Decision Optimization

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  • 1.  Time limit parameter

    Posted Thu October 06, 2022 04:18 PM
    Hello everyone.

    I have a question concerning the meaning of the parameter optimizer time limit in seconds, or CPXPARAM_TimeLimit (https://www.ibm.com/docs/en/icos/12.8.0.0?topic=parameters-optimizer-time-limit-in-seconds). My question is, does the time limit considers the time taken when the process is interrupted or preempted? For example, let's suppose I am:
    • Running a CPLEX model with CPXPARAM_TimeLimit of 600, i.e. 10 minutes of time limit;
    • Running several programs along with my CPLEX application; And
    • During the CPLEX execution, the Operating System decides to interrupt the CPLEX process, making it wait for 60 seconds, i.e. one minute.
    Will CPLEX consider this waiting time on its CPXPARAM_TimeLimit, i.e. CPLEX will make use of only 9 minutes on its optimization, or will CPLEX ignore the waiting time, and thus use the full 10 minutes in the optimization?

    Thanks and regards.

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    Matheus Andrade
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  • 2.  RE: Time limit parameter

    IBM Champion
    Posted Thu October 06, 2022 06:04 PM
    This is contingent on another parameter, CPXPARAM_ClockType. With the default setting (2), CPLEX uses "wall clock time", so it will terminate approximately 10 minutes after start regardless of how much (or little) time it was actively running. If the clock type is set to "CPU time" (1), it will terminate after approximately 10 minutes of actual CPU use.

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    Paul Rubin
    Professor Emeritus
    Michigan State University
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  • 3.  RE: Time limit parameter

    Posted Mon October 10, 2022 10:07 PM
    Thank you so much, this helps a lot.

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    Matheus Andrade
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