Source file downloads

The source files can be downloaded from https://lhapdf.hepforge.org/downloads/

Quick start instructions

If you have a C++11 compiler, building LHAPDF >= 6.2 should be straightforward:

wget https://lhapdf.hepforge.org/downloads/?f=LHAPDF-6.X.Y.tar.gz -O LHAPDF-6.X.Y.tar.gz
# ^ or use a web browser to download, which will get the filename correct
tar xf LHAPDF-6.X.Y.tar.gz
cd LHAPDF-6.X.Y
./configure --prefix=/path/for/installation
make
make install

You will then need to install PDF data files, most easily using the "lhapdf" manager script but also possible by manual download. See the LHAPDF website for details.

On systems where you want to use non-system compilers and libraries, the configure command will need to be a bit more complicated: see the following for more information.

Version 6.2.0 of LHAPDF, and later, have no external library dependencies. Earlier versions rely on the Boost C++ header library. We recommend upgrading to the current series to avoid that complication (and benefit from other improvements, too).

At run-time you may need to set some environment variable: see the next section for details.

Run-time search paths

If you aren't installing LHAPDF into a standard, system-wide location, you will probably need to set some environment variables for it to work at runtime (and perhaps even during the installation).

LHAPDF's primary installation mode is as a shared library, libLHAPDF.so (or libLHAPDF.dylib on Macs). This minimises code duplication and application rebuilds by being the single source of compiled code on your system – executables just refer to libLHAPDF's code symbols at runtime rather than having to "statically" copy them into their own code. (If you really want static linking, make sure to provide the -static flag when linking your application, of point it explicitly at libLHAPDF.a.) Shared libraries need to be locateable at runtime, though, which means that you need to either place them in a standard "system" location, or set an environment variable to add your own custom install paths (usually lib/ or lib64/ within your installation tree) to the library-search mechanism. The environment variable for shared-library searching is LD_LIBRARY_PATH on Linux systems, and DYLD_LIBRARY_PATH on Macs (and FreeBSD).

The same logic applies also to LHAPDF's own executables, which should live in the bin/ directory within your installation tree, and its Python package which typically lives in lib/pythonX.Y/site-packages. The relevant environment variables are respectively PATH and PYTHONPATH for these searches. You may need to set at least the Python search path before installation, since this is under control of Python's own installer mechanism, which can be quite zealous.

A sample environment variable setup, placing a new LHAPDF custom installation under /foo/lhapdf, to be searched after other custom locations, is

export PATH=$PATH:/foo/lhapdf/bin
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/foo/lhapdf/lib
export PYTHONPATH=$PYTHONPATH:/foo/lhapdf/lib/python3.9/site-packages

Build tools

LHAPDF6 just needs your system to have a copy of Make and a C++11 compiler: there is no Fortran code and hence no need for gfortran. We have tested with both the g++ and clang++ compilers.

Note that fairly recent compiler versions are needed, to get C++11 support: g++ >= 4.8.5 and clang++ >= 3.3. The -std=c++11 flag, if needed, will be added automatically by the LHAPDF configure script.

Building LHAPDF is typically straightforward on Linux systems, including CC7 and Ubuntu. Mac OS X, however, can cause problems due to inconsistent compiler and Python versions, and other such fun. If you want to build LHAPDF on a Mac, please see Building on Mac OS X.

Python

If you want to build the Python interface to LHAPDF (which is very nice!), you will need the Python development headers to be installed (e.g. via the python-dev Ubuntu package). If the Python.h header is not found by configure, no Python extension module will be built.

You may also need to make sure that the PYTHONPATH environment variable (see above) is set to include your module-installation directory before installing, if it isn't a system-wide path: Python is sometimes configured to refuse to install to locations not already in the Python search path.

Building LHAPDF

If you have downloaded a release tarball for LHAPDF 6.X.Y, unpack it with tar xf LHAPDF-6.X.Y.tar.gz, then cd to the newly-created directory.

Note: If checking out from version control rather than unpacking a tarball, again cd to the new directory, but you must then also run autoreconf -i before proceeding to the instructions below. There will also be more requirements for external packages if you build this way, since this is the "developer" route to building LHAPDF and requires a bit more expertise.

Now you should run the configure script to analyse your machine, compiler, etc. and set up the Makefiles. You will probably need to provide the --prefix argument to configure to tell it where you want to install LHAPDF (probably you don't want to install to /usr/local, which is the default). For example,

./configure --prefix=$HOME/local

Alternative compilers

If you want to use an alternative C++ compiler, then you can specify the CXX variable on the command line. This is essential on OS X Mavericks and later, where the consistent compiler suite is clang rather than gcc – in that situation, use:

./configure --prefix=... CXX=clang++

The configure script will run and produce quite a bit of output from its various tests. Hopefully everything will be successful: if it gets to the end without stopping due to an error then all is well.

Then just call make to build the library (or e.g. make -j4 to compile 4 files in parallel – if your machine has enough processor cores to do so, even -j2 will speed up the build quite a bit). To install LHAPDF to the --prefix location that you specified, call make install. You will (or at least should(!) find installed files in $prefix/lib, $prefix/include/LHAPDF, and $prefix/share/LHAPDF.

Building on Mac OS X

Builds are typically straightforward on Linux, but Mac OS X unfortunately has a long history of incoherent system compiler setups, which have been worked around manually by users' private installations of Fink, MacPorts, HomeBrew and manual tarball installations of required tools. These work-arounds can themselves be the source of problems when the native compilers or Python libraries get updated, and due to the ad hoc nature of such installations we are restricted in how much we can help to get LHAPDF to compile on a broken system: it is the user's responsibility to make sure that their machine has a consistent set of build tools!

From experience, the simplest reliable route seems to be to run a fresh copy of OS X 10.9 Mavericks (or later) without any additional manual compiler installations: if you use the clang++ compiler on such a system, LHAPDF6 building should "just work".

Note: At the time of writing there is a bug in the Mac Python version which requires that you call export CPPFLAGS=-Qunused-arguments and export CFLAGS=-Qunused-arguments before building. Alternatively you can run the configure script with --disable-python, which avoids the bug at the cost of not building the very useful Python interface to LHAPDF.

The Mac OS X "Homebrew" system (http://brew.sh/) comes recommended by several LHAPDF developers. Many HEP packages are already available for Homebrew via the homebrew-hep project: http://davidchall.github.io/homebrew-hep/ . Success has also been reported with the MacPorts system (http://www.macports.org/). With both these approaches, you should set your environment to only use compilers and Python from the Brew/Ports area and to ignore the system packages: a hybrid approach will only cause unnecessary pain.

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