From cf1958a196ec23d19a45f9a1a4365c1023c8e7b6 Mon Sep 17 00:00:00 2001
From: shahoian <ruben.shahoyan@cern.ch>
Date: Tue, 21 Jan 2025 16:04:28 +0100
Subject: [PATCH] Fix GPUTPCGeometry LinearPad2Y/Y2Pad methods, define biased
 ones in GPUTPCCompressionTrackModel

---
 .../DataCompression/GPUTPCCompressionKernels.cxx     |  4 ++--
 .../DataCompression/GPUTPCCompressionTrackModel.h    | 12 ++++++++++++
 .../DataCompression/TPCClusterDecompressionCore.inc  |  6 +++---
 GPU/GPUTracking/DataTypes/GPUTPCGeometry.h           |  8 ++++++++
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/GPU/GPUTracking/DataCompression/GPUTPCCompressionKernels.cxx b/GPU/GPUTracking/DataCompression/GPUTPCCompressionKernels.cxx
index 15888e14eec04..d76b509c67518 100644
--- a/GPU/GPUTracking/DataCompression/GPUTPCCompressionKernels.cxx
+++ b/GPU/GPUTracking/DataCompression/GPUTPCCompressionKernels.cxx
@@ -69,7 +69,7 @@ GPUdii() void GPUTPCCompressionKernels::Thread<GPUTPCCompressionKernels::step0at
       }
       const ClusterNative& GPUrestrict() orgCl = clusters->clusters[hit.slice][hit.row][hit.num - clusters->clusterOffset[hit.slice][hit.row]];
       float x = param.tpcGeometry.Row2X(hit.row);
-      float y = param.tpcGeometry.LinearPad2Y(hit.slice, hit.row, orgCl.getPad());
+      float y = track.LinearPad2Y(hit.slice, orgCl.getPad(), param.tpcGeometry.PadWidth(hit.row), param.tpcGeometry.NPads(hit.row));
       float z = param.tpcGeometry.LinearTime2Z(hit.slice, orgCl.getTime());
       if (nClustersStored) {
         if ((hit.slice < GPUCA_NSLICES) ^ (lastSlice < GPUCA_NSLICES)) {
@@ -115,7 +115,7 @@ GPUdii() void GPUTPCCompressionKernels::Thread<GPUTPCCompressionKernels::step0at
         }
         c.rowDiffA[cidx] = row;
         c.sliceLegDiffA[cidx] = (hit.leg == lastLeg ? 0 : compressor.NSLICES) + slice;
-        float pad = CAMath::Max(0.f, CAMath::Min((float)param.tpcGeometry.NPads(GPUCA_ROW_COUNT - 1), param.tpcGeometry.LinearY2Pad(hit.slice, hit.row, track.Y())));
+        float pad = CAMath::Max(0.f, CAMath::Min((float)param.tpcGeometry.NPads(GPUCA_ROW_COUNT - 1), track.LinearY2Pad(hit.slice, track.Y(), param.tpcGeometry.PadWidth(hit.row), param.tpcGeometry.NPads(hit.row))));
         c.padResA[cidx] = orgCl.padPacked - orgCl.packPad(pad);
         float time = CAMath::Max(0.f, param.tpcGeometry.LinearZ2Time(hit.slice, track.Z() + zOffset));
         c.timeResA[cidx] = (orgCl.getTimePacked() - orgCl.packTime(time)) & 0xFFFFFF;
diff --git a/GPU/GPUTracking/DataCompression/GPUTPCCompressionTrackModel.h b/GPU/GPUTracking/DataCompression/GPUTPCCompressionTrackModel.h
index 8003b388e1a68..662975692dbc8 100644
--- a/GPU/GPUTracking/DataCompression/GPUTPCCompressionTrackModel.h
+++ b/GPU/GPUTracking/DataCompression/GPUTPCCompressionTrackModel.h
@@ -100,6 +100,18 @@ class GPUTPCCompressionTrackModel
   GPUd() void getClusterErrors2(int32_t iRow, float z, float sinPhi, float DzDs, float& ErrY2, float& ErrZ2) const;
   GPUd() void resetCovariance();
 
