[EMCAL-685] Implementation of a ring buffer for EMCAL digits

Author: hahassan7

Detectors/EMCAL/simulation/CMakeLists.txt

@@ -10,14 +10,15 @@
 
 o2_add_library(EMCALSimulation
                SOURCES src/Detector.cxx src/Digitizer.cxx src/DigitizerTask.cxx
-                       src/SpaceFrame.cxx src/SimParam.cxx src/LabeledDigit.cxx
-                       src/RawWriter.cxx
+                       src/DigitsWriteoutBuffer.cxx src/SpaceFrame.cxx src/SimParam.cxx
+                       src/LabeledDigit.cxx src/RawWriter.cxx
                PUBLIC_LINK_LIBRARIES O2::EMCALBase O2::DetectorsBase O2::SimConfig O2::SimulationDataFormat O2::Headers O2::DetectorsRaw)
 
 o2_target_root_dictionary(EMCALSimulation
                           HEADERS include/EMCALSimulation/Detector.h
                                   include/EMCALSimulation/Digitizer.h
                                   include/EMCALSimulation/DigitizerTask.h
+                                  include/EMCALSimulation/DigitsWriteoutBuffer.h
                                   include/EMCALSimulation/RawWriter.h
                                   include/EMCALSimulation/SpaceFrame.h
                                   include/EMCALSimulation/SimParam.h

Detectors/EMCAL/simulation/include/EMCALSimulation/DigitsWriteoutBuffer.h

@@ -0,0 +1,84 @@
+// Copyright CERN and copyright holders of ALICE O2. This software is
+// distributed under the terms of the GNU General Public License v3 (GPL
+// Version 3), copied verbatim in the file "COPYING".
+//
+// See http://alice-o2.web.cern.ch/license for full licensing information.
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+#ifndef ALICEO2_EMCAL_DIGITSWRITEOUTBUFFER_H_
+#define ALICEO2_EMCAL_DIGITSWRITEOUTBUFFER_H_
+
+#include <memory>
+#include <unordered_map>
+#include <vector>
+#include <deque>
+#include "DataFormatsEMCAL/Digit.h"
+#include "EMCALSimulation/LabeledDigit.h"
+
+namespace o2
+{
+namespace emcal
+{
+
+/// \class DigitsWriteoutBuffer
+/// \brief Container class for time sampled digits
+/// \ingroup EMCALsimulation
+/// \author Hadi Hassan, ORNL
+/// \author Markus Fasel, ORNL
+/// \date 08/03/2021
+
+class DigitsWriteoutBuffer
+{
+ public:
+  /// Default constructor
+  DigitsWriteoutBuffer(unsigned int nTimeBins = 30, unsigned int binWidth = 100);
+
+  /// Destructor
+  ~DigitsWriteoutBuffer() = default;
+
+  /// Reset the container
+  void reset();
+
+  /// Add digit to the container
+  /// \param towerID Cell ID
+  /// \param dig Labaled digit to add
+  /// \param eventTime The time of the event (w.r.t Tigger time)
+  void addDigit(unsigned int towerID, LabeledDigit dig, double eventTime);
+
+  /// Getter for the last N entries (time samples) in the ring buffer
+  /// \param nsample number of entries to be written
+  /// \return Vector of map of cell IDs and labeled digits in that cell
+  gsl::span<std::unordered_map<int, LabeledDigit>> getLastNSamples(int nsample = 15);
+
+  /// Forwards the marker to the next time sample every mTimeBinWidth
+  void forwardMarker(double eventTime);
+
+  void setNumberReadoutSamples(unsigned int nsamples) { mNumberReadoutSamples = nsamples; }
+
+  /// Getter for current position in the ring buffer
+  /// \return current position
+  std::tuple<double, int> getCurrentTimeAndPosition() const { return std::make_tuple(mMarker.mReferenceTime, mMarker.mPositionInBuffer - mTimedDigits.begin()); }
+
+ private:
+  struct Marker {
+    double mReferenceTime;
+    std::deque<std::unordered_map<int, LabeledDigit>>::iterator mPositionInBuffer;
+  };
+
+  unsigned int mBufferSize = 30;                                  ///< The size of the buffer, it has to be at least 2 times the size of the readout cycle
+  unsigned int mTimeBinWidth = 100;                               ///< The size of the time bin (ns)
+  unsigned int mNumberReadoutSamples = 15;                        ///< The number of smaples in a readout window
+  Marker mMarker;                                                 ///< Marker for the current time sample
+  std::deque<std::unordered_map<int, LabeledDigit>> mTimedDigits; ///< Container for time sampled digits per tower ID
+
+  ClassDefNV(DigitsWriteoutBuffer, 1);
+};
+
+} // namespace emcal
+
+} // namespace o2
+
+#endif /* ALICEO2_EMCAL_DIGITSWRITEOUTBUFFER_H_ */

