[Rivet] Compatibility of YODA reference data from Rivet with HEPData

[Graeme Watt]

Dear Rivet developers,

I wrote a Python script to compare a YODA reference data file, intended 
for inclusion in Rivet, with the corresponding YODA file downloaded from 
HEPData:

https://github.com/HEPData/miscellaneous/blob/master/scripts/yoda_compare_hepdata.py
   Example usage:  ./yoda_compare_hepdata.py ATLAS_2017_I1614149.yoda -i 
1614149 -a

This means: compare a local YODA file "ATLAS_2017_I1614149.yoda" with a 
YODA file downloaded from the HEPData record with INSPIRE ID "1614149" 
and also compare YODA annotations "-a".  Since the HEPData YODA file 
might contain additional analysis objects compared to the Rivet YODA 
file, and since there might be inconsequential rounding errors or 
differences in number formats, comparison using a simple "diff" of .yoda 
files is not always adequate.

I had a few problems with the YODA 1.7.0 software when writing the 
Python script, which could perhaps be improved in future:

* Calling dump() on Scatter objects does not output the same format as 
in the input .yoda files, e.g. dumping a Scatter2D gives "HISTO1D" in 
the output and the central value of the x bin is not output.  This might 
be due to deficiencies in 
https://yoda.hepforge.org/trac/browser/src/WriterFLAT.cc .
* I expected to be able to check (fuzzy) equality of two Scatter objects 
using "s == s1", which seems to be implemented in C++ but not in Python.
* Checking (fuzzy) equality of two Point2D objects using "p == p1" is 
implemented in Python, but it only compares the x axes and not the y 
axes.  Similarly, for Point3D objects, the (fuzzy) equality operator 
"==" only compares the x and y axes, but not the z axes.
* In the end, I just copied the definition of "fuzzyEquals" from the C++ 
code into my script and did my own comparisons, without relying on the 
"==" operator for Point or Scatter objects.

Recall that Holger Schulz made some similar comparisons in 2016 between 
YODA reference data files from Rivet and from the old HepData, where he 
found significant inconsistencies:

https://www.hepforge.org/lists-archive/rivet/2016-October/007318.html
https://rivet.hepforge.org/trac/browser/contrib/devscripts/HepDataConsistency

While fixing all Rivet/HEPData inconsistencies is probably unrealistic 
for now, we could at least start by ensuring that analyses added to new 
Rivet releases include a YODA file that's compatible with the YODA 
download given by HEPData.  My new script should be useful for these 
purposes.  (This work was prompted by a conversation with Peter Skands 
and Jon Butterworth last month in Durham.)  You're welcome to modify my 
script as you need and include it in a future Rivet release.  The script 
could be run by the experiment contact persons before they upload new 
analyses to the Rivet "contrib" area.  It could also be run (perhaps in 
a more automated way) by the Rivet developers when moving analyses from 
the "contrib" area to a new Rivet release.  I just ran the script for 
all the new analyses in the current Rivet "contrib" area ( 
https://www.hepforge.org/archive/rivet/contrib/ ) and it already turned 
up some useful information:

* ATLAS_2014_I1310835, ATLAS_2017_I1614149, and ATLAS_2017_I1624693, are 
all compatible with HEPData.
* ATLAS_2016_I1502620 has multiple .yoda files which can't be handled by 
my script.
* ATLAS_2017_I1625109 showed some apparent inconsistencies but the 
problem looks to be on the HEPData side.  The dataset index starts at 0 
(instead of 1) due to a bug in the hepdata-converter package (which I'll 
fix) and the year in the analysis name is 2018 (instead of 2017) taken 
from the journal publication.
* ALICE_2017_I1620477 is incompatible with HEPData.
* CMS_2016_I1487277 is compatible with HEPData.
* CMS_2012_I1111014 and CMS_2016_I1491950 are incompatible with HEPData.
* CMS_2017_I1499471, CMS_2017_I1635889, CMS_2018_I1662081 and 
CMS_2018_I1663958 are all missing from HEPData.
* CMS_2017_I1605749 has a HEPData record, but the YODA conversion fails 
due to a problem with the original HEPData submission.
* LHCF_2015_I1351909 is compatible with HEPData, but the annotations differ.
* LHCF_2016_I1385877 is incompatible with HEPData.

I hope this gives you something to discuss at this week's Rivet 
workshop! :-)

Best regards,
Graeme Watt (HEPData)

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