Robert Fourer
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Latest activity by Robert Fourer
Robert Fourer commented,
You are setting gurobi_options twice: option gurobi_options 'timelimit=100 outlev=1 mipgap=0 mipfocus=3';option gurobi_options 'logfile=C:\AMPL\2023_01_29\Replication01\logfile.temp'; The second s...

Robert Fourer commented,
That is a correct way to set the Gurobi time limit, and it's verified to be working with Gurobi 11.0 for AMPL. To be sure you are using it correctly, look for timelimit=7200 or lim:time=7200 in AMP...

Robert Fourer commented,
Hey bot! Couldn't you use Model.addGenConstrExp()?

Robert Fourer commented,
Does the setting of Gurobi parameter PreQLinearize make any difference in this situation?

Robert Fourer commented,
You can write a formulation such as the following in AMPL, and it will be accepted by the AMPLGurobi interface: subj to cons1 {i in 2..N+1}: x1[i]  x1[i1]  x2[i1] * x3[i1] * cos(x4[i1]) >=...

Robert Fourer commented,
The reset_initial_guesses setting works, but if it does not make a big difference, then you can conclude that the slower solves are likely not due to warm starts. Here are some additional checks th...

Robert Fourer commented,
I wouldn't expect that warmstarting would slow down Gurobi's solution process. But you can try turning off warmstarting by setting "option reset_initial_guesses 1;" in AMPL. It is possible that the...

Robert Fourer commented,
In J.A. Tomlin, "On Scaling Linear Programming Problems," Mathematical Programming Study 4 (1975) 146166, geometric mean scaling is defined as follows: Gurobi may be doing something of this sort....

Robert Fourer commented,
AMPL accepts this model without any errors. It is OK to write the objective as the sum of three variables, each of which equals a different expression. The expression for f2[i,j] has a product of 3...

Robert Fourer commented,
Set Gurobi's nonconvex option in your .run file. If you are already setting a gurobi_options string, then add nonconvex=2 to it. If you are not yet setting a gurobi_options string, then add this c...