Re: How to avoid repeated recalculation of the same function

*To*: mathgroup at smc.vnet.net*Subject*: [mg132674] Re: How to avoid repeated recalculation of the same function*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Sat, 3 May 2014 03:40:15 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <20140502061856.7A2216A46@smc.vnet.net>

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 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 > >

**References**:**How to avoid repeated recalculation of the same function***From:*pgeipi10@gmail.com