Groups > comp.lang.java.programmer > #9332

RandomDirichlet?

From	Giovanni Azua <bravegag@hotmail.com>
Newsgroups	comp.lang.java.programmer
Subject	RandomDirichlet?
Date	2011-11-01 10:09 +0100
Message-ID	<CAD575DC.8551%bravegag@hotmail.com> (permalink)

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Hello,

I need to generate random TPCH workloads but I don't want a Uniform
distribution where Q1, RF1, RF2 would be equally probable i.e. using new
Random().nextInt(..)

I instead would like to draw samples from a Dirichlet distribution which
would give a very skewed PD depending on the input alphas (which specify how
skewed I want the PD to be). The Matlab code would be exactly:

function r = dirichlet_sample(a,n)
p = length(a);
r = gamrnd(repmat(a,n,1),1,n,p);
r = r ./ repmat(sum(r,2),1,p);
End

But there is no "gamrnd" RandomGamma in Java nor RandomDirichlet. Before I
spend time writing this, can anyone advice for a low-footprint library
implementing those functions?

TIA,
Best regards,
Giovanni

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RandomDirichlet? Giovanni Azua <bravegag@hotmail.com> - 2011-11-01 10:09 +0100
  Re: RandomDirichlet? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-01 07:50 -0400
    Re: RandomDirichlet? Giovanni Azua <bravegag@hotmail.com> - 2011-11-01 19:50 +0100
  Re: RandomDirichlet? Wojtek <nowhere@a.com> - 2011-11-01 04:54 -0700
  Re: RandomDirichlet? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-01 06:11 -0700
    Re: RandomDirichlet? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-01 06:16 -0700
    Re: RandomDirichlet? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-01 20:23 -0400
      Re: RandomDirichlet? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-02 01:39 -0700
        Re: RandomDirichlet? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-02 08:17 -0400
  Re: RandomDirichlet? Arne Vajhøj <arne@vajhoej.dk> - 2011-11-01 22:09 -0400

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