From c7cbb7168ef12770eda98c6aba729252c93aff21 Mon Sep 17 00:00:00 2001
From: Sandro Wenzel <sandro.wenzel@cern.ch>
Date: Fri, 6 Mar 2026 07:37:01 +0100
Subject: [PATCH 1/2] Improve safety calculations in Tessellated solid

Optimization: Cache safety and only recalculate when becoming invalid.
This works since safety can be underestimated and does not need to be
precise. Precise safety evaluation for Tessellated is expensive.
---
 .../include/DetectorsBase/O2Tessellated.h     |  8 +++++++
 Detectors/Base/src/O2Tessellated.cxx          | 24 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/Detectors/Base/include/DetectorsBase/O2Tessellated.h b/Detectors/Base/include/DetectorsBase/O2Tessellated.h
index 0a1cee8b3e01f..7a1a3945c80d8 100644
--- a/Detectors/Base/include/DetectorsBase/O2Tessellated.h
+++ b/Detectors/Base/include/DetectorsBase/O2Tessellated.h
@@ -133,6 +133,14 @@ class O2Tessellated : public TGeoBBox
   template <bool closest_facet = false>
   Double_t SafetyKernel(const Double_t* point, bool in, int* closest_facet_id = nullptr) const;
 
+  // cached values for safety
+  mutable float mLast_x;
+  mutable float mLast_y;
+  mutable float mLast_z;
+  mutable float mCachedSafety;
+  mutable size_t cached_counter = 0;
+  mutable size_t call_counter = 0;
+
   ClassDefOverride(O2Tessellated, 1) // tessellated shape class
 };
 
diff --git a/Detectors/Base/src/O2Tessellated.cxx b/Detectors/Base/src/O2Tessellated.cxx
index 256a70e5a697a..80d5935eff615 100644
--- a/Detectors/Base/src/O2Tessellated.cxx
+++ b/Detectors/Base/src/O2Tessellated.cxx
@@ -1349,8 +1349,30 @@ Double_t O2Tessellated::Safety(const Double_t* point, Bool_t in) const
   // we could use some caching here (in future) since queries to the solid will likely
   // be made with some locality
 
+  if (in) {
+    call_counter++;
+    // distance to last known evaluation
+    const auto xd = float(point[0]) - mLast_x;
+    const auto yd = float(point[1]) - mLast_y;
+    const auto zd = float(point[2]) - mLast_z;
+    const auto d2 = xd * xd + yd * yd + zd * zd;
+
+    if (d2 < mCachedSafety * mCachedSafety) {
+      // we moved less than known safety
+      mCachedSafety - std::sqrt(d2);
+      cached_counter++;
+    }
+  }
+
   // fall-back to precise safety kernel
-  return SafetyKernel<false>(point, in);
+  const auto safety = SafetyKernel<false>(point, in);
+  if (in) {
+    mLast_x = point[0];
+    mLast_y = point[1];
+    mLast_z = point[2];
+    mCachedSafety = safety;
+  }
+  return safety;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

From 5afccc84cfd693fd53df0b1d679d06d649085310 Mon Sep 17 00:00:00 2001
From: Sandro Wenzel <sandro.wenzel@cern.ch>
Date: Fri, 6 Mar 2026 16:56:23 +0100
Subject: [PATCH 2/2] Fix cached safety calculation in O2Tessellated

---
 Detectors/Base/src/O2Tessellated.cxx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Detectors/Base/src/O2Tessellated.cxx b/Detectors/Base/src/O2Tessellated.cxx
index 80d5935eff615..5c52625841868 100644
--- a/Detectors/Base/src/O2Tessellated.cxx
+++ b/Detectors/Base/src/O2Tessellated.cxx
@@ -1359,8 +1359,8 @@ Double_t O2Tessellated::Safety(const Double_t* point, Bool_t in) const
 
     if (d2 < mCachedSafety * mCachedSafety) {
       // we moved less than known safety
-      mCachedSafety - std::sqrt(d2);
       cached_counter++;
+      return mCachedSafety - std::sqrt(d2);
     }
   }
 
@@ -1528,4 +1528,4 @@ void O2Tessellated::CalculateNormals()
   }
 }
 
-// NOLINTEND
\ No newline at end of file
+// NOLINTEND