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README
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README
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APFELgrid
=========
The APFELgrid plugin is a tool designed to accelerate the computation of physical observables
at hadron colliders, by means of combining the interpolated weight-grids provided by the APPLgrid
project with the evolution of parton densities provided by APFEL. The tool is aimed at PDF fitting groups,
as it allows for the extremely rapid recalculation of cross-sections when varying the input PDF.
APFELgrid generates FastKernel (or FK) tables which reduce the computation of NLO pQCD predictions
to a particuarly compact form in terms of PDFs at a single initial scale.
These tables are used for fits in the [NNPDF](http://nnpdf.hepforge.org) series of PDF determinations.
The plugin
----------
This package consists of two major parts
+ **The APFELgrid plugin** itself, which performs the combination of APPLgrid tables and APFEL evolution into FK tables.
+ **The FastKernel driver**, which describes the FK file format and provides basic convolution routines.
The APFELgrid code is installed directly as a plugin to APFEL. Its use is demonstrated in the example *example_gen.cc*.
The FastKernel driver is supplied as a single C++ header which may be dropped into users projects where convenient. Included in
the driver are routines for the basic and SIMD accelerated convolution with externally provided PDFs. An example of how to use the
included driver is given in *example_conv.cc*. The FK table format itselfis a simple plaintext format designed such that writing
custom interfaces to it should be simple.
Requirements
------------
+ **APFEL** [2.7.1](http://github.com/scarrazza/apfel)
+ **LHAPDF** [6.X.X](http://lhapdf.hepforge.org)
+ **APPLgrid** [1.4.70](http://applgrid.hepforge.org)
Your APPLgrid installation must be modified such that all headers are installed
(simply copy all headers from /src/ to /appl_grid/ before installation of APPLgrid)
Installation and tests
----------------------
A bootstrap script is provided which downloads and installs the relevant APPLgrid headers,
detects the path of APFEL and configures and compiles the package for installation there.
To use this script and install to the default directory type
./setup.sh
make install
Alternatively, the APPLgrid headers may be installed manually as specified above, and the
installation performed in the typical autotools fashion
(autoreconf -i)
./configure
make
make install
A few tests can be performed upon the package with
make check
which is automatically executed by the boostrap script.
Examples
--------
For usage examples, see
+ **/tests/example_gen.cc** for an FK table generation example
+ **/tests/example_conv.cc** for an FK table convolution example
Documentation
-------------
Documentation is generated with [docco](https://github.com/jashkenas/docco).
./docco_generate.sh
Feedback
--------
For comments or questions please get in contact via github.