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Re: question for compiling a function

• To: mathgroup at smc.vnet.net
• Subject: [mg113148] Re: question for compiling a function
• From: Ray Koopman <koopman at sfu.ca>
• Date: Fri, 15 Oct 2010 13:51:48 -0400 (EDT)
• References: <i95tjc$65h$1@smc.vnet.net>

On Oct 13, 8:31 pm, Ramiro <ramiro.barran... at gmail.com> wrote:
> Hello,
>
> I am doing some MCMC on mathematica and performance is becoming an
> issue.  So the low hanging fruit would be compiling some functions.
> Below is an portion of the key one:
>
> example[n_, \[Alpha]_] :=
>  Gamma[Plus @@ n + \[Alpha]]/Times @@ (Gamma[# + 1] & /@ n)
>
> "n" is a vector of positive reals.  However, I don't know how big it
> is, it will usually be just 4 o 5 numbers but could be anything from 1
> to 200 size vector.
>
> Any suggestions?
>
> Thanks in advance,
> Ramiro

xample[n,\[Alpha]] == Multinomial@@n * Pochhammer[1.+Tr@n,\[Alpha]-1.]