Systematics with EWA: IndexError : list index out of range

[Richard Ruiz]

Hi folks,

I am using the latest version of v3.6.0 via git. When running systematics with EWA, the module crashes after computation with an "IndexError" related to the number of cross sections being reweighted.

I see the problem (mostly) in the relevant lines of madgraph/various/systematics.py but I do not see the solution, so I am posting things here. The issue appears in earlier releases but unsure how far back.

More details on reproducing the problem below! Let me know if more information is needed. I am curious how to solve this.

cheers,
Richard

Process:

set group_subprocesses false
set gauge Feynman

generate w+ w- > t t~ QED=2 QCD=0
output EVAbenchTest_wxwx_tt_XLO_v3_6_0

launch EVAbenchTest_wxwx_tt_XLO_v3_6_0
set no_parton_cut
set ebeam 5000
set nevents 40k
set lpp1 -4 # setup beam1 as anti-muon
set lpp2 4 # setup beam2 as muon
set pdlabel eva
set fixed_fac_scale1 false
set fixed_fac_scale2 false
set dynamical_scale_choice 4
set scalefact 0.5
set ievo_eva 0 # (0=q^2 or 1=pT^2)
set use_syst true
done

Terminal output:
INFO: #***************************************************************************
#
# original cross-section: 0.026986220000019497
# scale variation: +35.8% -30.4%
# central scheme variation: +35.8% -16.9%
# PDF variation not available for EVA.
#
# dynamical scheme # 1 : 0.0246264 +35.9% -28.1% # \sum ET
# dynamical scheme # 2 : 0.0313445 +33.1% -28.5% # \sum\sqrt{m^2+pt^2}
# dynamical scheme # 3 : 0.0224194 +39.8% -33.4% # 0.5 \sum\sqrt{m^2+pt^2}
# dynamical scheme # 4 : 0.0366433 +30.3% -26.4% # \sqrt{\hat s}
#***************************************************************************

INFO: End of systematics computation
INFO: # Events generated with EVA PDF.
INFO: # Will Compute 45 weights per event.
Command "generate_events run_01" interrupted with error:
IndexError : list index out of range
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/.../EVAbenchTest_wxwx_tt_XLO_v3_6_0/run_01_tag_1_debug.log'.
Please attach this file to your report.
INFO: storing files of previous run
INFO: Done
INFO:

Log output:
 File "/home/richard/Scripts/MadGraph/MGaMC_git_3_x_EVA_NLP/madgraph/interface/common_run_interface.py", line 1999, in do_systematics
    sys_obj.print_cross_sections(all_cross, nb_event, result_file)
  File "/home/richard/Scripts/MadGraph/MGaMC_git_3_x_EVA_NLP/madgraph/various/systematics.py", line 497, in print_cross_sections
    to_print.append(all_cross[i])
                  ~~~~~~~~~^^^
IndexError: list index out of range

madgraph/various/systematics.py lines 487-499:

all_cross = [c*norm for c in all_cross]
stdout.write("# mur\t\tmuf\t\talpsfact\tdynamical_scale\tpdf\t\tcross-section\n")
for i,arg in enumerate(self.args):

            to_print = list(arg)
            if self.banner.run_card['pdlabel']=='eva':
                to_print[4] = 0
            else:
                to_print[4] = to_print[4].lhapdfID

            to_print.append(all_cross[i]) <~~~~~ this is the offending line
            to_report = []
            stdout.write('%s\t\t%s\t\t%s\t\t%s\t\t%s\t\t%s\n' % tuple(to_print))