Question about servo wall?

Submitted by Sherif on Fri, 08/20/2021 - 15:25

I'm trying to make a triaxial compression test in two scripts. First, generating particles using insert/stream in a cubic region then unfix all walls and save a restart file. Second, fix new servo walls and apply equal pressure from all walls except the base wall and after reaching the target confining pressure, I only increase the pressure of the upper wall to apply vertical compression on the sample. I use kp = 1, ki = 0, kd = 1e-6.

My problem is that some steps takes too much time especially the compression steps. Here is the output timings:

Pair time (%) = 355.977 (34.389)
Neigh time (%) = 0 (0)
Comm time (%) = 0.604068 (0.0583555)
Outpt time (%) = 0.909893 (0.0878996)
Modfy time (%) = 677.478 (65.4473)
Other time (%) = 0.181394 (0.0175235)

It is obvious that "Modfy time (%)" is consuming much time and I found that this time is mainly consumed on a certain fix:

Fix xwall_min_servo mesh/surface/stress/servo time (%) = 666.978 (64.4329)
Fix xwall_max_servo mesh/surface/stress/servo time (%) = 0.111867 (0.0108068)
Fix ywall_min_servo mesh/surface/stress/servo time (%) = 0.108422 (0.010474)
Fix ywall_max_servo mesh/surface/stress/servo time (%) = 0.10341 (0.00998987)
Fix zwall_min_servo mesh/surface/stress/servo time (%) = 0.0728636 (0.00703894)
Fix zwall_max_servo mesh/surface/stress/servo time (%) = 0.098178 (0.00948442)

So my question is why this certain wall "xwall_min" is taking that much time and how to fix this issue?

Thanks in advance