Hi,

The (hidden) additional parameter is coded in the following push/patch:
https://bazaar.launchpad.net/~mg5core2/mg5amcnlo/2.6.3/revision/279

Cheers,

Olivier



On 7 May 2018, at 22:44, Zachary Marshall <<email address hidden><mailto:<email address hidden>>> wrote:

Hi Oliver,

Yes, we're usually calling things from a shell.  I would think this
would also make life easier on you all -- ensuring good reproducibility
means that you can more easily debug problems when they arise.  Having a
switch in the run card would be fine with me.

Best,
Zach

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MadGraph5_aMC@NLO.
https://bugs.launchpad.net/bugs/1769271

Title:
 Reproducibility problem in 2.6.2 (in combine?)

Status in MadGraph5_aMC@NLO:
 New

Bug description:
 Dear authors,

 I'm running tests with MG5_aMC 2.6.2 - in case you have a CERN account, it's this one:
 /afs/cern.ch/sw/lcg/external/MCGenerators_lcgcmt67c/madgraph5amc/2.6.2.atlas/x86_64-slc6-gcc47-opt/

 We see some non-reproducibility, even when setting a random number
 seed.  I attach a tarball of the cards directories so that you have
 the run, param, and proc cards.  For the actual runs, iseed was set to
 1234 (of course, the code resets it to 0 after the run).

 Looking at the LHE files, they seem to contain the same events, but in
 different order.  Just diffing the two files, you can see an example
 right away:

 1487a1488,1496
6      1 +8.9242237e-05 3.75379100e+02 7.95049700e-03 1.05265500e-01
      21 -1    0    0  501  502 +0.0000000000e+00 +0.0000000000e+00 +2.1196628570e+01 2.1196628570e+01 0.0000000000e+00 0.0000e+00 -1.0000e+00
       2 -1    0    0  502    0 -0.0000000000e+00 -0.0000000000e+00 -1.6619322556e+03 1.6619322556e+03 0.0000000000e+00 0.0000e+00 -1.0000e+00
      24  2    1    2    0    0 +8.9075749711e+01 +3.5726986208e+01 -1.0898807218e+03 1.1239759236e+03 2.5743150990e+02 0.0000e+00 0.0000e+00
 1000023  1    3    3    0    0 +8.0116545705e+01 +1.1392922116e+02 -6.6081705506e+02 6.8029530983e+02 8.2000000000e+01 0.0000e+00 -1.0000e+00
 1000024  1    3    3    0    0 +8.9592040060e+00 -7.8202234949e+01 -4.2906366674e+02 4.4368061374e+02 8.1000000000e+01 0.0000e+00 1.0000e+00
       1  1    1    2  501    0 -8.9075749711e+01 -3.5726986208e+01 -5.5085490525e+02 5.5915296062e+02 0.0000000000e+00 0.0000e+00 -1.0000e+00
</event>
<event>
 1506,1532c1515,1542
 <  6      1 +8.9242237e-05 3.75379100e+02 7.95049700e-03 1.05265500e-01
 <        21 -1    0    0  501  502 +0.0000000000e+00 +0.0000000000e+00 +2.1196628570e+01 2.1196628570e+01 0.0000000000e+00 0.0000e+00 -1.0000e+00
 <         2 -1    0    0  502    0 -0.0000000000e+00 -0.0000000000e+00 -1.6619322556e+03 1.6619322556e+03 0.0000000000e+00 0.0000e+00 -1.0000e+00
 <        24  2    1    2    0    0 +8.9075749711e+01 +3.5726986208e+01 -1.0898807218e+03 1.1239759236e+03 2.5743150990e+02 0.0000e+00 0.0000e+00
 <   1000023  1    3    3    0    0 +8.0116545705e+01 +1.1392922116e+02 -6.6081705506e+02 6.8029530983e+02 8.2000000000e+01 0.0000e+00 -1.0000e+00
 <   1000024  1    3    3    0    0 +8.9592040060e+00 -7.8202234949e+01 -4.2906366674e+02 4.4368061374e+02 8.1000000000e+01 0.0000e+00 1.0000e+00
 <         1  1    1    2  501    0 -8.9075749711e+01 -3.5726986208e+01 -5.5085490525e+02 5.5915296062e+02 0.0000000000e+00 0.0000e+00 -1.0000e+00
 < </event>


 I believe that's the same event, but note that the line numbers are ~20 apart -- this event is first in one file and fourth in the other.  I believe this indicates some non-reproducibility or a race condition in combine somewhere.

 Because these events then enter programs like Pythia8 -- or even when
 they enter MadSpin -- the events are processed in order, the final
 events then appear random (different seeds are applied to the same
 particles).  That means the events are effectively not reproducible
 when processed through, so this is an issue for our bug hunting and
 for various other reasons.

 If you could help us out with this it would be very much appreciated!

 Thanks,
 Zach

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