[Coin-discuss] Inconsistency between Osi Solves

[Ashutosh Mahajan]

hi Pedro,
i just tried the same experiment by reading some integer programming instances
from mps files and using
OsiClpSolverInterface and OsiSymSolverInterface. both seem to give
consistent solutions. what version of symphony are you using?
could you just dump the mps file using si->writeMps() and mail it to me?
also did you set a timelimit or node limit or any other parameters?
thanks.

--
regards
Ashutosh Mahajan
http://www.lehigh.edu/~asm4

> From: Pedro Teixeira <pedro.t at gmail.com>
> Date: Feb 6, 2008 2:55 PM
> 
> 
> Hi,
> 
> I am new to coin-or and not sure if this is the appropriate list to
> post. I'm getting very different solutions when using the same model
> but switching from OsiClpSolverInterface and OsiSymSolverInterface.
> 
> my current usage is simple:
> 
> si->loadFromCoinModel(model , true);
> si->initialSolve();
> si->branchAndBound();
> 
> With ClpSolver, it takes much more time and I get (for illustration):
> Search took 43600 iterations and 7302 nodes
> Clp0000I Optimal - objective value 115
> 
> However, with SymSolver I get the result instantaneously:
> Solution Found: Node 1, Level 1
> Solution Cost: 10.000
> 
> Shouldn't I get the same results? Or is there any known issues with Osi?
> Can anyone shed in any light?
> 
> cheers,
> Pedro