Clarification on error/warning messages

Running and Runtime Errors
1

Versions

FLUKA: 4-5.0
Flair: 3.4-0
Operating system: WSL Ubuntu

Description

Dear FLUKA experts,

I have a question regarding the error files I obtain from my simulations. All simulations finish successfully (i.e., they do not stop due to critical issues), but I receive a number of warnings and error messages. I would like to understand the meaning of these messages and whether I need to take any action to avoid them.

I have read in the manual that some messages (e.g., “*** Umfnst” or “COUSET, TXYZ”) are simply debugging outputs and can be ignored. However, I could not find clear explanations for the following messages:

ID1:
Warning: Too many failed attemps to perfom (n,Ag)
on Z= 14 A= 28 Ekin= 8.4234336583434155E-003

ID2:
Warning: Too many failed attemps to perfom (n,Pg)
on Z= 14 A= 28 Ekin= 7.9842106901292995E-003

ID3:
Warning: Too many failed attemps to perfom (n,NNg)
on Z= 1 A= 2 Ekin= 4.4633653145609298E-003

ID4:
Warning: S(a,b) negative iso-probable interval found it=7 xp=0.999831 xi=0.999817

ID5:
Evevap_fis: failure in energy conservation!! 0.0000000000000000 12.113997428696649

ID6:
*** PWNINE Problem in axestr, restart..
NP= 1 UMO= 13.992018162230767 AXESTR= 13.992024016295980
PART=Ng

ID7:
Error: Too many tries for an neutron inelastic reaction

Additional messages appear when simulating 4He or 12C ions:

ID8:
*** Frmbrk: we are dealing with a bag of 7 62.701 identical nucleons, go on folks! ***

ID9:
*** Umfadj_sng: Umo, Amcms(1)+Amcms(nttprt), Amcms(1) 4.6862445601916090 4.7864123858214889 0.93827231000000000 ***

ID10:
*** Frmbrk: unable to break up an unstable nucleus! 15 10 0 14008.7 40.0878 ***
*** Evprtn: unstable nucleus out of the Fermi Break up 15 10 -1

Could you please clarify whether these messages indicate real problems or if they can be safely ignored?

Thank you in advance for your help! Best,
Stefan

Input files

Error file for proton simulation:
20250814_c_r05_01001.err (4.3 MB)

Error file for helium simulation:
20250811_c_r07_01001.err (3.8 MB)

Input file:
20250814_c_r05_01.inp (28.5 KB)

4

Hi @stefan

indeed all of the above warnings are corner cases that typically are due to floating point precision errors and unlucky random sampling which fails to close the kinematics of the interaction by a tiny amount. The event is either resampled or is accepted as is. The net effect in the simulation is negligible.

For instance:

ID1,2,3 points to inconsistency on neutron data e.g. the cross section shows that the channel is open at a certain energy (threshold reaction), however the final states in the data open at a slightly higher energy.

ID4 NJOY processing problem, producing an energy interval where Ehigh < Elow (due to numerical precision). This interval is ignored.

As hinted above, all of these can be safely ignored.

5

Dear Vasilis,

Thank you very much for taking the time to explain these warning and error messages.

Best regards,
Stefan