MCTrack: Calculate energy in double

sawenzel · noferini · commit 319f4e499c7c · 2024-04-26T14:39:14.000+02:00
in previous version, intermediate steps happened in float with a precision loss on the global result. Fixes another instance of the problem discussed here: https://its.cern.ch/jira/browse/ALIROOT-8233
diff --git a/DataFormats/simulation/include/SimulationDataFormat/MCTrack.h b/DataFormats/simulation/include/SimulationDataFormat/MCTrack.h
@@ -298,8 +298,10 @@ template <typename T>
 inline Double_t MCTrackT<T>::GetEnergy() const
 {
   const auto mass = GetMass();
-  return std::sqrt(mass * mass + mStartVertexMomentumX * mStartVertexMomentumX +
-                   mStartVertexMomentumY * mStartVertexMomentumY + mStartVertexMomentumZ * mStartVertexMomentumZ);
+  Double_t px = mStartVertexMomentumX;
+  Double_t py = mStartVertexMomentumY;
+  Double_t pz = mStartVertexMomentumZ;
+  return std::sqrt(mass * mass + px * px + py * py + pz * pz);
 }
 
 template <typename T>

Original file line number	Diff line number	Diff line change
`@@ -298,8 +298,10 @@ template <typename T>`
`298`	`298`	`inline Double_t MCTrackT<T>::GetEnergy() const`
`299`	`299`	`{`
`300`	`300`	`const auto mass = GetMass();`
`301`		`- return std::sqrt(mass * mass + mStartVertexMomentumX * mStartVertexMomentumX +`
`302`		`- mStartVertexMomentumY * mStartVertexMomentumY + mStartVertexMomentumZ * mStartVertexMomentumZ);`
	`301`	`+ Double_t px = mStartVertexMomentumX;`
	`302`	`+ Double_t py = mStartVertexMomentumY;`
	`303`	`+ Double_t pz = mStartVertexMomentumZ;`
	`304`	`+ return std::sqrt(mass * mass + px * px + py * py + pz * pz);`
`303`	`305`	`}`
`304`	`306`
`305`	`307`	`template <typename T>`