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Changing the setting (aggregator & global thread limit)

  • 22 June 2019
  • 1 reply
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Hi,

There are some changes I did on the setting before I run my MIP project in AIMMS. I wish to know what they mean and how they work. Can anyone explain it to me?
1. I change the ‘aggregrator’ to 0.
2. I change the ‘global thread limit’ to 1.

Thank you in advance.
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Best answer by Marcel Hunting 24 June 2019, 18:01

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The meaning of the options can be found in the AIMMS Help. In the Option Tree, if you right-click on an option then the Help for that option will be opened.

The 'aggregator' option is a preprocessing option. This option, when set to a nonzero value, will invoke the CPLEX Aggregator to use substitution where possible to reduce the number of rows and columns before the active problem is solved. If the option is set to a positive value, then the aggregator will be applied the specified number of times, or until no more reductions are possible. At the default value of -1, the aggregator is applied once for LP, and an unlimited number of times for MIP. At this setting, all potential presolve reductions are performed for MIP. Possible values are:

-1: Default aggregation
0: None
n: n aggregations

The 'global thread limit' option specifies the maximal number of parallel threads that will be invoked by CPLEX. CPLEX can use parallel threads for solving MIP models and, if the barrier algorithm is used, for solving LP, QP and QCP models. The default value of this option is 0 in which case the number of threads used by CPLEX equals the number of (logical) cores in the computer.

Normally, the performance will be better if both options are at their default value.

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