Learning Forum

[utkarsh.patel]

Hello,

I am running Modal Analysis at using 4 Cores. After first run I got an error.

After this I changed number of cores to 7 from 4 and restarted analysis just so I can use more Ram and CPU for faster results.

I got restart analysis error.

Anyone, please help. thanks. 

[peteroznewman]

Don't restart with a different number of cores.  If you want to change the number of cores, Clear Generated Data and start the Solve from the beginning.

Also, if you link a downstream analysis such as Random Vibration or Harmonic Response, you must not change the number of cores.

[utkarsh.patel]

Hello Peter,

Understood on why I was seeing the same error even after clearing generated data. Because I had a static structural analysis linked to it which ran on 4 cores and I had not cleared generated data on there to run it again on 7 cores so that eventually i can run Modal on 7 cores as well.

Can I please ask another question, would you be able to tell me what would be the difference between using commands like BCSOption or DCSoption with Incore and outcore. 

I am trying to run my models just so It can utilize max number of RAM and CPU so that my results are back to me faster rather than having it run for 2-3 hours.

[peteroznewman]

The Solve Process setting should have the Distributed box checked as that usually runs faster than having it unchecked.  With that checked, you would use the DSCoption to make further adjustments, though that is rarely needed.  The solver will automatically calculate whether it can run incore or not, though there is some conservatism in the estimate. If your model is just on the edge and chooses to run out-of-core, you can force it to try to run incore using the DSCoption and if you are lucky, it may successfully run incore, though it will automatically switch if it can't be done.  You can also try to reduce the number of nodes until the model will run incore. I have never wanted to force the solver to run out-of-core, I don't see why I would ever want to.

The difference between incore and out-of-core is larger if you are using a slow HDD for storage.  If you have a fast SSD, there is less difference betwen incore and out-of-core.

Another tool to minimize the total wait time is to carefully select the time steps and substeps.  If the time steps are too large or substeps too few, time will be wasted if the solver has to do a bisection or just needs a lot of iterations to converge on a substep. You can also waste time if you request a large number of substeps that you may not need.

[utkarsh.patel]

Understood. Thanks Peter. Your responses to all the questions asked by alot of people on this platform are very informative and helpful.

Thanks.