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FastJet 3.0alpha3
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FastJet 3.0alpha3
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Implementation of the spherical version of the SISCone algorithm (plugin for fastjet v2.1 upwards) More...
#include <SISConeSphericalPlugin.hh>
Inherits fastjet::SISConeBasePlugin.
Public Types | |
| enum | SplitMergeScale { SM_E, SM_Etilde } |
| enum for the different split-merge scale choices; Note that order _must_ be the same as in siscone More... | |
Public Member Functions | |
| SISConeSphericalPlugin (double cone_radius, double overlap_threshold, int n_pass_max=0, double protojet_Emin=0.0, bool caching=false, SplitMergeScale split_merge_scale=SM_Etilde, double split_merge_stopping_scale=0.0) | |
| Main constructor for the SISConeSpherical Plugin class. | |
| double | protojet_Emin () const |
| minimum energy for a protojet to be considered in the split-merge step of the algorithm | |
| double | protojet_or_ghost_Emin () const |
| return the scale to be passed to SISCone as the protojet_Emin | |
| SplitMergeScale | split_merge_scale () const |
| indicates scale used in split-merge | |
| void | set_split_merge_scale (SplitMergeScale sms) |
| sets scale used in split-merge | |
| bool | split_merge_use_E_weighted_splitting () const |
| indicate if the splittings are done using the anti-kt distance | |
| void | set_split_merge_use_E_weighted_splitting (bool val) |
| virtual bool | supports_ghosted_passive_areas () const |
| overload the default as we don't provide support for passive areas. | |
| virtual std::string | description () const |
| return a textual description of the jet-definition implemented in this plugin | |
| virtual void | run_clustering (ClusterSequence &) const |
| given a ClusterSequence that has been filled up with initial particles, the following function should fill up the rest of the ClusterSequence, using the following member functions of ClusterSequence: | |
Protected Member Functions | |
| virtual void | reset_stored_plugin () const |
Implementation of the spherical version of the SISCone algorithm (plugin for fastjet v2.1 upwards)
SISConeSphericalPlugin is a plugin for fastjet (v2.1 upwards) that provides an interface to the seedless infrared safe cone jet finder by Gregory Soyez and Gavin Salam.
This is the version of SISCone using spherical coordinates. Compared to the original cylindrical version:
For moderate values of R the problem should not be too severe (or may even be absent for some values of the overlap parameter), however the user should be aware of the issue.
The default split-merge scale may change at a later date to resolve this issue.
SISCone uses geometrical techniques to exhaustively consider all possible distinct cones. It then finds out which ones are stable and sends the result to the Tevatron Run-II type split-merge procedure for overlapping cones.
Four parameters govern the "physics" of the algorithm:
One parameter governs some internal algorithmic shortcuts:
The final jets can be accessed by requestion the inclusive_jets(...) from the ClusterSequence object. Note that these PseudoJets have their user_index() set to the index of the pass in which they were found (first pass = 0). NB: This does not currently work for jets that consist of a single particle.
For further information on the details of the algorithm see the SISCone paper, arXiv:0704.0292 [JHEP 0705:086,2007].
For documentation about the implementation, see the siscone/doc/html/index.html file.
Definition at line 94 of file SISConeSphericalPlugin.hh.
enum for the different split-merge scale choices; Note that order _must_ be the same as in siscone
| SM_E |
Energy (IR unsafe with momentum conservation) |
| SM_Etilde |
sum_{i jet} E_i [1+sin^2(theta_iJ)] |
Definition at line 99 of file SISConeSphericalPlugin.hh.
| double fastjet::SISConeSphericalPlugin::protojet_or_ghost_Emin | ( | ) | const [inline] |
return the scale to be passed to SISCone as the protojet_Emin
-- if we have a ghost separation scale that is above the protojet_ptmin, then the ghost_separation_scale becomes the relevant one to use here
Definition at line 133 of file SISConeSphericalPlugin.hh.
{return std::max(_protojet_Emin,
_ghost_sep_scale);}
| virtual bool fastjet::SISConeSphericalPlugin::supports_ghosted_passive_areas | ( | ) | const [inline, virtual] |
overload the default as we don't provide support for passive areas.
Reimplemented from fastjet::JetDefinition::Plugin.
Definition at line 148 of file SISConeSphericalPlugin.hh.
{return true;}
| void fastjet::SISConeSphericalPlugin::run_clustering | ( | ClusterSequence & | ) | const [virtual] |
given a ClusterSequence that has been filled up with initial particles, the following function should fill up the rest of the ClusterSequence, using the following member functions of ClusterSequence:
Implements fastjet::JetDefinition::Plugin.
Definition at line 75 of file SISConeSphericalPlugin.cc.
References fastjet::have_same_momentum(), fastjet::ClusterSequence::jets(), fastjet::ClusterSequence::plugin_associate_extras(), fastjet::ClusterSequence::plugin_record_iB_recombination(), fastjet::ClusterSequence::plugin_record_ij_recombination(), and fastjet::PseudoJet::set_user_index().
