General concept
fastNLO provides the code to create, fill, read, and evaluate fast interpolation
tables of pre-computed coefficients in perturbation theory for observables
in hadron-induced processes. This allows fast theory predictions of these
observables for arbitrary parton distribution functions (of regular shape),
renormalization or factorization scale choices, and/or values of alpha_s(Mz)
as e.g. needed in PDF fits or in systematic studies. Very time consuming
complete recalculations are thus avoided.
Code
The new code release fastNLO Toolkit (v2.5) provides an extended grid format
that may contain in so-called InfoBlocks information on the relative numerical
uncertainty of each contribution of a fixed-order calculation. The tool fnlo-tk-modify
has been updated to allow addition of such information to an interpolation table
directly from NNLOJET .dat files, log files of fnlo-tk-statunc applied to a sample
of NLOJet++ grids, or a text file. Numerous other improvements serve the adaptation
to grid production with the NNLOJET program via the APPLfast interface.
New code named the fastNLO Toolkit (v2.3) has been made available in the form
of a prerelease (beta release). The toolkit provides a library with all
functionality to create, fill, read, and evaluate interpolation tables
in the fastNLO format. It comes with a much improved structure that allows
other programs to be interfaced to fastNLO. The only dependency is to
the LHAPDF package for the evaluation part. Essentially, it will replace
the former fastNLO Reader (v2.1) package.
The interface from NLOJet++ to fastNLO is also available as a prerelease
and requires a patched version of NLOJet++ and the fastNLO Toolkit. It is
recommended to use it in connection with FastJet for the various jet algorithms.
DiffTop has been interfaced to the fastNLO Toolkit and the latest prerelease
works with Sherpa via a yet to be relased update of the MCgrid package.
An interface to Herwig++ MatchBox is in preparation.
Previously, table evaluation code was released in the form of the fastNLO Reader
(v2.1) package. This fastNLO Reader package consists of two independent parts:
a C++ library including a documented example, and a Fortran program inherited from
the previous fastNLO version 1.4 with somewhat less capabilities. When applicable
both codes give the same results at double precision accuracy.
The C++ version is capable of evaluating all version 2.1 fastNLO tables
(fixed-scale and flexible-scale tables except for some new HERA tables that cannot
be read yet) with identical results compared to the toolkit C++ reader.
The v2.1 Fortran code is also generic in the sense that it reads all fixed-scale tables
within its capabilities, however, because of the lack of dynamic memory allocation
it might be necessary to adapt the array dimensioning for particular scenarios, which entails a
recompilation. In that case the user receives a warning and execution is stopped.
All packages can be downloaded as autotools-based distribution tar-balls via
the links in the sidebar.
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