<div dir="ltr">Sorry for the long delay in responding to this. When I run the models in the most recent version of SYMPHONY, they are both found to be infeasible in the presolve. If I turn off presolve, they are still both found infeasible. I checked this with another solver and got the same result. So I think your models are both infeasible. <div><br></div><div>This does not explain why you were getting different results with 5.6.1. There were some bugs fixed in the preprocessor in some later releases so I would first upgrade to the last release (5.6.11). Let me know if you have more issues.</div><div><br></div><div>Cheers,</div><div><br></div><div>Ted</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Apr 21, 2015 at 4:10 AM, Mikko Alinikula - SUBNIC OY <span dir="ltr"><<a href="mailto:subnic@kolumbus.fi" target="_blank">subnic@kolumbus.fi</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello Ted,<br>
<br>
We have succeeded in making a truss-optimization-system using SYMPHONY-code in MILP-calculations. Sometimes however SYMPHONY fails to find an optimum although it is there. SYMPHONY claims that there are no feasible solutions when called with "find_first_feasible"-parameter. I outputted .MPS-models of 2 cases :<br>
<br>
Attached is a .MPS-model, THERE_IS_NO_SOLUTION_FULL_MODEL.MPS, which is the original model. SYMPHONY returns = NO FEASIBLE SOLUTIONS.<br>
<br>
Attached is a .MPS-model with, THERE_IS_A_SOLUTION_REDUCED_MODEL.MPS, which is the original model with reduced number of integer-variables. For this SYMPHONY finds a optimum! This is the optimum that is included also in the original model!<br>
<br>
SYMPHONY-version is currently 5.6.1 and OS is WIN 32/64. I have linked statically SYMPHONY-libraries to my own code.<br>
<br>
Maybe some parameters for SYMPHONY needs to be adjusted? Or something ..<br>
<br>
BR<br>
<br>
Mikko Alinikula/SUBNIC Ltd./Finland<br>
<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Dr. Ted Ralphs<br>Professor, Lehigh University<br>(610) 628-1280<br>ted 'at' lehigh 'dot' edu<br><a href="http://coral.ie.lehigh.edu/~ted" target="_blank">coral.ie.lehigh.edu/~ted</a><br></div></div>
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