= The WHIZARD / O'Mega interface (C. Speckner) --- UNDER CONSTRUCTION =

== Overview ==
The WHIZARD / O'Mega interface generates the model files necessary for the inclusion of a FeynRules model into the WHIZARD / O'Mega framework. All versions of WHIZARD / O'Mega >= 1.92 are supported.

== Usage: all versions ==
As all other interfaces, the WO interface is invoked by calling {{{WriteWOOuput}}}. Three syntax variants are admissible:

1. {{{WriteWOOutput[Lagrangian, Options]}}}

2. {{{WriteWOOutput[{LagrangianList}, Options]}}}

3. {{{WriteWOOutput[Null, WOVertexList->{VertexList}, Options]}}}

Version 1. operates on a single Lagrangian, while 2. operates on a list of Lagrangians and 3. takes a list of FeynmanRules as an argument. The following options are available:

 * {{{WOVertexList}}}: If {{{=!= Null}}}, this is interpreted as a list of Feynman rules and overrides any Lagrangian (or -list) specified (in this case, {{{Null}}} is accepted as first argument). Default: Null
 * {{{WOModelName}}}: The name by which the model will be identified in WO. Note that all models for W1.9x have to start with "fr" (e.g. {{{WOModelName->"fr_sm"}}}) if they are to be picked up by WO1.9x without user intervention (no such restriction exists for W2). Beware that the interface my modify this name if it doesn't fit into the WO naming schemes --- double check the generated messages to be sure. Default: derived from the FR model name
 * {{{WOMaxNcf}}}: Upper limit on the number of generated color flows which the generated code will be able to handle (essentially n_8 - n_3 / 2, where n_8 is the maximum number of external octets and n_3 that of external triplets). Irrelevant for W2; also, the technically experienced user can change this after generation in {{{f90_modellname_Col.ml}}}. Default: 4
 * {{{WOGauge}}}: The following gauges are available:
  * {{{WOUnitarity}}}: Unitarity gauge (default)
  * {{{WOFeynman}}}: Feynman gauge
  * {{{WORxi}}}: Rxi gauges. In this case, you __must__ define a parameter taking the role of \xi and pass it to the interface via {{{WOGaugeParameter}}} (see below).
 * {{{WOGaugeParameters}}}: The parameter which takes the role of \xi in the Rxi gauges, can be either a string or a symbol. Default: "Rxi"
 * {{{WOWhizardVersion}}}: Select the WO version for which you want to generate code. Possible choices:
  * {{{"1.92"}}}: WO 1.92
  * {{{"1.93"}}}: WO 1.93 - 1.95
  * {{{"2.0" }}}: WO 2.0 (default)
 * {{{WOVerbose}}}: Verbose output. At the moment, this gives detailed information on skipped vertices. Default: False
 * {{{WOAutoGauge}}}: Automagically assign goldstone boson masses.. Default: True
 * {{{WOMaxCouplingsPerFile}}}: The maximum number of couplings written into a single FORTRAN file. Reduce this number if you run into trouble compiling the generated code. Default: 500
 * {{{WORunParameters}}}: A list of all parameters which are recalculated when \alpha_s changes. Without effect for WO1.9x output. Default: {G, aS}
 * {{{WOFast}}}: Set this to False to enable more time consuming checks for known lorentz structures if you have trouble with skipped couplings. Default: True
 * {{{Output}}}: The output directory which will contain the generated model files. Default: derived from the FR model name

It is wise to '''check the messages the interface generates''' while it runs; i these will inform you about any unidentified vertices that have been skipped as well as of most other noteworthy caveats concerning the generated code.

== Usage: 1.9x particularities ==
In order to use the interface with WO 1.9x, the build system of WHIZARD must be patched and the model files copied to the proper locations in the tree. This is taken care of by the script called {{{inject}}} which is created by the interface in the output directory. The basic usage is (from within the output directory):

{{{./inject [options] path_to_whizard}}}

Running {{{./inject --help}}} will give a full overview over the supported options. After "injecting", the model is available in WHIZARD and will behave like the stock ones. However, some caveats exist for the unwary, so '''pay attention to the scripts output messages''' and be sure to '''read through this list carefully''':

 * The inject script has been designed to avoid any accidental change of existing data. Therefore, if a FeynRules model of the same name already exists, it will not be overwritten by default (the script will inform you if a file is being skipped though). To enforce overwriting of existing files, use the {{{--force}}} option.
 * If the number of distinct couplings changes significantly, the number of generated FORTRAN files may change. This can lead to problems with spurious files from a previous run being present in the WHIZARD tree, potentially wreaking havoc on the WHIZARD compilation. The script will inform you of such conflicts, and you can then rerun it with the {{{--cleanup}}} option to remove the conflicting files automatically.
 * Be sure to reconfigure WHIZARD (rerun the configure script) after injecting a model. Also, if the compilation fails, a {{{make clean}}} or {{{make realclean}}} in the WHIZARD tree can help to put a borked tree into a sane state again (take care as those remove your input files, so make copies before).
 * In order for the model to be picked up by WHIZARD, the WO mode name must start with "fr". This is taken care of automatically if the interface assigns it, but if you reset it via {{{WOModelName}}}, it is your responsibility to pick a proper name.
 * Writing multiple models to one output directory is possible and supported.