Make sure named bins are unique in HLTObjectsMonitor

In the newest version of ROOT, histograms with named bins are
merged via the bin's name, not the index. This means we must
avoid bins having the same bin names.
HLTObjectsMonitor has a histogram which uses path names for the
bin names. In the past, multiple bins could have the same path
name. This change guarantees uniqueness for the bin names and
only fills a bin once per event.

DQM/HLTEvF/plugins/HLTObjectsMonitor.cc

@@ -2,6 +2,8 @@
 #include <memory>
 #include <sys/time.h>
 #include <cstdlib>
+#include <unordered_set>
+#include <unordered_map>
 
 // user include files
 #include "DataFormats/Common/interface/TriggerResults.h"
@@ -37,7 +39,6 @@
 
 #include "TLorentzVector.h"
 
-#include <unordered_map>
 
 
 struct hltPlot {
@@ -127,6 +128,7 @@ class HLTObjectsMonitor : public DQMEDAnalyzer {
 
   MonitorElement* eventsPlot_;
   std::vector<hltPlot> hltPlots_;
+  std::unordered_map<std::string, int> plotNamesToBins_;
 
   bool debug_;
 
@@ -345,15 +347,20 @@ HLTObjectsMonitor::analyze(const edm::Event& iEvent, const edm::EventSetup& iSet
 
   // loop over path
   int ibin = -1;
+  std::unordered_set<int> plottedPathNameIndices;
   for (auto & plot : hltPlots_) {
     ibin++;
     if ( plot.pathIDX <= 0 ) continue;
 
     if ( triggerResults->accept(plot.pathIDX) ) {
-      if ( debug_ )
-	std::cout << plot.pathNAME << " --> bin: " << ibin << std::endl;
-      eventsPlot_->Fill(ibin);
-
+      //We only want to fill this once per pathNAME per event
+      auto index = plotNamesToBins_[plot.pathNAME];
+      if(plottedPathNameIndices.end() == plottedPathNameIndices.find(index)) {
+        plottedPathNameIndices.insert(index);
+        if ( debug_ )
+          std::cout << plot.pathNAME << " --> bin: " << ibin << std::endl;
+        eventsPlot_->Fill(index);
+      }
       const trigger::TriggerObjectCollection objects = triggerEvent->getObjects();
       if ( hltConfig_.saveTags(plot.moduleNAME) ) {
 	if ( debug_ )
@@ -591,13 +598,27 @@ void HLTObjectsMonitor::bookHistograms(DQMStore::IBooker & ibooker, edm::Run con
 
   std::string name  = "eventsPerPath_"+label_;
   std::string title = " events per path";
-  int nbins = hltPlots_.size();
-  eventsPlot_ = ibooker.book1D(name,title,nbins,-0.5,double(nbins)-0.5);
-  eventsPlot_->setAxisTitle("HLT path");
-  for ( int i=0; i<nbins; i++ ) {
-    eventsPlot_->setBinLabel(i+1,hltPlots_[i].pathNAME);
-    if ( debug_ )
-      std::cout << hltPlots_[i].pathNAME << " --> bin: " << i+1 << std::endl;
+
+  //We must avoid repeating the same pathNAME
+  {
+    std::unordered_map<std::string,int> uniqueNames;
+    for(auto const& p: hltPlots_) {
+      plotNamesToBins_[p.pathNAME] = -1;
+    }
+    int nbins = plotNamesToBins_.size();
+    eventsPlot_ = ibooker.book1D(name,title,nbins,-0.5,double(nbins)-0.5);
+    eventsPlot_->setAxisTitle("HLT path");
+    int i=0;
+    //keep the bin order the same as hltPlots_
+    for (auto const& p :  hltPlots_) {
+      //only add a bin if this is the first time we've seen the name
+      if( -1 == plotNamesToBins_[p.pathNAME]) {
+        plotNamesToBins_[p.pathNAME] = i;
+        eventsPlot_->setBinLabel(i,p.pathNAME);
+        if ( debug_ )
+          std::cout << p.pathNAME << " --> bin: " << i << std::endl;
+      }
+    }
   }
 
   for (auto & plot : hltPlots_) {