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AMS simulator with APS and multi-thread

SteveRFIC

I am using the AMS simulator to run AMS sims.

In the "setup-high performance" menu, I choose APS. I enable ++aps and in the multi-threading part I choose auto.

Now I have a 4-core, 8-thread CPU and I am running simulation locally on my machine. 

I expect the simulator to use all the cpus for simulation. When I look at the sim log file, it says

"Multithreading Enabled: 8 threads in the system with 8 available processors."

However, I also monitored the CPU usage during the simulation, and it only uses 140% cpu, instead of 600-800%.

I also manually chose to use 4, or 8 threads (second screenshot below). It still just uses 140% cpu and the simulation time is the same.

The simulation takes one hour, I wonder why the simulator does not use all of the cpu to speed up the simulation.

How does it choose how many cores to use? what can I do to make it use the full capacity of the cpu?

Also, I noticed that if I set the multi-thread option to auto, then the simulator always use 8 threads, no matter how many cores I have. Is this true? WIll the simulator dynamically adjust the core/thread to use if I run it on different machines with different cpus?

Thanks!

Parents
  • SteveRFIC

    I read the following from some previous posts (community.cadence.com/.../22220)

    +multithread=N Turns on multithread capability. N is the specified number of threads. For baseline mode, at most 4 threads are allowed. For Turbo mode, at most 8 threads are allowed. You may use `+mt' as an abbreviation of `+multithread'

    Is this true? There is a limit of max 8 threads? This seems to be agreeing with what I've seen. I tried to run the sim on a 16core/32thread cpu, it still says 8 threads in the system with 32 available processors.

    So my question is two fold:

    1. how many threads can be used (maximum)?

    2. even with 4 ot 8 threads, why the cpu usage is only 140% instead of 400% or 800%

    This is confusing :(

Reply
  • SteveRFIC

    I read the following from some previous posts (community.cadence.com/.../22220)

    +multithread=N Turns on multithread capability. N is the specified number of threads. For baseline mode, at most 4 threads are allowed. For Turbo mode, at most 8 threads are allowed. You may use `+mt' as an abbreviation of `+multithread'

    Is this true? There is a limit of max 8 threads? This seems to be agreeing with what I've seen. I tried to run the sim on a 16core/32thread cpu, it still says 8 threads in the system with 32 available processors.

    So my question is two fold:

    1. how many threads can be used (maximum)?

    2. even with 4 ot 8 threads, why the cpu usage is only 140% instead of 400% or 800%

    This is confusing :(

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