{
CSphsiscone local_siscone;
CSphsiscone * siscone;
unsigned n = clust_seq.jets().size();
bool new_siscone = true; // by default we'll be running it
if (caching()) {
// Establish if we have a cached run with the same R, npass and
// particles. If not then do any tidying up / reallocation that's
// necessary for the next round of caching, otherwise just set
// relevant pointers so that we can reuse and old run.
if (stored_siscone.get() != 0) {
new_siscone = !(stored_plugin->cone_radius() == cone_radius()
&& stored_plugin->n_pass_max() == n_pass_max()
&& stored_particles->size() == n);
if (!new_siscone) {
for(unsigned i = 0; i < n; i++) {
// only check momentum because indices will be correctly dealt
// with anyway when extracting the clustering order.
new_siscone |= !have_same_momentum(clust_seq.jets()[i],
(*stored_particles)[i]);
}
}
}
// allocate the new siscone, etc., if need be
if (new_siscone) {
stored_siscone .reset( new CSphsiscone );
stored_particles.reset( new std::vector<PseudoJet>(clust_seq.jets()));
reset_stored_plugin();
}
siscone = stored_siscone.get();
} else {
siscone = &local_siscone;
}
// make sure stopping scale is set in siscone
siscone->SM_var2_hardest_cut_off = _split_merge_stopping_scale*_split_merge_stopping_scale;
// set the specific parameters
// when running with ghosts for passive areas, do not put the
// ghosts into the stable-cone search (not relevant)
siscone->stable_cone_soft_E2_cutoff = ghost_separation_scale()
* ghost_separation_scale();
// set the type of splitting we want (default=std one, true->pt-weighted split)
siscone->set_E_weighted_splitting(_use_E_weighted_splitting);
if (new_siscone) {
// transfer fastjet initial particles into the siscone type
std::vector<CSphmomentum> siscone_momenta(n);
for(unsigned i = 0; i < n; i++) {
const PseudoJet & p = clust_seq.jets()[i]; // shorthand
siscone_momenta[i] = CSphmomentum(p.px(), p.py(), p.pz(), p.E());
}
// run the jet finding
//cout << "plg sms: " << split_merge_scale() << endl;
siscone->compute_jets(siscone_momenta, cone_radius(), overlap_threshold(),
n_pass_max(), protojet_or_ghost_Emin(),
Esplit_merge_scale(split_merge_scale()));
} else {
// rerun the jet finding
// just run the overlap part of the jets.
//cout << "plg rcmp sms: " << split_merge_scale() << endl;
siscone->recompute_jets(overlap_threshold(), protojet_or_ghost_Emin(),
Esplit_merge_scale(split_merge_scale()));
}
// extract the jets [in reverse order -- to get nice ordering in pt at end]
int njet = siscone->jets.size();
// allocate space for the extras object
SISConeSphericalExtras * extras = new SISConeSphericalExtras(n);
for (int ijet = njet-1; ijet >= 0; ijet--) {
const CSphjet & jet = siscone->jets[ijet]; // shorthand
// Successively merge the particles that make up the cone jet
// until we have all particles in it. Start off with the zeroth
// particle.
int jet_k = jet.contents[0];
for (unsigned ipart = 1; ipart < jet.contents.size(); ipart++) {
// take the last result of the merge
int jet_i = jet_k;
// and the next element of the jet
int jet_j = jet.contents[ipart];
// and merge them (with a fake dij)
double dij = 0.0;
if (_use_jet_def_recombiner) {
clust_seq.plugin_record_ij_recombination(jet_i, jet_j, dij, jet_k);
} else {
// create the new jet by hand so that we can adjust its user index
PseudoJet newjet = clust_seq.jets()[jet_i] + clust_seq.jets()[jet_j];
// set the user index to be the pass in which the jet was discovered
newjet.set_user_index(jet.pass);
clust_seq.plugin_record_ij_recombination(jet_i, jet_j, dij, newjet, jet_k);
}
}
// we have merged all the jet's particles into a single object, so now
// "declare" it to be a beam (inclusive) jet.
// [NB: put a sensible looking d_iB just to be nice...]
double d_iB = clust_seq.jets()[jet_k].perp2();
clust_seq.plugin_record_iB_recombination(jet_k, d_iB);
// now record the pass of the jet in the extras object
extras->_pass[clust_seq.jets()[jet_k].cluster_hist_index()] = jet.pass;
}
// now copy the list of protocones into an "extras" objects
for (unsigned ipass = 0; ipass < siscone->protocones_list.size(); ipass++) {
for (unsigned ipc = 0; ipc < siscone->protocones_list[ipass].size(); ipc++) {
PseudoJet protocone(siscone->protocones_list[ipass][ipc]);
protocone.set_user_index(ipass);
extras->_protocones.push_back(protocone);
}
}
extras->_most_ambiguous_split = siscone->most_ambiguous_split;
// tell it what the jet definition was
extras->_jet_def_plugin = this;
// give the extras object to the cluster sequence.
clust_seq.plugin_associate_extras(std::auto_ptr<ClusterSequence::Extras>(extras));
}
1.7.4