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Re: NIntegrate with AdaptiveMonteCarlo gives different results

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  • Subject: [mg123338] Re: NIntegrate with AdaptiveMonteCarlo gives different results
  • From: valentina <fuchi8 at tiscali.it>
  • Date: Fri, 2 Dec 2011 07:20:40 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <jb7u17$jr5$1@smc.vnet.net>

On Dec 1, 2:04 pm, valentina <fuc... at tiscali.it> wrote:
> Hello everybody,
> I am dealing with a three dimensional integral and I am using
> NIntegrate. Searching the web I found out that the best method is the
> AdaptiveMonteCarlo, which also speed up the calculation.
> this is the integral, no particular singular points:
>
> test[d_] := (0.5  NIntegrate[(compnx[x, y, z, d] +
>        compny[x, y, z, d] + compnz[x, y, z, d]), {z, -R - d/2,
>       R + d/2}, {x, -R, R}, {y, -R, R},
>      Method -> "MultiDimensionalRule"]*hc) // Timing
>
> so I want to calculate it for different values of the parameter d, but
> for example if I successively calculate it for d=4 i get two different
> results which differs of about 30-50 MeV.
>
> Does anyone know if it is a bug or how could I fix it?
>
> Thanks in advance.

Sorry,
I did not tell everything about the integrand.
x,y,z are the Cartesian coordinate, so I am dealing with three
dimensional functions, smooth function imagine like having two smooth
peaks centered in a symmetric way around (0,0,0). Just when both x and
y are equal to zero i have singularities but NIntegrate seems to deal
with them because without specifying the method, it took hours, but i
get the correct result.
hc is a physical constant, namely 197.3 MeV fm, so it's a number just
to have the result in energy dimension.
Should I specify more options when calling the AdaptiveMonteCarlo?

thanks  and sorry again for my lack of informations



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