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 APS or IRUN multithread = multicore? 

Last post Wed, Oct 17 2012 7:26 AM by Andrew Beckett. 5 replies.
Started by greatqs 17 Oct 2012 06:39 AM. Topic has 5 replies and 1319 views
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  • Wed, Oct 17 2012 6:39 AM

    • greatqs
    • Top 500 Contributor
    • Joined on Tue, Feb 15 2011
    • Posts 26
    • Points 460
    APS or IRUN multithread = multicore? Reply

    Is the terminology of "multithread" (i.e. +mt = x) in APS/IRUN means number of CPU core to use? On a 12 cpu core machines, the max number of "multithread" should be 12, is it right? Thanks

     

     

    • Post Points: 20
  • Wed, Oct 17 2012 6:52 AM

    Re: APS or IRUN multithread = multicore? Reply

    Yes, that's right. The tool won't allow you to use more threads than "cores" that are available. Note that I put "cores" in quotation marks because if you have hyperthreading enabled, that will increase the number available to use - although in general we don't recommend using hyperthreading with APS because you don't typically get good scaling with a heavily floating point application like APS.

    Regards,

    Andrew.

     

    • Post Points: 20
  • Wed, Oct 17 2012 7:00 AM

    • greatqs
    • Top 500 Contributor
    • Joined on Tue, Feb 15 2011
    • Posts 26
    • Points 460
    Re: APS or IRUN multithread = multicore? Reply

    Andrew,

     Thanks!

     Is "hyperthreading" a simulator option or machine setup?

     How about AMS simulation using IRUN? Since "+mt=x" is APS arguments, if the simulator need also to resolve HDL events, will it need more cores than specified by "+mt=x"? I'm asking this is to correct setup the LSF strings "bsub -n y" to correlate irun +mt=x arguments, otherwise LSF may confuse and causes the farm to be low efficient. 

    Regards,
    QS
     
    • Post Points: 20
  • Wed, Oct 17 2012 7:14 AM

    Re: APS or IRUN multithread = multicore? Reply

    Hyperthreading is a capability of Intel processors, and it is enabled/disabled as a BIOS setting usually. So it's a machine setup thing.

    If you've allocated a certain number of cores when you submitted the job with LSF, you can use +mt=lsf - and then it will inherit the number of threads from the LSF settings.

    There's no need to allocate more threads for HDL aspects - it's only the analog solver that is multi-threaded (that includes any analog parts of HDLs too).

    Regards,

    Andrew.

    • Post Points: 20
  • Wed, Oct 17 2012 7:20 AM

    • greatqs
    • Top 500 Contributor
    • Joined on Tue, Feb 15 2011
    • Posts 26
    • Points 460
    Re: APS or IRUN multithread = multicore? Reply

    Andrew,

    For example 4 cores are used by analog solver for multithreading, but digital solver still need extra core for digital HDL, right? Otherwise 4 threads of the analog solver may not be balanced.

     

    Thanks,

    QS

    • Post Points: 20
  • Wed, Oct 17 2012 7:26 AM

    Re: APS or IRUN multithread = multicore? Reply

    No, you don't need to do that. The +mt argument is only used for APS anyway - and the digital HDL is not multi-threaded so will be handled in the "main" thread. Given that the analog solver and digital "solver" are not active at the same time, there's no real benefit in having the digital in a separate thread from the analog (there has to be synchronization between the analog and digital - this is a consequence of how the two worlds are aligned).

    Regards,

    Andrew.

    • Post Points: 5
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Started by greatqs at 17 Oct 2012 06:39 AM. Topic has 5 replies.