Support #25394

Build Art with CLHEP

Added by Julia Yarba about 2 months ago. Updated about 23 hours ago.

Target version:
Start date:
Due date:
% Done:


Estimated time:
SSI Package:


Now that Geant4 version 10.7 (latests public release) requires CLHEP would it be possible to build Art with this version of CLHEP ?


#1 Updated by Lynn Garren about 2 months ago

Julia, are you able to build 10.7 with the older CLHEP? Please help us understand the urgency of this request.

#2 Updated by Julia Yarba about 2 months ago

Hello Lynn, all,
Yes, I'm able to build Geant4 10.7 with CLHEP although it requires a (local) patch.
However, CLHEP features updates to a number of physics constants, thus it's likely to be of interest to the users community.
Here is from the change log: ==============================
09.11.20 Release CLHEP- ==============================

14 July 2020 - K.Savvidis, G.Cosmo

  • Random: Use 32-bit internal seeds types coherently in MixMaxRng.
    Addressing CLHEP JIRA ticket #156.

2020-07-20 Gabriele Cosmo <>

#3 Updated by Krzysztof Genser about 2 months ago

Please note that the CLHEP JIRA ticket #156 addressed a segfault in the MixMax engine when setting seeds using more than 2 of its elements
and that may impact experiments using this engine once a need to use all four seed elements comes up.

#4 Updated by Lynn Garren about 2 months ago

Thank you for the information. I note that a couple more small fixes have recently gone into CLHEP. There will likely be a release soon, which should also be suitable.

#5 Updated by Lynn Garren about 1 month ago

LArSoft is currently using geant4 v4_10_6_p01. NOvA is, I believe, using v4_10_4_p02d. We need to ensure that it is possible to build these older releases of geant4 with clhep and Note that if there are no problems building with, I do not anticipate any problems building with Would the geant team please test?

#6 Updated by Kyle Knoepfel about 1 month ago

  • Status changed from New to Feedback

#7 Updated by Lynn Garren about 1 month ago

  • Scope deleted (Internal)
  • Experiment deleted (-)

clhep v2_4_4_1 is now available. Note that LArSoft will be using geant4 v4_10_6_p01c soon when it upgrades to art 3.06.03.

#8 Updated by Julia Yarba about 1 month ago

In a quick try, Geant4 10.6.p01, 10.6.p02, and 10.4.p02 all build fine against clhep v2_4_4_1 (at least if using gcc 9.3.0 compiler and specifying c++17 standard). We are also checking with relevant Geant4 experts if any objections/obstacles can be anticipated when using clhep 2.4.4.x-series with earlier Geant4 releases.

#9 Updated by Julia Yarba about 1 month ago

With the above said, the Geant4 experts state that minor releases of CLHEP are always backward compatible. This means that e.g. Geant4.10.7 should be safe with e.g. CLHEP (required is However, as a general rule, Geant4 is not guaranteed to work with CLHEP release that's notably different from the recommended one. Again, based on our so far experience, Geant4 10.6.p01/p02 or even 10.4.p02 do build with the latest CLHEP However, we can not attest how every particular application based on such build(s) may behave.

#10 Updated by Lynn Garren about 1 month ago

  • Assignee set to Christopher Green
  • Status changed from Feedback to Assigned

Thanks Julia. We understand. Our experience has been that different CLHEP releases usually work.

#11 Updated by Lynn Garren about 1 month ago

I've tagged geant4 v4_10_6_p02c (mu2e) and geant4 v4_10_6_p01d (larsoft) with clhep v2_4_4_1. Source code tarballs are available on SciSoft. The SciSoft team is in the process of providing an art release with clhep v2_4_4_1, and will update this ticket when that is complete.

#12 Updated by Kyle Knoepfel about 23 hours ago

  • % Done changed from 0 to 100
  • Status changed from Assigned to Resolved

Also available in: Atom PDF