slow mechanism simulation

[kparssinen]

Some people here have reported that mechanism simulation run extremely slow. I had the same problem. I made a 8 wheel machine model, tires modelled as bushings and run a dynamic analysis with no movement. It took more than on hour to solve, but used only 3% of processor capacity (HP Z840, 16cores, 64Gb RAM).

I changed these settings and managed to reduce the solve time in to seconds.

1) mdo_integration_method = explicit (was automatic)

2) sim_solver_memory_allocation = 16384 (was 512)

3) mechanism_significant_digits = 16 (was 12)

I assume some or all of these have solved the problem, I also changed these:

4) cpus_to_use 16 (was 😎

5) transparency no (was yes)

Other experiencing similar promlems migth also try these, but still first thing to sort out is the model itself. There may be for instance typing errors in input values or incorrect units etc.

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[JonathanHodgson]

3% CPU on 16 cores (I assume this is 8 physical cores with hyperthreading?) suggests there's another bottleneck (1 core should be 6%).  If you open Resource Manager (from the Performance tab in Task Manager), do you see significant disk (or network) access?

[kparssinen]

Yes 8 physical cores. Creo had no disk activity, but there is network activity.

[ChrisKaswer]

MDO is not able to take advantage of multiple cores. MDO is also not influenced by the "sim_solver_memory_allocation" setting - these are both for Simulate. If you shut off the setting for updating the display during solve you will get it to complete much faster. Also try replacing the bushings with pin joints - these will run much faster.

[JonathanHodgson]

Christopher Kaswer wrote:

... If you shut off the setting for updating the display during solve you will get it to complete much faster.

Ah, that's almost certainly it!

[kparssinen]

Setting display update off was the first thing to try, no effect. Also, I agree that sim_solver_memory_allocation and cpus_to_use should not be effective, but had to try because you never know for sure if some setting has been re used.