From: Nuralanur@...
Date: 2006-05-07T05:58:44+09:00
Subject: Numerical Ruby - Segmentation faults, GSL trouble

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Dear all,
 
I have to determine the minima of a multiparameter  mathematical function 
numerically.
I try to use the simplex method, as implemented in Ruby-Gsl, to do  this.
 
Below is some code from an example as given in the documentation of  Ruby/Gsl.
However, when I run this on Cygwin (Windows XP), I get a segmentation  fault
from the line where the parameters are set, whereas in Fedora, I am not  
allowed
to allocate even the function to minimize.
 
Has anybody had this problem before ? Has anybody some self-written  code
for multidimensional minimization (preferably simplex method)?
 
Thank you very much in advance,
 
Best regards
 
Axel 
 
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#!/usr/bin/env ruby

require("gsl")

include GSL::MultiMin



np = 2



my_f = Proc.new { |v, params|

  x = v[0]; y = v[1]

  p0 = params[0]; p1 = params[1]

  10.0*(x - p0)*(x - p0) + 20.0*(y - p1)*(y - p1) + 30.0

}



my_func = Function.alloc(my_f, np)    # ERROR in Fedora: undefined method 
`alloc' for GSL::MultiMin::FMinimizer:Class (NoMethodError)


my_func.set_params([1.0, 2.0])      # parameters: SEGMENTATION fault in 
Fedora.

x = Vector.alloc([5, 7])

ss = Vector.alloc(np)

ss.set_all(1.0)



minimizer = FMinimizer.alloc("nmsimplex", np)

minimizer.set(my_func, x, ss)



iter = 0

begin

  iter += 1

  status = minimizer.iterate()

  status = minimizer.test_size(1e-2)

  if status == GSL::SUCCESS

    puts("converged to minimum at")

  end

  x = minimizer.x

  printf("%5d ", iter);

  for i in 0...np do

    printf("%10.3e ", x[i])

  end

  printf("f() = %7.3f size = %.3f\n", minimizer.fval, minimizer.size);

end while status == GSL::CONTINUE and iter < 100


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