+++ /dev/null
-<chapter name="Event Statistics">
-
-<h2>Event Statistics</h2>
-
-At the end of the run you will want to write out the final statistics
-on number of events generated, the corresponding cross sections and
-the number of errors encountered. This is done either with the
-<code>pythia.stat()</code> method or the <code>pythia.statistics()</code>
-one, assuming <code>pythia</code> is an instance of the
-<code>Pythia</code> class.The former method is steered entirely by
-settings values, see <aloc href="MainProgramSettings">here</aloc>.
-The latter, deprecated one instead takes two arguments:
-
-<method name="void Pythia::statistics(bool all = false, bool reset = false)">
-write out statistics on cross sections and errors. This is based on
-calls to the methods below, for the two kinds of information.
-<argument name="all">
-if <code>true</code> it allows a more extensive listing than the default
-one, see multiparton-interactions statistics below.
-</argument>
-<argument name="reset"> if <code>true</code> it implies that all counters,
-e.g on events generated and errors experienced, are reset to zero whenever
-the routine is called. The default instead is that all stored
-statistics information is unaffected by the call.
-Counters are automatically reset in each new <code>Pythia::init()</code>
-call, however, so the only time the <code>reset</code> option makes a
-difference is if <code>statistics(...)</code> is called several times
-in a (sub)run.
-</argument>
-</method>
-
-<h3>Cross-section statistics</h3>
-
-The <code>ProcessLevel::statistics()</code> method cannot be accessed
-directly, but only via the <code>Pythia::stat()</code> and
-<code>Pythia::statistics(...)</code> calls above.
-When called it will loop over the list of existing processes, and for
-each write out name, code, the number of tried, selected and accepted
-events, the cross section and the estimated error on the latter.
-The three different event numbers are related to the Monte Carlo method
-used, whereby an initial upper estimate of the cross section is used to
-select a large number of trial phase-space points, whereof then not all
-survive. Rejections are normally done by the internal machinery, but can
-also be obtained by <aloc href="UserHooks">user hooks</aloc>.
-Therefore:
-<ul>
-<li><b>tried</b> events reflect the original number of
-phase-space points probed, as part of the upper estimate;</li>
-<li><b>selected</b> events correspond to those that survive
-the internal Monte-Carlo selection procedure;</li>
-<li><b>accepted</b> events are those that also survive
-the additional user cuts.</li>
-</ul>
-In most runs there would be no user hooks implemented, and then the
-numbers of selected and of accepted events will agree. Aborted events
-(see below) usually appear in the selected statistics but not in the
-accepted one.
-
-<p/>
-For Les Houches events the total cross section will be correctly
-displayed; however the (optional) error value will not be used, so that
-the reported error will be smaller than the correct statistical ones,
-and often vanish completely. Furthermore, while the number of events
-is shown for each user process, the cross section is only for the sum
-of them.
-
-<h3>Error messages</h3>
-
-When Pythia is run, errors may occur, and give rise to warning messages.
-These may be of varying severity, as follows:
-<ul>
-<li><b>Abort</b> means things went seriously wrong, and the
-initialization or event generation failed. In the former case it is
-not possible to generate events at all, in the latter the current
-event is flawed and should be skipped. In either case the respective
-method, <code>Pythia::init()</code> or <code>Pythia::next()</code>,
-then also returns the value <code>false</code>. There are occasions
-where an abort may be deliberate, such as when a file of Les Houches
-Events is read and the end of the file is reached.</li>
-<li><b>Error</b> normally is less severe. Typically the program will
-back up one step and try again. There are cases where this is not possible,
-in particular during the initialization and the generation of a hard
-process, and then the error may be followed by an abort as a direct
-consequence (with two separate messages).</li>
-<li><b>Warning</b> is even less severe. In some cases the program will
-try again, with good chances of success, in others no measure at all
-need to be taken.</li>
-</ul>
-
-<p/>
-The error messages is handled by a small part of the <code>Info</code>
-class. It is handed any abort, error or warning messages during the event
-generation phase, and will store each distinct message, with a counter
-for how many times it is issued. Thus it is possible to limit the number
-of identical messages issued, currently hardcoded so that each kind of
-error message is only printed once
-(<code>static const int TIMESTOPRINT = 1</code>).
-This can be overridden by the calling routine, so that all messages of
-this kind are shown, which is particularly relevant for the
-initialization stage.
-The summary table printed by <code>Pythia::statistics()</code>
-provides a table with all the different messages issued, in
-alphabetical order, with the total number of times each was generated.
-
-<h3>Multiparton-interactions statistics</h3>
-
-If you call <code>Pythia::statistics(true)</code>, i.e. with the first
-optional argument <code>true</code>, also statistics on multiparton
-interactions is printed, comprising a list of all allowed subprocesses
-with how many times each of them has been generated. For the minimum-bias
-process this also includes the hardest interaction, while else the
-hardest process is excluded from the statistics. (This is because
-the hardest process is of the same character and generated by the same
-machinery in the former case but not in the latter. Also, for the
-former case only, the standard statistics listing only lists
-minimum bias as one single process, i.e. does not further specify
-the character of the hardest subprocess, so there is not any overlap
-between the two.)
-
-</chapter>
-
-<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
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