HOPPET: Higher Order Perturbative Parton Evolution Toolkit
HOPPET is a Fortran 95 package for carrying out DGLAP evolution and other common manipulations of parton distribution functions (PDFs).
Within HOPPET, PDFs are represented on a grid in x-space so as to avoid limitations on the functional form of input distributions. Decent speed and accuracy are obtained through the representation of splitting functions in terms of their convolution with a set of piecewise polynomial basis functions, and Runge-Kutta techniques are used for the evolution in Q.
Unpolarised evolution is provided in the MSbar scheme to NNLO in the coupling, including heavy-quark thresholds, and polarised evolution to NLO. The code is structured so as to provide simple access to the objects representing splitting function and PDFs, making it possible for a user to extend the facilities already provided.
The latest version can always be obtained from
git clone https://github.com/gavinsalam/hoppet
Details of changes are to be found in the file ChangeLog, while summaries of changes between releases are in ReleaseNotes.
You will need a Fortran 95 compiler to compile this package.
The gfortran compiler is widespread. Versions upwards of 4.3 are OK. Older versions (which might be present on legacy systems) generate incorrect code for HOPPET and should be avoided. The code is acceptably fast, though in tests some years ago was not quite as fast as with commercial compilers.
The code has also been tested with the intel (ifort, versions 8.1.033 upwards) and lahey (lf95) compilers.
For details see the INSTALL file. To get moving quickly, just specify an installation prefix and a fortran compiler (FC), and then do
./configure --prefix="..." FC="..." make make check make install [if you're interested] make install-mod [if you want the f90 module files installed too]
This is not autotools based: if you're used to more advanced usage of autotools scripts, you'll be disappointed here...
The main example program is example_f90/tabulation_example.f90
An equivalent program with the startup, pdf initialisation and evolution spread across different subroutines is given as tabulation_example_2.
An equivalent program based on the streamlined interface is given as tabulation_example_streamlined.
Some users may prefer a pure f77 interface. Corresponding examples are to be found in the example_f77/ directory. Look inside the suppplied Makefile and if need be edit it manually.
cd ../example_f77 # <edit the Makefile directly> # compile make tabulation_example # run the program. Should give output identical to that from # example_f90/tabulation_example ./tabulation_example
In the same directory there is a C++ example
make cpp_tabulation_example ./cpp_tabulation_example
which again does the same things (though in this case it uses the simpler of the two streamlined initialization calls).
Other programs provided in the example_f77/ directory illustrate the use of the streamlined interface in conjunction with LHAPDF (compare_lhapdf_hoppet.f), and show how to use the feature of getting convolutions with splitting functions (convolution_example.f).
The benchmarking/ directory contains the programs used for the full benchmarking, accuracy and precision testing.
When the hoppet library is being built, on some systems the following warnings may be reported
/usr/bin/ranlib: file: libhoppet_v1.a(hoppet_v1.o) has no symbols /usr/bin/ranlib: file: libhoppet_v1.a(types.o) has no symbols ranlib: file: libhoppet_v1.a(hoppet_v1.o) has no symbols ranlib: file: libhoppet_v1.a(types.o) has no symbols
These warnings do not indicate an actual problem. They are simply a consequence of the fact that some of the source (.f90) files contain only information about interfaces and constants, so that the resulting object (.o) files are essentially empty.
The master branch provides the official HOPPET release. Two additional branches are in use for specific physics applications: