[Common] CTP: avoid useless work to count non-zero bits (#16400)

Author: ktf

Common/CCDB/ctpRateFetcher.cxx

@@ -95,9 +95,7 @@ double ctpRateFetcher::pileUpCorrection(double triggerRate)
   if (mLHCIFdata == nullptr) {
     LOG(fatal) << "No filling" << std::endl;
   }
-  auto bfilling = mLHCIFdata->getBunchFilling();
-  std::vector<int> bcs = bfilling.getFilledBCs();
-  double nbc = bcs.size();
+  double nbc = mLHCIFdata->getBunchFilling().getPattern().count();
   double nTriggersPerFilledBC = triggerRate / nbc / constants::lhc::LHCRevFreq;
   double mu = -std::log(1 - nTriggersPerFilledBC);
   return mu * nbc * constants::lhc::LHCRevFreq;