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Re: How to avoid repeated recalculation of the same

  • To: mathgroup at smc.vnet.net
  • Subject: [mg132678] Re: How to avoid repeated recalculation of the same
  • From: Alex Krasnov <akrasnov at cory.eecs.berkeley.edu>
  • Date: Sat, 3 May 2014 03:41:35 -0400 (EDT)
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  • References: <20140502061856.7A2216A46@smc.vnet.net>

Mathematica makes memoization easy. You can store the result directly in 
the function definition using the idiom f[x_] := f[x] = (...). You can 
then examine the stored results using Information[f].

Alex


On Fri, 2 May 2014, pgeipi10 at 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
>



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