Tracker Step Compression Big Fix

Filters/src/CompressDigiMCsCheck_module.cc

@@ -133,8 +133,17 @@ namespace mu2e {
 	  throw cet::exception("CompressDigiMCsCheck") << "Old and new StepPointMC times with offsets applied do not match (StrawDigiMC)" << std::endl;
 	}
 
-	// Loop through all the StepPointMCs in the waveform and check that the trigger step points are the same Ptr
+	// Check for tracker duplicate steps, there are two different cases. What should be happening is something like the following:
+	// We have five StepPointMCs: A, B, C, D, E
+	// StrawDigiMC has seven StepPtrs: HVStepPtr-->A   CalStepPtr-->A  WaveformStepPtrs-->A, B, C, D, E
 	if (_checkTrackerDuplicateSteps) {
+	  // Case 1. In this case we have accidentally treated the HVStepPtr and CalStepPtr as separate and duplicated step A (A' and A'')
+	  //         so we end up with seven StepPointsMCs: A, B, C, D, E, A', A''
+	  //         and the StepPtrs all point to different: HVStepPtr-->A'   CalStepPtr-->A''   WaveformStepPtrs-->A, B, C, D, E
+	  // This will not trigger the exception in Case 2
+	  // If we only access steps through digis then you will get the correct information
+	  // You cannot loop over the StepPointMCCollection however
+	  // Here we check that the HV and Cal StepPtrs also exist in the WaveformStepPtrs
 	  const auto& i_newStepPointMCCal = i_newStrawDigiMC.stepPointMC(StrawEnd::cal);
 	  bool identical_cal_ptr = false;
 	  bool identical_hv_ptr = false;
@@ -149,6 +158,27 @@ namespace mu2e {
 	  if (! (identical_hv_ptr && identical_cal_ptr) ) {
 	    throw cet::exception("CompressDigiMCsCheck") << "Trigger StepPointMCs in StrawDigiMCs are not identical to any StepPointMC in the waveform. This could indicate a duplication of StepPointMCs" << std::endl;
 	  }
+
+	  // Case 2: In this case, we have looped over an StepPointMCCollection with duplicated steps
+	  //         (and have not duplicated things further)
+	  //         StepPointMCs: A, B, C, D, E, A', A''
+	  //         and the waveform will now include the duplicated steps:
+	  //         StrawDigiMC: HVStepPtr-->A', CalStepPtr-->A'', WaveformStepPtrs-->A, B, C, D, E, A', A''
+	  // This will not trigger the exception in Case 1
+	  // Here we check that there are no identical waveform steps
+	  for (const auto& i_stepPointPtr : i_newStrawDigiMC.stepPointMCs()) {
+	    for (const auto& j_stepPointPtr : i_newStrawDigiMC.stepPointMCs()) {
+	      if (i_stepPointPtr == j_stepPointPtr) {
+		continue; // these will obviously match
+	      }
+
+	      if ( (i_stepPointPtr->volumeId() == j_stepPointPtr->volumeId()) &&
+		   (i_stepPointPtr->totalEDep() == j_stepPointPtr->totalEDep())
+		   ) {
+		throw cet::exception("CompressDigiMCsCheck") << "Two StepPointMCs in StrawDigiMC waveform are identical" << std::endl;
+	      }
+	    }
+	  }
 	}
       }
     }