Infinite loop/stuck particle in voxelized phantoms with emstandard_opt4 and GATE v9.3

[cpommranz]

GATE/Geant4 enters an infinite loop when using the emstandard_opt4 physics list for voxelized phantoms. An infinite number of steps with step length 0 and dE 0 is produced (see tracking output below). Geant4 does not detect the stuck particle and does not try to force push it, as it typically does to unstuck particles.

Log output:

[...]

---

• G4Track Information: Particle = e-, Track ID = 3, Parent ID = 1

---

Step# X(mm) Y(mm) Z(mm) KinE(MeV) dE(MeV) StepLeng TrackLeng NextVolume ProcName
0 -9.69 2.08 -1.83 0.237 0 0 0 test_voxel_phys_Z initStep
1 -9.86 2.05 -1.8 0.229 0.00721 0.18 0.18 test_voxel_phys_Z msc
2 -10 2.03 -1.77 0.216 0.0133 0.142 0.322 test_voxel_phys_Z msc
3 -10 2.03 -1.77 0.216 3.5e-06 0.00128 0.323 test_voxel_phys_Z msc
4 -10 2.03 -1.77 0.216 8.8e-05 0.00336 0.326 test_voxel_phys_Z Transportation
5 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
6 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
7 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
8 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
9 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
10 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
11 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
12 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
13 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
14 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
15 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
16 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
17 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
18 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
19 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
20 -10 2.03 -1.77 0.216 0 0 0.326 test_voxel_phys_Z eIoni
[...]

• OS: Ubuntu 20.04
• Gate version: v9.3
• Geant4 version: v11.1.2
• Root version: v6-29-01
• Compiler version: gcc 9.3.0 (from the 9.3.0-1ubuntu2 deb package)
• Physics list: emstandard_opt4

The issue is gone when switching to the emstandard_opt3 physics list. I cannot reproduce this issue with GATE v9.1 and Geant4 v10.7.2, so it seems to be a recent regression.
I'm currently not sure if this issue is related to GATE or rather Geant4 itself. I will investigate further.
A minimal working example is available here: minimal_working_example.zip. Please be prepared to kill the process before running the example, as the vast amount of Hits produced in the infinite loop quickly eats up memory.

[NikEfth]

Hi @cpommranz. Your comment helped me a lot in my own situation.
I don't have voxelized phantoms, but I noticed the same behaviour starting, at least one year, ago. Probably, a bit more.
Using the _opt3 it works fine for me, too.
Have you find the source of this regression?

Kind Regards,
Nikos

[cpommranz]

Hi @NikEfth. I tested two more configurations:

• GATE v9.3 with Geant4 v11.1.3 (most up-to-date v11.1 patch release): Problem persists.
• GATE v9.3 with Geant4 v11.2.0: Works perfectly; cannot reproduce the issue.

So, this seems to be a regression in the Geant4 v11.1 series. Please note, that GATE v9.3 is only tested with the Geant4 v11.1 series. It compiles fine against Geant4 v11.2.0, but I haven't run the benchmarks.

[NikEfth]

Thank you.
I did as you said and installed geant 11.2 (for the tag v11.2) but unfortunately, the memory leak persists.
I think that it is much slower than previously, but I will need to run a full sim to know for sure.