Define/use unbiased GPUTPCGeometry LinearY2PadC and LinearPad2YC

Author: shahor02

GPU/GPUTracking/DataTypes/GPUTPCGeometry.h

@@ -127,6 +127,12 @@ class GPUTPCGeometry // TODO: Make values constexpr
     return (slice >= GPUCA_NSLICES / 2) ? -u : u;
   }
 
+  GPUd() float LinearPad2YC(int32_t slice, int32_t row, float pad) const
+  {
+    const float u = (pad - 0.5f * (mNPads[row] - 1)) * PadWidth(row);
+    return (slice >= GPUCA_NSLICES / 2) ? -u : u;
+  }
+
   GPUd() static float LinearTime2Z(int32_t slice, float time)
   {
     const float v = 250.f - time * FACTOR_T2Z; // Used in compression, must remain constant at 250cm!
@@ -139,6 +145,12 @@ class GPUTPCGeometry // TODO: Make values constexpr
     return u / PadWidth(row) + 0.5f * mNPads[row];
   }
 
+  GPUd() float LinearY2PadC(int32_t slice, int32_t row, float y) const
+  {
+    const float u = (slice >= GPUCA_NSLICES / 2) ? -y : y;
+    return u / PadWidth(row) + 0.5f * (mNPads[row] - 1);  // unbiased version of LinearY2Pad
+  }
+
   GPUd() static float LinearZ2Time(int32_t slice, float z)
   {
     const float v = (slice >= GPUCA_NSLICES / 2) ? -z : z;

GPU/GPUTracking/Merger/GPUTPCGMTrackParam.cxx

@@ -669,7 +669,7 @@ GPUd() bool GPUTPCGMTrackParam::AttachClustersPropagate(const GPUTPCGMMerger* GP
     if (dodEdx && iRow + step == toRow) {
       float yUncorrected, zUncorrected;
       Merger->GetConstantMem()->calibObjects.fastTransformHelper->InverseTransformYZtoNominalYZ(slice, iRow, mP[0], mP[1], yUncorrected, zUncorrected);
-      uint32_t pad = CAMath::Float2UIntRn(Merger->Param().tpcGeometry.LinearY2Pad(slice, iRow, yUncorrected));
+      uint32_t pad = CAMath::Float2UIntRn(Merger->Param().tpcGeometry.LinearY2PadC(slice, iRow, yUncorrected));
       if (pad >= Merger->Param().tpcGeometry.NPads(iRow) || (Merger->GetConstantMem()->calibObjects.dEdxCalibContainer && Merger->GetConstantMem()->calibObjects.dEdxCalibContainer->isDead(slice, iRow, pad))) {
         dodEdx = false;
       }

GPU/GPUTracking/SliceTracker/GPUTPCTrackletConstructor.cxx

@@ -393,7 +393,7 @@ GPUdic(2, 1) void GPUTPCTrackletConstructor::UpdateTracklet(int32_t /*nBlocks*/,
       (void)found;
 #if defined(GPUCA_HAVE_O2HEADERS) && !defined(__OPENCL1__)
       if (!found && tracker.GetConstantMem()->calibObjects.dEdxCalibContainer) {
-        uint32_t pad = CAMath::Float2UIntRn(tracker.Param().tpcGeometry.LinearY2Pad(tracker.ISlice(), iRow, yUncorrected));
+        uint32_t pad = CAMath::Float2UIntRn(tracker.Param().tpcGeometry.LinearY2PadC(tracker.ISlice(), iRow, yUncorrected));
         if (pad < tracker.Param().tpcGeometry.NPads(iRow) && tracker.GetConstantMem()->calibObjects.dEdxCalibContainer->isDead(tracker.ISlice(), iRow, pad)) {
           r.mNMissed--;
           rowHit = CALINK_DEAD_CHANNEL;