Re: [eclipse-clp-users] LP solvers via eplex

 luke2k4_at_gmail.com wrote:
> 
> Dear ECLiPSe users,
> I wanted to ask you about your experience with interfacing LP solvers
> through the eplex lib.
> I have been recently working on linear relaxation of a large industrial
> problem ( more than half a million variables and and several tenths of
> thousands of constraints), and I've cosen the ECLiPSe environment to
> model the problem because it's good for fast prototyping. I've used the
> Coin-OR CLP solver which is default in ECLiPSe. However I'd like to make
> some performance tests with other solvers such as GLPK.

CLP is generally considered better than GLPK, see benchmarks at
http://plato.asu.edu/ftp/lpfree.html


> Sticking to the GLPK for a moment, if I understand it correctly, I would
> have to build the GLPK with the Coin-OR OSI libraries added, to get a
> dll which could  then be loaded by eplex ? I've seen that there is
> already an entry in the eplex_lic_info.ecl for glpk, so provided that I
> have a glpk library with osi I would have to uncomment the line, create
> a module "eplex_osi_glpk.ecl" just like for the other solvers and than
> load ":- lib(eplex_osi_glpk)" instead of ":- lib(eplex_osi_clpcbc)",
> please correct me if I am wrong at some point.

I leave that to Kish to answer.


> Now moving to Express-MP, as far as I know this is commercial software
> from "dash optimization", so I won't be able to use that with eplex
> unless I have a valid license (the same case with CPLEX).

You can now get a free academic licence for Cplex.  Not sure about
Xpress (now fico.com).  I have tested eplex a few months ago with
Cplex 12 and Xpress 20.


> What are than
> the libraries in the \lib\ARCH\express1525 for ? At first I thought
> these are the complete LP solver libraries because they are quite big,
> too big to contain only the interface.

They are from the time when we had an agreement with Dash optimization
allowing us to distribute their solver freely to academics.


> One more thing, when I run the Coin-OR CLP via eplex I get quite high
> memory consumption ( up to 1GB ) which is understandable because the
> problem is large. My question is does ECLiPSe limit in any way the
> memory usage of the external solvers ? I would not like ECLiPSe to do
> that.

No, Eclipse doesn't limit solver memory other than by sharing the
same process and address space.


> I got the global stack overflow a few times but i suppose that was
> because of large data structures created while building the problem
> definition for the external solver in eplex and not because of the
> Coin-OR CLP memory usage (no problems after increasing the global stack
> to 0.7GB).

Yes, that would be expected.


-- Joachim