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[diett004]

We are running high-RAM simulations (~1.5 TB) at the Minnesota Supercomputing Institute. The simulations tend to crash repeatedly, usually citing insufficient RAM. However, the same simulations do manage to complete intermittently. When they complete, HFSS consistently records a RAM value hundreds of GB below our actual allocation limit (1.97 TB). Our question: why would the simulations crash so often due to insufficient RAM when they don't end up requiring more than is available?

The only trend we notice is that higher frequency simulations (which usually require a finer mesh) tend to crash more frequently than lower frequency runs. However, as stated, when higher frequency simulations do successfully complete, they do not require much more RAM than lower frequency ones.

We tried using both the direct solver and the iterative solver to run our high RAM simulation. Switching to the iterative solver does save quite a bit of RAM (as much as 400 GB), however the same intermittent crashing problem still happens with somewhat finner meshes. It moves the bar up somewhat, but not enough. I have included the profile data from two different types of crashes. The first from before we switched to the iterative solver, and the second from after. Immediately below is the example of a crash using the direct solver. Note that it says "Out of RAM", but our actual ram limit was 1.97 TB, which is much higher than the 1.58 TB it lists using at the time of crashing. It is also important to remember that, as stated above, simulations like this intermittently succeed with significantly less RAM than our limit (1.3-1.5 TB).

The next image shows a crash that happened after switching to the iterative solver. The profile apparently shows no useful information:

[Praneeth]

Hi,

Thank you for reaching out to the Ansys learning forum.

This question looks like a duplicate to the original one - High RAM Simulations Usually Crashing, But Intermittently Succeeding. A reply is provided to your reply. Please post if you have any replies in that question itself. 

I will close this question for further replies and delete this question to remove duplicates from the forum. Kindly refrain from posting duplicate questions in the forum.

Best regards,
Praneeth.
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