Solver Error in EM-LF Simulation on Yoon-son Model

viniltc

Hi all,

I'm running a low-frequency neurostimulation simulation on Sim4Life Web using the Electro Ohmic Quasi-Static solver on the Yoon-son complete anatomical model.

Simulation settings:

Frequency: 1000 Hz
Electrodes: Two placed on the chest area

Boundary Conditions:
Flux boundary automatically applied to external bounding planes
Dirichlet boundary applied to both electrodes (set as “Treated as Port”)

The simulation took approx. 45 minutes to solve, but I encountered an error at the end. Here are the last lines of the log:

2025-05-30T11:23:35.790Z [INFO] [XCore.CLog] Iteration 4 and residual drop factor 5.33458e-06
2025-05-30T11:23:35.791Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":430,"type":"0","version":"0"}}}
2025-05-30T11:24:04.150Z [INFO] [XCore.CLog] Iteration 5 and residual drop factor 8.98461e-07
2025-05-30T11:24:04.152Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":500,"type":"0","version":"0"}}}
2025-05-30T11:24:32.557Z [INFO] [XCore.CLog] Iteration 6 and residual drop factor 4.14111e-07
2025-05-30T11:24:32.558Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":530,"type":"0","version":"0"}}}
2025-05-30T11:25:00.816Z [INFO] [XCore.CLog] Iteration 7 and residual drop factor 4.9417e-08
2025-05-30T11:25:00.818Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":600,"type":"0","version":"0"}}}
2025-05-30T11:25:29.127Z [INFO] [XCore.CLog] Iteration 8 and residual drop factor 1.48857e-08
2025-05-30T11:25:29.128Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":650,"type":"0","version":"0"}}}
2025-05-30T11:25:57.655Z [INFO] [XCore.CLog] Iteration 9 and residual drop factor 2.25318e-09
2025-05-30T11:25:57.657Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":720,"type":"0","version":"0"}}}
2025-05-30T11:26:25.941Z [INFO] [XCore.CLog] Iteration 10 and residual drop factor 2.95529e-10
2025-05-30T11:26:25.942Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":790,"type":"0","version":"0"}}}
2025-05-30T11:26:54.268Z [INFO] [XCore.CLog] Iteration 11 and residual drop factor 6.34014e-11
2025-05-30T11:26:54.270Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":840,"type":"0","version":"0"}}}
2025-05-30T11:27:22.560Z [INFO] [XCore.CLog] Iteration 12 and residual drop factor 1.48467e-11
2025-05-30T11:27:22.562Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":900,"type":"0","version":"0"}}}
2025-05-30T11:27:50.924Z [INFO] [XCore.CLog] Iteration 13 and residual drop factor 1.8532e-12
2025-05-30T11:27:50.926Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":970,"type":"0","version":"0"}}}
2025-05-30T11:28:19.032Z [INFO] [XCore.CLog] Iteration 14 and residual drop factor 3.03701e-13
2025-05-30T11:28:19.035Z [INFO] [XCore.CLog] JSON PROGRESS : [Info]  {{{"descriptor":"Solving linear system: Real Part","permill_completed":1000,"type":"0","version":"0"}}}
2025-05-30T11:28:19.037Z [INFO] [XCore.CLog] Elapsed time for 'Solving linear system: Real Part' was 00:07:06 wall clock time.
2025-05-30T11:28:19.039Z [INFO] [XCore.CLog] Solved linear system: Current and peak CPU memory usage:  42.5 GB /  42.5 GB (current is 100.0 % of peak)
2025-05-30T11:28:19.041Z [INFO] [XCore.CLog] Solver returns: 'converged (relative tolerance)'.
2025-05-30T11:28:21.522Z [ERROR] [XCore.CLog]  
2025-05-30T11:28:21.524Z [ERROR] [XCore.CLog] The solver process failed to exit correctly: eExitFail

The solver fails to exit cleanly. During the run, I observed CPU memory usage jumping from about 40% to 100% at times. Could this indicate that memory limitations caused the eExitFail error?

Has anyone seen a similar issue with large anatomical models? Any suggestions on how to debug or avoid this error?

Thanks in advance

carbonell

Hello,

Which version of Sim4Life Web are you using? Lite? IO? Science? What are your grid and solver settings?

This issue could be indeed related to memory, however to have a better understanding of the problem I would suggest to contact the support team directly and share the project with us (s4l-support@zmt.swiss).

viniltc

Hi, thanks for your response.
I'm using Sim4Life IO and quite novice user. If the issue is memory-related, could you please advise on the recommended resource settings? Specifically, I’d like to know which Tier category the project should be configured under for simulations involving the full anatomical model and the entire body region.
Also, are there any best practices or suggestions for optimizing memory usage in this context?

Thanks again.

carbonell

Hi,

Did you run your simulation using our SMALL server (16 CPU cores, 32 GB RAM) or the LARGE server (48 CPU cores, 96 GB RAM)?
Also, could you let us know the total number of cells in your simulation?

As a general suggestion for optimizing memory usage, you can start by running a simulation with a coarse grid to identify regions where the fields are negligible. Based on this, you can adjust the grid padding settings to exclude those body regions from the simulation domain, effectively "cropping" unnecessary areas and reducing the computational load.

ZMT zurich med tech

Solver Error in EM-LF Simulation on Yoon-son Model