0000 (UTC)
Sender	steve@smc.vnet.net
Approved	Steven M. Christensen <steve@smc.vnet.net>, Moderator
Message-ID	<lk26hh$123$1@smc.vnet.net> (permalink)
References	<20140502061856.7A2216A46@smc.vnet.net>
Lines	38
Organization	Time-Warner Telecom
NNTP-Posting-Date	03 May 2014 07:46:47 GMT
NNTP-Posting-Host	34e5c530.news.twtelecom.net
X-Trace	DXC=5XTl[dHb:LdnJ]SQJ40F_gC_A=>8kQj6m;[h;PUXBgbdAQ5nGY>YK1nEFiONJ7[GofUhmQ9<QeDYk
X-Complaints-To	abuse@twtelecom.net
Xref	csiph.com comp.soft-sys.math.mathematica:16894

Show key headers only | View raw

If the calculation can be done symbolicly use f[x_] = calc rather than
f[x_] := calc

You may also want to [Full]Simplify the expression, i.e., f[x_] = Simplify[
calc, assumptions ] to speed up subsequent use as well as improve numerical
precision.


Bob Hanlon



On Fri, May 2, 2014 at 2:18 AM, <pgeipi10@gmail.com> wrote:

> Hi,
>
> I'm doing a calculaton that's purly symbolic (no graphing, numerical
> integration, etc.).
>
> Suppose I have a function f[x_]:=... that's very complex to build. In
> fact, f[x] ends up being a manageable expression (about 30 characters) but
> it takes Mathematica about 30 min to build that expression.
>
> Another function g[] uses the function f[x] and references it many times.
> I've discovered that g[] actually builds f[x] every time it's referenced
> which takes 30 minutes each time. Theoretically, Mathematica could build it
> once and then use the resulting expression every time it's referenced.
>
> So how do I accomplish that? That is, how do I make it build f[x] once and
> then use the resulting expression when it's needed?
>
> Thanks,
>
>
> Pavel
>
>

Back to comp.soft-sys.math.mathematica | Previous | Next | Find similar

Thread

Re: How to avoid repeated recalculation of the same function Bob Hanlon <hanlonr357@gmail.com> - 2014-05-03 07:40 +0000

csiph-web