way to not quit on 'Zero result detected: No Phase Space'

Asked by Wojciech Kotlarski on 2020-08-03

Dear Authors,

We're calculating cross sections for many SUSY processes at once, making a loop over different parameter cards. For some of the param cards, we get a message
'Zero result detected: No Phase Space`
This forces MG to quit. Is there a way to circumvent it, such that for a given subprocess MG just prints 0. While few channels might be kinematically forbidden for a given point, others are allowed.

Best Regards,

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Do you use the built-in scan mode?
With it I do not reproduce your issue:
Here is the script that I use to run the code:
generate h > b b~
set mb scan:[5,100,20]

and the output file is the following:
#run_name mass#5 cross
run_01 5.000000e+00 5.384700e-03
run_02 1.000000e+02 0.000000e+00
run_03 2.000000e+01 4.623500e-03



PS: actually even outside of that scan mode, I do not have it crashing.
Did you change the configuration file to change the value of the parameter crash_on_error?

No, we don't use the scan feature. Here's a simple example that reproduces this issue. Generate

generate e+ e- > t t~
add process e+ e- > b b~

and set the sqrtS to 200 GeV. This gives

Working on SubProcesses
INFO: P1_ll_ttx
INFO: P2_ll_bbx
 P1_ll_ttx SubProcesses doesn't have available phase-space.
            Please check mass spectrum.
INFO: Idle: 0, Running: 1, Completed: 0 [ current time: 00h31 ]
INFO: Idle: 0, Running: 0, Completed: 1 [ 0.18s ]
INFO: Idle: 0, Running: 0, Completed: 1 [ 0.18s ]
INFO: End survey
refine 10000
Creating Jobs
INFO: Refine results to 10000
INFO: Generating 10000.0 unweighted events.
Error when reading /mnt/ramdisk/MG5_aMC_v2_7_3_py3/wojciech/test/SubProcesses/P1_ll_ttx/G1/results.dat
Command "generate_events " interrupted with error:
FileNotFoundError : [Errno 2] No such file or directory: '/mnt/ramdisk/MG5_aMC_v2_7_3_py3/wojciech/test/SubProcesses/P1_ll_ttx/G1/results.dat'
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/mnt/ramdisk/MG5_aMC_v2_7_3_py3/wojciech/test/run_02_tag_1_debug.log'.
Please attach this file to your report.

As you can see, we're using the newest version of MG (the python3 variant).



then i followed the method described here:

and used the following script:

import model sm
generate p p > t t~
add process p p > b b~
set ebeam 50
set ebeam 100
set ebeam 200
launch -i
print_results --path=./cross_section_top.txt --format=short

and i get:
[python3]$ cat cross_section_top.txt
# run_name tag cross error
run_01 tag_1 266492.2 419.16044565297426 10000
run_02 tag_1 1335185.0 1587.5871412933527 10000
run_03 tag_1 4852500.000000002 5655.745377932073 10000

This is with the python3 branch... so I still fail to reproduce your issue.
Could you send me the script that you use to reproduce this? Are you using a cluster mode run? (This maybe related...)

In short can you copy/paste the file /mnt/ramdisk/MG5_aMC_v2_7_3_py3/wojciech/test/run_02_tag_1_debug.log (or create a bug report such that you can attach it).



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