Optionally drop huge clusters in the ALPIDE clusterer (#13808)

Author: mconcas

Detectors/ITSMFT/ITS/workflow/src/ClustererSpec.cxx

@@ -121,8 +121,9 @@ void ClustererDPL::updateTimeDependentParams(ProcessingContext& pc)
     // settings for the fired pixel overflow masking
     const auto& alpParams = o2::itsmft::DPLAlpideParam<o2::detectors::DetID::ITS>::Instance();
     const auto& clParams = o2::itsmft::ClustererParam<o2::detectors::DetID::ITS>::Instance();
+    mClusterer->setDropHugeClusters(clParams.dropHugeClusters);
     if (clParams.maxBCDiffToMaskBias > 0 && clParams.maxBCDiffToSquashBias > 0) {
-      LOGP(fatal, "maxBCDiffToMaskBias = {} and maxBCDiffToMaskBias = {} cannot be set at the same time. Either set masking or squashing with a BCDiff > 0", clParams.maxBCDiffToMaskBias, clParams.maxBCDiffToSquashBias);
+      LOGP(fatal, "maxBCDiffToMaskBias = {} and maxBCDiffToSquashBias = {} cannot be set at the same time. Either set masking or squashing with a BCDiff > 0", clParams.maxBCDiffToMaskBias, clParams.maxBCDiffToSquashBias);
     }
     auto nbc = clParams.maxBCDiffToMaskBias;
     nbc += mClusterer->isContinuousReadOut() ? alpParams.roFrameLengthInBC : (alpParams.roFrameLengthTrig / o2::constants::lhc::LHCBunchSpacingNS);

Detectors/ITSMFT/MFT/workflow/src/ClustererSpec.cxx

@@ -122,8 +122,9 @@ void ClustererDPL::updateTimeDependentParams(ProcessingContext& pc)
     const auto& alpParams = o2::itsmft::DPLAlpideParam<o2::detectors::DetID::MFT>::Instance();
     const auto& clParams = o2::itsmft::ClustererParam<o2::detectors::DetID::MFT>::Instance();
     if (clParams.maxBCDiffToMaskBias > 0 && clParams.maxBCDiffToSquashBias > 0) {
-      LOGP(fatal, "maxBCDiffToMaskBias = {} and maxBCDiffToMaskBias = {} cannot be set at the same time. Either set masking or squashing with a BCDiff > 0", clParams.maxBCDiffToMaskBias, clParams.maxBCDiffToSquashBias);
+      LOGP(fatal, "maxBCDiffToMaskBias = {} and maxBCDiffToSquashBias = {} cannot be set at the same time. Either set masking or squashing with a BCDiff > 0", clParams.maxBCDiffToMaskBias, clParams.maxBCDiffToSquashBias);
     }
+    mClusterer->setDropHugeClusters(clParams.dropHugeClusters);
     auto nbc = clParams.maxBCDiffToMaskBias;
     nbc += mClusterer->isContinuousReadOut() ? alpParams.roFrameLengthInBC : (alpParams.roFrameLengthTrig / o2::constants::lhc::LHCBunchSpacingNS);
     mClusterer->setMaxBCSeparationToMask(nbc);

Detectors/ITSMFT/common/reconstruction/include/ITSMFTReconstruction/Clusterer.h

@@ -204,6 +204,9 @@ class Clusterer
   bool isContinuousReadOut() const { return mContinuousReadout; }
   void setContinuousReadOut(bool v) { mContinuousReadout = v; }
 
+  bool isDropHugeClusters() const { return mDropHugeClusters; }
+  void setDropHugeClusters(bool v) { mDropHugeClusters = v; }
+
   int getMaxBCSeparationToMask() const { return mMaxBCSeparationToMask; }
   void setMaxBCSeparationToMask(int n) { mMaxBCSeparationToMask = n; }
 
@@ -238,6 +241,7 @@ class Clusterer
 
   // clusterization options
   bool mContinuousReadout = true; ///< flag continuous readout
+  bool mDropHugeClusters = false; ///< don't include clusters that would be split in more than one
 
   ///< mask continuosly fired pixels in frames separated by less than this amount of BCs (fired from hit in prev. ROF)
   int mMaxBCSeparationToMask = 6000. / o2::constants::lhc::LHCBunchSpacingNS + 10;

Detectors/ITSMFT/common/reconstruction/include/ITSMFTReconstruction/ClustererParam.h

@@ -38,6 +38,7 @@ struct ClustererParam : public o2::conf::ConfigurableParamHelper<ClustererParam<
   int maxBCDiffToMaskBias = 10;                    ///< mask if 2 ROFs differ by <= StrobeLength + Bias BCs, use value <0 to disable masking
   int maxBCDiffToSquashBias = -10;                 ///< squash if 2 ROFs differ by <= StrobeLength + Bias BCs, use value <0 to disable squashing
   float maxSOTMUS = 8.;                            ///< max expected signal over threshold in \mus
+  bool dropHugeClusters = false;                   ///< option to drop huge clusters (mitigate beam background)
 
   O2ParamDef(ClustererParam, getParamName().data());
 

