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source: git/external/fastjet/plugins/CMSIterativeCone/SortByEt.h@ b99c90b

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Last change on this file since b99c90b was d7d2da3, checked in by pavel <pavel@…>, 12 years ago

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1#ifndef __CMS_ITERATIVE_CONE__SORT_BY_ET_H__
2#define __CMS_ITERATIVE_CONE__SORT_BY_ET_H__
3
4//STARTHEADER
5// $Id$
6//
7// Copyright (c) ????-????, CMS collaboration
8// Copyright (c) 2009-2011, Matteo Cacciari, Gavin P. Salam and Gregory Soyez [for the changes listed below]
9//
10//----------------------------------------------------------------------
11// This file distributed with FastJet has been obtained from the CMS
12// collaboration, revision 1.2 of the EtComparator.h file in CMSSW,
13// see
14// http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/CMSSW/PhysicsTools/Utilities/interface/EtComparator.h?hideattic=0&revision=1.2&view=markup
15//
16// Permission has been granted by the CMS collaboration to release it
17// in FastJet under the terms of the GNU Public License(v2) (see the
18// COPYING file in the main FastJet directory for details).
19// Changes from the original file are listed below.
20//
21// FastJet is free software; you can redistribute it and/or modify
22// it under the terms of the GNU General Public License as published by
23// the Free Software Foundation; either version 2 of the License, or
24// (at your option) any later version.
25//
26// The algorithms that underlie FastJet have required considerable
27// development and are described in hep-ph/0512210. If you use
28// FastJet as part of work towards a scientific publication, please
29// include a citation to the FastJet paper.
30//
31// FastJet is distributed in the hope that it will be useful,
32// but WITHOUT ANY WARRANTY; without even the implied warranty of
33// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
34// GNU General Public License for more details.
35//
36// You should have received a copy of the GNU General Public License
37// along with FastJet. If not, see <http://www.gnu.org/licenses/>.
38//----------------------------------------------------------------------
39//ENDHEADER
40
41// List of changes compared to the original CMS code (revision 1.2 of
42// EtComparator.h)
43//
44// 2009-01-06 Gregory Soyez <soyez@fastjet.fr>
45//
46// * Extracted (only) NumericSafeGreaterByEt from the CMS code
47// and adapted it to act on PseudoJet rather than CMS types
48// for 4-momenta
49// * Put the code in a fastjet::cms namespace
50
51#include <limits>
52#include <fastjet/internal/base.hh>
53
54FASTJET_BEGIN_NAMESPACE
55
56namespace cms{
57
58template <class T>
59struct NumericSafeGreaterByEt {
60 typedef T first_argument_type;
61 typedef T second_argument_type;
62 bool operator()(const T& a1, const T& a2) {
63 // FastJet::PseudoJet does not provide a direct access to Et2
64 // Plus, we want it to be computed in the same way as in the CMS
65 // code (actually the Root code that is used by CMS)
66 double et1 = a1.Et();
67 double et2 = a2.Et();
68
69 // now we can come back to the CMS code
70 return
71 fabs (et1-et2) > std::numeric_limits<double>::epsilon() ? et1 > et2 :
72 fabs (a1.px()-a2.px()) > std::numeric_limits<double>::epsilon() ? a1.px() > a2.px() :
73 a1.pz() > a2.pz();
74 }
75};
76
77} // namespace cms
78
79FASTJET_END_NAMESPACE
80
81
82#endif // __CMS_ITERATIVE_CONE__SORT_BY_ET_H__
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