How to reproduce an NNPDF4.0 fit
Here we describe how to reproduce the NNPDF4.0 PDF sets that are publicly available through LHAPDF as discussed in section 10 of the NNPDF4.0 paper [BallCarrazzaCruzMartinez+21].
The files needed to reproduce the results are available in the folder
of the project repository on Github. The
.yml files that folder are the following:
nnpdf40_env.yml # conda environment NNPDF40_hyperopt.yml # hyperoptimization runcard # Fit runcards: NNPDF40_lo_as_0118_pch.yml NNPDF40_lo_as_0118.yml NNPDF40_nlo_as_0117.yml NNPDF40_nlo_as_0118_pch.yml NNPDF40_nlo_as_0118.yml NNPDF40_nlo_as_0119.yml NNPDF40_nnlo_as_0116.yml NNPDF40_nnlo_as_01175.yml NNPDF40_nnlo_as_0117.yml NNPDF40_nnlo_as_0118_1000.yml NNPDF40_nnlo_as_01185.yml NNPDF40_nnlo_as_0118_pch.yml NNPDF40_nnlo_as_0119.yml NNPDF40_nnlo_as_0120.yml NNPDF40_nnlo_pdfas.yml NNPDF40_nnlo_as_0118_hessian.yml # Hessian conversion runcard
Below we will describe how these runcards can be used to generate the NNPDF4.0 PDF grids.
Setting up the NNPDF4.0 conda envirnoment
The exact conda environment, including all transitive dependencies, used to produce all the publicly released PDF fits has been preserved to ensure precise reproducibility. The environment can be found in the project repository It can be generated and activated by running
conda env create --file nnpdf40_env.yaml conda activate nnpdf40
Alternatively, we provide a ready to run docker image with a pre-installed environment. After setting it up, you can download and open the environment by running
docker run -it ghcr.io/nnpdf/nnpdf:4.0.3 bash
Hyperoptimization for NNPDF4.0
NNPDF40_hyperopt.yml runcard can be used to run the
hyperoptimization with the exact same settings used
to identify the NNPDF4.0 architecture. This step can be skipped if the aim is
simply to reproduce the NNPDF4.0 grids, which requires using the exact same
architecture as was used to create the NNPDF4.0 grids. Nevertheless, this
runcard is made available to provide a complete overview of each step in the
production of the NNPDF4.0 sets.
Producing the NNPDF4.0 fits
After setting up the conda environment, we can use it to produce the fits in the
usual way. The names of the “fit runcards” listed in the
textblock above are the same as those of
the corresponding (public) LHAPDF grids of the same name. For example,
baseline fit with \(\alpha_s(m_Z)=0.118\) and a variable-flavor-number
scheme with up to five active flavors can be generated with
Hessian conversion, compression, bundled sets and flavor number variations
Among the released PDF sets of NNPDF4.0 are also some sets that are the result of a transformation or combination of the fits produced using the “fit runcards”, these PDF grids are:
# Baseline NNDPF4.0 sets: NNPDF40_nnlo_as_0118 NNPDF40_nnlo_as_0118_hessian # PDF sets with :math:`\alpha_s` variations: NNPDF40_nnlo_pdfas NNPDF40_nnlo_hessian_pdfas # PDF sets with flavor-number variations: NNPDF40_nlo_as_0118_nf_4 NNPDF40_nlo_as_0118_nf_6 NNPDF40_nnlo_as_0118_nf_4 NNPDF40_nnlo_as_0118_nf_6 NNPDF40_nlo_pch_as_0118_nf_3 NNPDF40_nnlo_pch_as_0118_nf_3 NNPDF40_nlo_as_0118_nf_4_pdfas NNPDF40_nnlo_as_0118_nf_4_pdfas
Section 10 of the NNPDF4.0 states how these can be obtained from the fits produced using the method discussion under Producing the NNPDF4.0 fits, but we will again give some pointers here.
NNPDF40_nnlo_as_0118_hessian are based on
a 1000 replica PDF set
NNPDF40_nnlo_as_0118 is the result of a compression of
NNPDF40_nnlo_as_0118_1000 using the
pycompressor package, while
NNPDF40_nnlo_as_0118_hessian can be created by running
For more information, see the tutorial on how to transform a Monte Carlo PDF set into a Hessian PDF set.
The bundled PDF + \(\alpha_s\) variation set
NNPDF40_nnlo_pdfas can be
generated using the runcard
NNPDF40_nnlo_as_0118_1000.yml, again, for more
information on how to bundle PDFs with \(\alpha_s\) replicas, see
the relevant tutorial.
The PDF sets released as part of NNPDF4.0 also includes sets in which the
maximum value of
nf differs from the baseline value of
nf=5. To produce
these sets, the steps described in How to create PDF sets with flavor-number variations. In particular,
the ID’s of the required theories can be found in the
where the id’s of the theories used to do the flavor-number variations are
Please note that the Hessian and
_pdfas conversion runcards won’t work
with the 4.0.3 version of the code (and thus the fixed enviroment) and
instead require a version 4.0.4 or newer.