Originally posted by: SystemAdmin

[namsu said:]

Dear,

I've coded a LP model using a concert in c++.
the strange thing is, when I check the running time as belows:

IloTimer timerS(env);
timerS.start();
cplexS.solve();
cout << "CPU time: " << timerS.getTime() << " sec., status: " << cplexS.getStatus() << endl; <br />
it took 0.75 seconds.
However, after I export the lp model using cplexS.exportModel("slave.lp"),
in interactive optimizer, I read the model, and solve the same model using "opt" command.
Then, it took only 0.01 seconds.
Is this possible? 75 times faster than concert!!
anyone can help to understand this situation?

thanks in advance.
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[prubin said:]

First, if you repeat the experiment do you still see the same time disparity?  Run times can be a bit random.

Second, you didn't indicate your platform.  I believe that IloTimer objects use CPU time on Linux/Unix systems but wall-clock time on Windows.  So if this was on Windows, part of the 0.75 seconds could have been Windows pausing your job while something else ran in the background.

Third, you might try moving the exported file to a different directory and running the interactive optimizer there.  CPLEX has advanced starts turned on by default, so the interactive run might have benefited from finding the optimal basis from the previous run lying around.

/Paul
#CPLEXOptimizers
#DecisionOptimization