Chris,

You can access certain model information with . in GAMS, e.g., .resusd will show you the time used by the solver. You can for example display this information or create a parameter consisting of different attributes and use GDXXRW to write the information to Excel. The gap cannot be accessed directly but it can be calculated. The following is an example I added to the end of the model dice from the GAMS model library:

stats(‘Time Used’) := xdice.resusd;

stats(‘Absolute Gap’) := abs(xdice.objest - xdice.objval);

stats(‘Relative Gap’) := abs(xdice.objest - xdice.objval)/abs(xdice.objest);

Note that some solvers (like Cplex) use a different definition of the relative gap. This can be seen here:

stats(‘Relative Gap (Cplex)’) := abs(xdice.objest - xdice.objval)/(1e-10+abs(xdice.objval));

Information about the absolute and relative gap can also be found at the GAMS Support Wiki:

http://support.gams-software.com/doku.php?id=solver:what_is_optca_optcr

I hope that helps,

Lutz

Bodenstein wrote:

Dear Gamsworld,

For a current model, I would like to do a parametric analysis of the

model (thanks for the looping gams trick btw.) for more than 2.5k

runs. Writing the solution to Excel is doing fine. I am however

unable to write the runtimes, or information about the relative gap to

theoretic optimum to file aswell.

Is there a way to write the solver runtime, and gap information to a

variable, or perhaps a way to directly export the information, so that

It’s “automatically” (with GDXXRW) written to the Excel file along

with the solutions. Or perhaps could you link me the manual which

covers these topics?

Regards

Chris

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Lutz Westermann LWestermann@gams.com

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