Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Another Out of Memory Problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg91314] Re: Another Out of Memory Problem
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Fri, 15 Aug 2008 06:53:06 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <g8137j$19$1@smc.vnet.net>

Kevin J. McCann wrote:

> I can do the following:
> 
> Integrate[Cos[2*x]*
>       Exp[I*z*Cos[x]],
>     {x, -Pi, Pi}]
> 
> 
> which produces a Bessel function answer; however if I change the
> argument in the cosine to 2.5 as in:
> 
> Integrate[Cos[2.5*x]*
>       Exp[I*z*Cos[x]],
>     {x, -Pi, Pi}]
> 
> I almost immediately get this:
> 
> No more memory available.
> Mathematica kernel has shut down.
> Try quitting other applications and then retry.
> 
> Any ideas why? I am running XP with 2Gb of memory.

When using symbolic function (i.e. Integrate rather than NIntegrate, 
Solve rather than NSolve, etc.) it is always a good idea to feed the 
function with *exact* (infinite precision) numbers, thus 5/2 rather 2.5 
in your case. (Mathematica does not find any closed form for your 
integrand. Note that it take a while to compute but memory consumption 
is under control.)

In[1]:= Integrate[Cos[5/2*x]*Exp[I*z*Cos[x]], {x, -Pi, Pi}]

Out[1]=

            I z Cos[x]     5 x
Integrate[E           Cos[---], {x, -Pi, Pi}]
                            2

Regards,
-- Jean-Marc


  • Prev by Date: Re: Another Out of Memory Problem
  • Next by Date: Re: ODE in mathematica. what is wrong?
  • Previous by thread: Re: Another Out of Memory Problem
  • Next by thread: Re: Another Out of Memory Problem