Detectors/EMCAL/simulation/src/DigitsWriteoutBuffer.cxx

@@ -0,0 +1,61 @@
+// Copyright CERN and copyright holders of ALICE O2. This software is
+// distributed under the terms of the GNU General Public License v3 (GPL
+// Version 3), copied verbatim in the file "COPYING".
+//
+// See http://alice-o2.web.cern.ch/license for full licensing information.
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+#include <unordered_map>
+#include <vector>
+#include <deque>
+#include <gsl/span>
+#include "EMCALSimulation/LabeledDigit.h"
+#include "EMCALSimulation/DigitsWriteoutBuffer.h"
+
+using namespace o2::emcal;
+
+DigitsWriteoutBuffer::DigitsWriteoutBuffer(unsigned int nTimeBins, unsigned int binWidth) : mBufferSize(nTimeBins),
+                                                                                            mTimeBinWidth(binWidth)
+{
+  mTimedDigits.resize(nTimeBins);
+  mMarker.mReferenceTime = 0.;
+  mMarker.mPositionInBuffer = mTimedDigits.begin();
+}
+
+void DigitsWriteoutBuffer::reset()
+{
+  mTimedDigits.clear();
+  mMarker.mReferenceTime = 0.;
+  mMarker.mPositionInBuffer = mTimedDigits.begin();
+}
+
+void DigitsWriteoutBuffer::addDigit(unsigned int towerID, LabeledDigit dig, double eventTime)
+{
+
+  int nsamples = int((eventTime - mMarker.mReferenceTime) / mTimeBinWidth);
+  auto timeEntry = mMarker.mPositionInBuffer + nsamples;
+  timeEntry->insert(std::make_pair(towerID, dig));
+}
+
+void DigitsWriteoutBuffer::forwardMarker(double eventTime)
+{
+  mMarker.mReferenceTime = eventTime;
+  mMarker.mPositionInBuffer++;
+
+  // Allocate new memory at the end
+  mTimedDigits.push_back(std::unordered_map<int, LabeledDigit>());
+
+  // Drop entry at the front, because it is outside the current readout window
+  // only done if we have at least 15 entries
+  if (mMarker.mPositionInBuffer - mTimedDigits.begin() > mNumberReadoutSamples) {
+    mTimedDigits.pop_front();
+  }
+}
+
+gsl::span<std::unordered_map<int, LabeledDigit>> DigitsWriteoutBuffer::getLastNSamples(int nsamples)
+{
+  return gsl::span<std::unordered_map<int, LabeledDigit>>(&mTimedDigits[int(mMarker.mPositionInBuffer - mTimedDigits.begin() - nsamples)], nsamples);
+}

Detectors/EMCAL/simulation/src/EMCALSimulationLinkDef.h

@@ -18,6 +18,7 @@
 #pragma link C++ class o2::base::DetImpl < o2::emcal::Detector> + ;
 #pragma link C++ class o2::emcal::Digitizer + ;
 #pragma link C++ class o2::emcal::DigitizerTask + ;
+#pragma link C++ class o2::emcal::DigitsWriteoutBuffer + ;
 #pragma link C++ class o2::emcal::SimParam + ;
 #pragma link C++ class o2::emcal::LabeledDigit + ;
 #pragma link C++ class o2::emcal::RawWriter + ;