feat: minimum number of compatible top SPs to trigger filterSeeds_2Sp…

…Fixed (#1930)

This is intended to reduce the number of filter iterations by setting a minimum number of compatible top SP candidates that are necessary to run the seed confirmation.
It should not affect the physics performance

Core/include/Acts/Seeding/SeedFilter.hpp

@@ -26,6 +26,10 @@ struct SeedFilterState {
   float zOrigin = 0;
   // number of minimum top SPs in seed confirmation
   size_t nTopSeedConf = 0;
+  // radius of bottom component of seed that is used to define the number of
+  // compatible top required
+  float rMaxSeedConf =
+      std::numeric_limits<float>::max();  // Acts::UnitConstants::mm
   // number of high quality seeds in seed confirmation
   std::size_t numQualitySeeds = 0;
   // number of seeds that did not pass the quality confirmation but were still

Core/include/Acts/Seeding/SeedFinder.ipp

@@ -143,6 +143,9 @@ void SeedFinder<external_spacepoint_t, platform_t>::createSeedsForGroup(
       seedFilterState.nTopSeedConf = rM > seedConfRange.rMaxSeedConf
                                          ? seedConfRange.nTopForLargeR
                                          : seedConfRange.nTopForSmallR;
+      // set max bottom radius for seed confirmation
+      seedFilterState.rMaxSeedConf = seedConfRange.rMaxSeedConf;
+      // continue if number of top SPs is smaller than minimum
       if (state.compatTopSP.size() < seedFilterState.nTopSeedConf) {
         continue;
       }
@@ -368,6 +371,18 @@ void SeedFinder<external_spacepoint_t, platform_t>::filterCandidates(
       rotationTermsUVtoXY[1] = spM.y() * sinTheta / spM.radius();
     }
 
+    // minimum number of compatible top SPs to trigger the filter for a certain
+    // middle bottom pair if seedConfirmation is false we always ask for at
+    // least one compatible top to trigger the filter
+    size_t minCompatibleTopSPs = 2;
+    if (!m_config.seedConfirmation or
+        state.compatBottomSP[b]->radius() > seedFilterState.rMaxSeedConf) {
+      minCompatibleTopSPs = 1;
+    }
+    if (m_config.seedConfirmation and seedFilterState.numQualitySeeds) {
+      minCompatibleTopSPs++;
+    }
+
     for (size_t index_t = t0; index_t < numTopSP; index_t++) {
       const std::size_t& t = sorted_tops[index_t];
 
@@ -587,7 +602,8 @@ void SeedFinder<external_spacepoint_t, platform_t>::filterCandidates(
       state.ptVec.push_back(pT);
     }  // loop on tops
 
-    if (state.topSpVec.empty()) {
+    // continue if number of top SPs is smaller than minimum required for filter
+    if (state.topSpVec.size() < minCompatibleTopSPs) {
       continue;
     }
 

Core/include/Acts/Seeding/SeedFinderOrthogonal.ipp

@@ -260,6 +260,9 @@ void SeedFinderOrthogonal<external_spacepoint_t>::filterCandidates(
     seedFilterState.nTopSeedConf = rM > seedConfRange.rMaxSeedConf
                                        ? seedConfRange.nTopForLargeR
                                        : seedConfRange.nTopForSmallR;
+    // set max bottom radius for seed confirmation
+    seedFilterState.rMaxSeedConf = seedConfRange.rMaxSeedConf;
+    // continue if number of top SPs is smaller than minimum
     if (top.size() < seedFilterState.nTopSeedConf) {
       return;
     }
@@ -331,6 +334,18 @@ void SeedFinderOrthogonal<external_spacepoint_t>::filterCandidates(
     // multiply the squared sigma onto the squared scattering
     scatteringInRegion2 *= m_config.sigmaScattering * m_config.sigmaScattering;
 
+    // minimum number of compatible top SPs to trigger the filter for a certain
+    // middle bottom pair if seedConfirmation is false we always ask for at
+    // least one compatible top to trigger the filter
+    size_t minCompatibleTopSPs = 2;
+    if (!m_config.seedConfirmation or
+        bottom[b]->radius() > seedFilterState.rMaxSeedConf) {
+      minCompatibleTopSPs = 1;
+    }
+    if (m_config.seedConfirmation and seedFilterState.numQualitySeeds) {
+      minCompatibleTopSPs++;
+    }
+
     // clear all vectors used in each inner for loop
     top_valid.clear();
     curvatures.clear();
@@ -431,11 +446,14 @@ void SeedFinderOrthogonal<external_spacepoint_t>::filterCandidates(
       }
     }
 
-    if (!top_valid.empty()) {
-      m_config.seedFilter->filterSeeds_2SpFixed(
-          *bottom[b], middle, top_valid, curvatures, impactParameters,
-          seedFilterState, candidates_collector);
+    // continue if number of top SPs is smaller than minimum required for filter
+    if (top.size() < minCompatibleTopSPs) {
+      continue;
     }
+    m_config.seedFilter->filterSeeds_2SpFixed(
+        *bottom[b], middle, top_valid, curvatures, impactParameters,
+        seedFilterState, candidates_collector);
+
   }  // loop on bottoms
 }