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### Unknown option (mipstart=1)

Posted: Wed Jul 26, 2017 9:58 pm
Hey guys, I have a problem with GAMS and want you to help me (PLS).
I have developed a two step algorithm, in which a heuristic algorithm creates a relatively high quality and feasible solution at the first step, then a MIP-based algorithm (or partial MIP algorithm) improves the solution found at the first step. For more clarification, an incumbent solution is created at the first (as we have created it at the first step); afterward, it fixes some of the main decision variables and unfixes the rest of them. To develop such a two step algorithm, I have linked GAMS and MATLAB with each other. So far, I do not have any problem with the developed algorithm. Even more, the simple GAMS file of the proposed model does not have any problem.

To increase the speed of this two step algorithm, I tried to set the initial values of unfixed decision variables (originated from the incumbent solution). To do so, I used ' .l ' to set the intended initial values; furthermore, I used ' mipstrat ' option and set it equal to 1. But I confronted with an error that I am not totally aware the reason behind it. The error is illustrated in the following link:

https://ibb.co/chVKAQ

I was just wondering to know what would be the reason behind this error. In advance, I want to appreciate your sincere assistant.

BTW, I have written the following options for the GAMS file:

Option MIP=Cplex, limrow=1, limcol=1;
Option optca=0, optcr=0;
Option Reslim=120;
Option Iterlim=10000;
Option mipstart=1;

starttime=jnow;
Solve Finall using MIP minimizing f;

Regards,
A. Moosavi

### Re: Unknown option (mipstart=1)

Posted: Thu Jul 27, 2017 7:41 am
Hi,

mipstart is not a GAMS but a solver option, see e.g. the CPLEX solver manual: https://www.gams.com/latest/docs/solver ... EXmipstart
Hence, mipstart needs to be set in a solver option file: https://www.gams.com/latest/docs/solver ... PTION_FILE

I hope this helps!

Best,
Fred

### Re: Unknown option (mipstart=1)

Posted: Fri Jul 28, 2017 9:55 pm
Fred wrote:Hi,

mipstart is not a GAMS but a solver option, see e.g. the CPLEX solver manual: https://www.gams.com/latest/docs/solver ... EXmipstart
Hence, mipstart needs to be set in a solver option file: https://www.gams.com/latest/docs/solver ... PTION_FILE

I hope this helps!

Best,
Fred
I've got express my appreciation for you worthwhile help.