APFELgrid: A high performance tool for parton density determinations

We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and as evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy. Program Summary Program Title: APFELgrid Program Files doi: http://dx.doi.org/10.17632/mhwjt5nsg7.1 Licensing provisions: MIT license Programming language: C++ Nature of problem: Fast computation of hadronic observables under the variation of parton distribution functions. Solution method: Combination of interpolated weight grids from APPLgrid files and evolution factors from APFEL into efficient FastKernel tables. External routines/libraries: APPLgrid, APFEL