Warnings with G4PathFinder::ReportMove()

Dear Geant4 users,

For a radioprotection simulation, I defined some concrete blocks (in magenta) and I used a scorer mesh in a parallel geometry (in grey).

However, during the simulation, I have a lot of warnings:

-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : GeomNav1002
issued by : G4PathFinder::ReportMove()
Endpoint moved between value returned by ComputeStep() and call to Locate().
Change of (End) Position / G4PathFinder::Locate is 1.00000036152755e-07 mm long
and its vector is (-9.922541721607558e-08,-1.114705128202331e-08,-5.483343556988984e-09) mm
Endpoint of ComputeStep() was (1117.800000099226,-230.9971355447562,2546.949761772873)
and current position to locate is (1117.8,-230.9971355559033,2546.94976176739)
*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------

I read the same message in an old post (http://hypernews.slac.stanford.edu/HyperNews/geant4/get/analysis/553.html) but I have no more information. Do you have an idea of the problem? How it impacts my results? I use version 10.4 of Geant.

Thank you in advance for your help.


The warning which you posted is for a very small change of position - 1e-7 mm. So I would not be concerned. Please look whether any of the moves reported are substantial - e.g. on the order of 0.1 mm or above if the volume you are simulating is on the order of a meter.

From the picture and your description it is not clear to me whether there is one scoring scoring mesh, and it is a simple box – or whether it is a more complex shape. Could you please clarify?

In other words: Does the geometry consists of one concrete block and a scoring volume which is a smaller box ? Or are there other volumes involved ?

If you can give some more information about the physics list which you are using, and the type of scoring mesh so that we can try to reproduce it in an example, it would be very helpful. Of course if it is possible for you to create a similar setup in one of our examples it would be ideal for identifying the source of the problem and fixing it.

Best regards,

Dear John,

Thanks for your reply. I looked over all the warnings, and I always have a move around 1e-7 mm.

I adapted the example RE03 to compute the neutron flux in a concrete block (1-meter square). I used a scoring mesh with the same size and smaller size, but I still have the problem.

I used FTFP_BERT and QGSP_BIC, and I have warnings for both. However, if I use QGSP_BIC_HP, everything is fine. Are the warnings related to the physic list? I put the mac file that I used as an attachment.

Best regards,


run1.txt (914 Bytes)

It’s not immediately clear why the problems would happen with one physics list but not another. There should only be indirect influence, if some types of particles have different spectra … or are even absorbed better in HP but propagate more in other physics list and find difficult spots …

I will try to reproduce the problem in the example, as soon as I have time.