+  GPUd() float LinearPad2Y(int32_t slice, float pad, float padWidth, int8_t npads) const
+  {
+    const float u = (pad - 0.5f * npads) * padWidth;
+    return (slice >= GPUCA_NSLICES / 2) ? -u : u;
+  }
+
+  GPUd() float LinearY2Pad(int32_t slice, float y, float padWidth, int8_t npads) const
+  {
+    const float u = (slice >= GPUCA_NSLICES / 2) ? -y : y;
+    return u / padWidth + 0.5f * npads;
+  }
+
 #endif
 
  protected:
diff --git a/GPU/GPUTracking/DataCompression/TPCClusterDecompressionCore.inc b/GPU/GPUTracking/DataCompression/TPCClusterDecompressionCore.inc
index 73352182328d5..6ec5b6bfdfe6d 100644
--- a/GPU/GPUTracking/DataCompression/TPCClusterDecompressionCore.inc
+++ b/GPU/GPUTracking/DataCompression/TPCClusterDecompressionCore.inc
@@ -113,7 +113,7 @@ class TPCClusterDecompressionCore
           timeTmp |= 0xFF000000;
         }
         time = timeTmp + ClusterNative::packTime(CAMath::Max(0.f, param.tpcGeometry.LinearZ2Time(slice, track.Z() + zOffset)));
-        float tmpPad = CAMath::Max(0.f, CAMath::Min((float)param.tpcGeometry.NPads(GPUCA_ROW_COUNT - 1), param.tpcGeometry.LinearY2Pad(slice, row, track.Y())));
+        float tmpPad = CAMath::Max(0.f, CAMath::Min((float)param.tpcGeometry.NPads(GPUCA_ROW_COUNT - 1), track.LinearY2Pad(slice, track.Y(), param.tpcGeometry.PadWidth(row), param.tpcGeometry.NPads(row))));
         pad = cmprClusters.padResA[clusterOffset - trackIndex - 1] + ClusterNative::packPad(tmpPad);
         time = time & 0xFFFFFF;
         pad = (uint16_t)pad;
@@ -136,7 +136,7 @@ class TPCClusterDecompressionCore
         pad = cmprClusters.padA[trackIndex];
       }
       const auto cluster = decompressTrackStore(cmprClusters, clusterOffset, slice, row, pad, time, args...);
-      float y = param.tpcGeometry.LinearPad2Y(slice, row, cluster.getPad());
+      float y = track.LinearPad2Y(slice, cluster.getPad(), param.tpcGeometry.PadWidth(row), param.tpcGeometry.NPads(row));
       float z = param.tpcGeometry.LinearTime2Z(slice, cluster.getTime());
       if (clusterIndex == 0) {
         zOffset = z;
@@ -187,4 +187,4 @@ class TPCClusterDecompressionCore
 };
 } // namespace GPUCA_NAMESPACE::gpu
 
-#endif
\ No newline at end of file
+#endif
diff --git a/GPU/GPUTracking/DataTypes/GPUTPCGeometry.h b/GPU/GPUTracking/DataTypes/GPUTPCGeometry.h
index fcafa34547828..e24aa2e236731 100644
--- a/GPU/GPUTracking/DataTypes/GPUTPCGeometry.h
+++ b/GPU/GPUTracking/DataTypes/GPUTPCGeometry.h
@@ -114,7 +114,11 @@ class GPUTPCGeometry // TODO: Make values constexpr
 
   GPUd() float LinearPad2Y(int32_t slice, int32_t row, float pad) const
   {
+#ifdef GPUCA_TPC_GEOMETRY_O2
+    const float u = (pad - 0.5f * (mNPads[row] - 1)) * PadWidth(row);
+#else
     const float u = (pad - 0.5f * mNPads[row]) * PadWidth(row);
+#endif
     return (slice >= GPUCA_NSLICES / 2) ? -u : u;
   }
 
@@ -127,7 +131,11 @@ class GPUTPCGeometry // TODO: Make values constexpr
   GPUd() float LinearY2Pad(int32_t slice, int32_t row, float y) const
   {
     const float u = (slice >= GPUCA_NSLICES / 2) ? -y : y;
+#ifdef GPUCA_TPC_GEOMETRY_O2
+    return u / PadWidth(row) + 0.5f * (mNPads[row] - 1);
+#else
     return u / PadWidth(row) + 0.5f * mNPads[row];
+#endif
   }
 
   GPUd() static float LinearZ2Time(int32_t slice, float z)