Detectors/ITSMFT/common/reconstruction/src/Clusterer.cxx

@@ -263,36 +263,38 @@ void Clusterer::ClustererThread::finishChip(ChipPixelData* curChipData, CompClus
       parent->streamCluster(pixArrBuff, &labelsBuff, bbox, parent->mPattIdConverter, compClusPtr, patternsPtr, labelsClusPtr, nlab);
     } else {
       auto warnLeft = MaxHugeClusWarn - parent->mNHugeClus;
-      if (warnLeft > 0) {
-        LOGP(warn, "Splitting a huge cluster: chipID {}, rows {}:{} cols {}:{}{}", bbox.chipID, bbox.rowMin, bbox.rowMax, bbox.colMin, bbox.colMax,
-             warnLeft == 1 ? " (Further warnings will be muted)" : "");
+      if (!parent->mDropHugeClusters) {
+        if (warnLeft > 0) {
+          LOGP(warn, "Splitting a huge cluster: chipID {}, rows {}:{} cols {}:{}{}", bbox.chipID, bbox.rowMin, bbox.rowMax, bbox.colMin, bbox.colMax,
+               warnLeft == 1 ? " (Further warnings will be muted)" : "");
 #ifdef WITH_OPENMP
 #pragma omp critical
 #endif
-        {
-          parent->mNHugeClus++;
+          {
+            parent->mNHugeClus++;
+          }
         }
-      }
-      BBox bboxT(bbox); // truncated box
-      std::vector<PixelData> pixbuf;
-      do {
-        bboxT.rowMin = bbox.rowMin;
-        bboxT.colMax = std::min(bbox.colMax, uint16_t(bboxT.colMin + o2::itsmft::ClusterPattern::MaxColSpan - 1));
-        do { // Select a subset of pixels fitting the reduced bounding box
-          bboxT.rowMax = std::min(bbox.rowMax, uint16_t(bboxT.rowMin + o2::itsmft::ClusterPattern::MaxRowSpan - 1));
-          for (const auto& pix : pixArrBuff) {
-            if (bboxT.isInside(pix.getRowDirect(), pix.getCol())) {
-              pixbuf.push_back(pix);
+        BBox bboxT(bbox); // truncated box
+        std::vector<PixelData> pixbuf;
+        do {
+          bboxT.rowMin = bbox.rowMin;
+          bboxT.colMax = std::min(bbox.colMax, uint16_t(bboxT.colMin + o2::itsmft::ClusterPattern::MaxColSpan - 1));
+          do { // Select a subset of pixels fitting the reduced bounding box
+            bboxT.rowMax = std::min(bbox.rowMax, uint16_t(bboxT.rowMin + o2::itsmft::ClusterPattern::MaxRowSpan - 1));
+            for (const auto& pix : pixArrBuff) {
+              if (bboxT.isInside(pix.getRowDirect(), pix.getCol())) {
+                pixbuf.push_back(pix);
+              }
             }
-          }
-          if (!pixbuf.empty()) { // Stream a piece of cluster only if the reduced bounding box is not empty
-            parent->streamCluster(pixbuf, &labelsBuff, bboxT, parent->mPattIdConverter, compClusPtr, patternsPtr, labelsClusPtr, nlab, true);
-            pixbuf.clear();
-          }
-          bboxT.rowMin = bboxT.rowMax + 1;
-        } while (bboxT.rowMin < bbox.rowMax);
-        bboxT.colMin = bboxT.colMax + 1;
-      } while (bboxT.colMin < bbox.colMax);
+            if (!pixbuf.empty()) { // Stream a piece of cluster only if the reduced bounding box is not empty
+              parent->streamCluster(pixbuf, &labelsBuff, bboxT, parent->mPattIdConverter, compClusPtr, patternsPtr, labelsClusPtr, nlab, true);
+              pixbuf.clear();
+            }
+            bboxT.rowMin = bboxT.rowMax + 1;
+          } while (bboxT.rowMin < bbox.rowMax);
+          bboxT.colMin = bboxT.colMax + 1;
+        } while (bboxT.colMin < bbox.colMax);
+      }
     }
   }
 }
@@ -451,8 +453,8 @@ void Clusterer::print() const
 {
   // print settings
   LOGP(info, "Clusterizer squashes overflow pixels separated by {} BC and <= {} in row/col seeking down to {} neighbour ROFs", mMaxBCSeparationToSquash, mMaxRowColDiffToMask, mSquashingDepth);
-  LOG(info) << "Clusterizer masks overflow pixels separated by < " << mMaxBCSeparationToMask << " BC and <= "
-            << mMaxRowColDiffToMask << " in row/col";
+  LOGP(info, "Clusterizer masks overflow pixels separated by < {} BC and <= {} in row/col", mMaxBCSeparationToMask, mMaxRowColDiffToMask);
+  LOGP(info, "Clusterizer does {} drop huge clusters", mDropHugeClusters ? "" : "not");
 
 #ifdef _PERFORM_TIMING_
   auto& tmr = const_cast<TStopwatch&>(mTimer); // ugly but this is what root does internally