CPLEX presolve would not turn off

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darali00
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CPLEX presolve would not turn off

Post by darali00 »

Hello everyone,

I use CPLEX to solve a QCP model. After trial and error on previous version of my model, I figured turning off presolve reduces my run time by around 2/3 (2 hours instead of 6 hours). This is the option file setting in my code:
$onecho > cplex.opt
names no
scaind 1
preind 0
$offecho
It was working and presolve was turned off. It has stopped working since I have changed the model a bit, even though the same opt file is being used!

In my last adjustment of the model, I changed one equation by setting a condition on what should be included. Original code:
LIM_Stormax(t,wn).. Stor(t,wn)=L= stor_max(wn);
Current code:
LIM_Stormax(t,wn)$(not exc_low(wn)).. Stor(t,wn)=L= stor_max(wn);

Now, after "Starting Cplex" I still see "CPXPARAM_Preprocessing_Presolve 0" which should mean presolve is turned off, but presolve runs (I see "Presolve has eliminated 29880664 rows and 30310466 columns..."). Why is presolve running even though I get the message "CPXPARAM_Preprocessing_Presolve 0"? How should I prevent presolve from running?

I would be happy to share more details, if needed.
Thanks a lot in advance.
Bests,
Ali
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dirkse
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Location: Fairfax, VA

Re: CPLEX presolve would not turn off

Post by dirkse »

Ali,

Interesting question. If you attach the entire .log file from your run to a post that will allow people to search for clues to explain this behavior.

-Steve
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