Main-Program Settings

Introduction

The main program is up to the user to write. However, sample main programs are provided. In one such class of programs, key settings of the run are read in from a "cards file". These commands may be of two types
(a) instructions directly to Pythia, like which processes to generate, and
(b) instructions to the main program for what it should do, like how many events to generate, i.e. how many times pythia.next() should be called.
In principle these two kinds could be kept completely separate. However, to make life simpler, a number of useful main-program settings are defined on this page, so that they are recognized by the Settings machinery. They can thus be put among the other cards without distinction. It is up to you to decide which ones, if any, you actually want to use when you write your main program. For convenience, some in the second section below can also be interpreted directly by Pythia, while the subsequent ones really have to be used in your main program.

Once you have used the pythia.readFile(fileName) method to read in the cards file, you can interrogate the Settings database to make the values available in your main program. A slight complication is that you need to use a different Settings method for each of the four possible return types that you want to extract. To save some typing the same method names are found directly in the Pythia class, and just send on to the Settings ones to do the job, e.g. 

  bool   showCS = pythia.flag("Main:showChangedSettings");
  int    nEvent = pythia.mode("Main:numberOfEvents");
  double spare1 = pythia.parm("Main:spareParm1");
  string file   = pythia.word("Main:allSettingsFile");

Run settings

Here settings related to how many events to generate and whether to print some information on data used in run. These variables can be set in an input "cards" file, and thereafter read out an used in the user-written main program. Usage is purely optional, but may help you reduce the need to recompile your main program.

mode  Main:numberOfEvents   (default = 1000; minimum = 0)
The number of events to be generated.

mode  Main:numberToList   (default = 2; minimum = 0)
The number of events to list.

mode  Main:timesToShow   (default = 50; minimum = 0)
Print the number of events generated so far, this many times, i.e. once every numberOfEvents/numberToShow events.

mode  Main:timesAllowErrors   (default = 10)
Allow this many times that pythia.next() returns false, i.e. that an event is flawed, before aborting the run.

flag  Main:showChangedSettings   (default = on)
Print a list of the changed flag/mode/parameter/word settings.

flag  Main:showAllSettings   (default = off)
Print a list of all flag/mode/parameter/word settings. Warning: this will be a long list.

mode  Main:showOneParticleData   (default = 0; minimum = 0)
Print particle and decay data for the particle with this particular identity code. Default means that no particle is printed.

flag  Main:showChangedParticleData   (default = off)
Print a list of particle and decay data for those particles that were changed (one way or another).

flag  Main:showChangedResonanceData   (default = off)
In the previous listing also include the resonances that are initialized at the beginning of a run and thus get new particle data, even if these may well agree with the default ones. Warning: this will be a rather long list.

flag  Main:showAllParticleData   (default = off)
Print a list of all particle and decay data. Warning: this will be a long list.

flag  Main:writeChangedSettings   (default = off)
Write a file with the changed flag/mode/parameter/word settings, in a format appropriate to be read in at the beginning of a new run, using the pythia.readFile(fileName) method.

word  Main:changedSettingsFile   (default = currentSettings.cmnd)
The name of the file to which the changed flag/mode/parameter/word settings are written if Main:writeChangedSettings is on.

flag  Main:writeAllSettings   (default = off)
Write a file with all flag/mode/parameter/word settings, in a format appropriate to be read in at the beginning of a new run, using the pythia.readFile(fileName) method.

word  Main:allSettingsFile   (default = allSettings.cmnd)
The name of the file to which a flag/mode/parameter/word settings are written if Main:writeAllSettings is on.

flag  Main:showAllStatistics   (default = off)
Print all available statistics or only the minimal set at the end of the run.

Subruns

You can use subruns to carry out several tasks in the same run. In that case you will need repeated instances of the first setting below in your command file, and could additionally use the second and third as well.

mode  Main:subrun   (default = -999; minimum = 0)
The number of the current subrun, a non-negative integer, put as first line in a section of lines to be read for this particular subrun.

flag  Main:LHEFskipInit   (default = off)
If you read several Les Houches Event Files that you want to see considered as one single combined event sample you can set this flag on after the first subrun to skip (most of) the (re-)initialization step.

mode  Main:numberOfSubruns   (default = 0)
The number of subruns you intend to use in your current run. Unlike the two settings above, Pythia itself will not intepret this number, but you could e.g. have a loop in your main program to loop over subruns from 0 through numberOfSubruns - 1.

Spares

For currently unforeseen purposes, a few dummy settings are made available here. The user can set the desired value in a "cards file" and then use that value in the main program as desired.

flag  Main:spareFlag1   (default = off)

flag  Main:spareFlag2   (default = off)

flag  Main:spareFlag3   (default = off)

mode  Main:spareMode1   (default = 0)

mode  Main:spareMode2   (default = 0)

mode  Main:spareMode3   (default = 0)

parm  Main:spareParm1   (default = 0.)

parm  Main:spareParm2   (default = 0.)

parm  Main:spareParm3   (default = 0.)

word  Main:spareWord1   (default = void)

word  Main:spareWord2   (default = void)

word  Main:spareWord3   (default = void)