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Re: lp.cc (octave-forge) problem


From: Ben Sapp
Subject: Re: lp.cc (octave-forge) problem
Date: Wed, 12 Jun 2002 09:55:27 -0500

Hi,  

I can not duplicate your results on a Linux machine.  However, the problem 
seems to be worse on a Linux machine.  It causes a segfault in Octave.  
Clearly, this program is not operating as intended.   I must admit that a 
couple of weeks ago I noticed a similar problem with lp on a different 
problem.   Currently I have many print statements in my version of lp to try 
help diagnose the problem.   I still do not know what is going wrong.  

Thank you for another example problem.  Maybe this will help me find the 
problem(s) with lp.

On Tuesday 11 June 2002 05:43 pm, A S Hodel wrote:
> I've just started trying Ben Sapp's lp.cc code (from octave-forge) on
> Mac OS X, and I'm getting some strange results.  Before I dig too
> deeply, I'd like to see if these results occur on other platforms as
> well or if this is unique to the (currently experimental) .oct file work
> on Mac OS X.
>
> Here's the m-file I use to test lp:  all solutions should lie within the
> range [-10,10], with the number of equality constraints increasing from
> 0 to two as the iteration goes.  The results on my machine are at the
> end.  Notice that the upper bound is violated and that the equality
> constraints are not enforced.
>
> If someone would run this script and let me know if my results are
> duplicated, I'd appreciate it.  If they are, then I'll debug the lp.cc
> code itself.  If not, then I've got something else going on that I'll
> have to figure out.
>
> Thanks.
>
> A. S. Hodel
>
> MyLpTest.m
> ============
> A = eye(2,6);
> c = [1 -2 3 -4 5 -6]';
> b = [1;1];
> lowerBound = -10*ones(size(c));
> upperBound = 10*ones(size(c));
>
> for nEqConstr = 0:2
>     printf("\n\nnEqConstr=%d\n",nEqConstr);
>     # compute results
>     x = lp(c',A,b,lowerBound,upperBound,nEqConstr);
>
>     # check against equality constraints, lower and upper bounds
>     mesg = str2mat("low","  ","high");
>     for ii=1:length(x)
>       istr = 2 - (x(ii) < lowerBound(ii)) + (x(ii) > upperBound(ii));
>       printf("%4d: %12.4g %12.4g %12.4g %s\n", ii, lowerBound(ii),
> x(ii), ...
>         upperBound(ii), mesg(istr,:));
>     endfor
>     ConstraintCheck = A*x - b
> end
>
> ========= Output of the program: =========
>
>
> nEqConstr=0
>      1:          -10           10           10
>      2:          -10           21           10 high
>      3:          -10           10           10
>      4:          -10           30           10 high
>      5:          -10           10           10
>      6:          -10           30           10 high
> ConstraintCheck =
>
>      9
>     20
>
>
>
> nEqConstr=1
>      1:          -10           10           10
>      2:          -10           21           10 high
>      3:          -10           10           10
>      4:          -10           30           10 high
>      5:          -10           10           10
>      6:          -10           30           10 high
> ConstraintCheck =
>
>      9
>     20
>
>
>
> nEqConstr=2
>      1:          -10           21           10 high
>      2:          -10           21           10 high
>      3:          -10           10           10
>      4:          -10           30           10 high
>      5:          -10           10           10
>      6:          -10           30           10 high
> ConstraintCheck =
>
>     20
>     20
>
>
>
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
>
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
> -------------------------------------------------------------

-- 
Ben Sapp                         Los Alamos National Laboratory
email: <mailto:address@hidden>   Phone: (505)667-3277
Fax:   (505)665-7920             URL:   http://www.neutrino.lanl.gov/
--



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Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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