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diff --git a/doc/sphinx/scales.rst b/doc/sphinx/scales.rst
index 9378351..646855d 100644
--- a/doc/sphinx/scales.rst
+++ b/doc/sphinx/scales.rst
@@ -1,69 +1,69 @@
.. _`Custom scales`:
Custom scales
=============
Reversed HEJ comes with a small selection of built-in renormalisation
and factorisation scales, as described in the :ref:`scales <scales>` setting. In
addition to this, user-defined scales can be imported from custom
libraries.
Writing the library
-------------------
Custom scales are defined through C++ functions that take an event and
compute the corresponding scale. As an example, let's consider a
function returning the transverse momentum of the softest jet in an
event. To make it accessible from reversed HEJ, we have to prevent C++
name mangling with :code:`extern "C"`:
.. code-block:: C++
#include "RHEJ/Event.hh"
extern "C"
double softest_jet_pt(RHEJ::Event const & ev){
const auto softest_jet = sorted_by_pt(ev.jets()).back();
return softest_jet.perp();
}
After saving this code to some file :code:`myscales.cc`, we can compile
it to a shared library. With the :code:`g++` compiler this can be done
with the command
.. code-block:: sh
g++ -fPIC -shared -Wl,-soname,libmyscales.so -o libmyscales.so myscales.cc
If :code:`g++` is used and the library also contains other definitions,
it is recommended to add :code:`-fvisibility=hidden` to the compiler
flags and :code:`__attribute__((visibility("default")))` after
:code:`extern "C"` for each exported function in order to avoid possible
name clashes.
Importing the scale into reversed HEJ
-------------------------------------
Our custom scale can now be imported into reversed HEJ by adding the
-lines
+following lines to the `YAML <http://yaml.org/>`_ configuration file
.. code-block:: YAML
import scales:
/path/to/libmyscales.so: softest_jet_pt
It is also possible to import several scales from one or more libraries:
.. code-block:: YAML
import scales:
/path/to/libmyscales1.so: [first_scale, second_scale]
/path/to/libmyscales2.so: [another_scale, yet_another_scale]
The custom scales can then be used as usual in the :ref:`scales <scales>`
setting, for example
.. code-block:: YAML
scales: [H_T, softest_jet_pt, 2*softest_jet_pt]

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