Comment 5 for bug 1769271

Hi,

That's what I mean. If you want full reproductibility you can add the following line:

=== modified file 'madgraph/interface/common_run_interface.py'
--- madgraph/interface/common_run_interface.py 2018-04-28 21:38:38 +0000
+++ madgraph/interface/common_run_interface.py 2018-05-07 18:58:48 +0000
@@ -5607,6 +5607,8 @@
         """This is run on quitting the class. Apply here all the self-consistency
         rule that you want. Do the modification via the set command."""

+ import random
+ random.seed(self.run_card['iseed'])
         ########################################################################
         # LO specific check
         ########################################################################

You can actually set such random see basically anywhere (especially if you always set it to zero which is fine as well). In that case, you can set it to zero within ./bin/mg5_aMC

Cheers,

Olivier

> On 7 May 2018, at 20:40, Zachary Marshall <email address hidden> wrote:
>
> Just a quick nudge. I looked through the code and don't see any
> indication of another seed in the run card. I looked through the update
> notes and as much documentation as I could find and I don't see any
> indication of either a different seed or a change in behavior. I looked
> through the uses of random, and most seem to seed off of iseed (as I'd
> hoped). I hope you don't mean that we now need to hack the code to add
> a setting of the seed for the python random module based on iseed --
> surely that should be centrally done.
>
> Thanks again,
> Zach
>
> --
> You received this bug notification because you are subscribed to
> 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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