Acts/Vertexing/VertexFitProblem.hpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #include "Acts/Definitions/Algebra.hpp"
0012 #include "Acts/Utilities/Logger.hpp"
0013 #include "Acts/Utilities/Result.hpp"
0014 #include "Acts/Vertexing/TrackAtVertex.hpp"
0015 #include "Acts/Vertexing/Vertex.hpp"
0016 #include "Acts/Vertexing/VertexingError.hpp"
0017
0018 #include <algorithm>
0019 #include <map>
0020 #include <vector>
0021
0022 namespace Acts {
0023
0024 /// @brief Problem-level description of a single vertex candidate
0025 ///
0026 /// This holds everything a caller has to supply about one vertex before it can
0027 /// be fitted: the constraint to fit against, the position the seed finder
0028 /// proposed, and the tracks assigned to it. It deliberately contains no
0029 /// per-iteration scratch data, so it stays meaningful independently of any
0030 /// particular fitter.
0031 struct VertexFitCandidate {
0032   VertexFitCandidate() = default;
0033
0034   /// Construct a candidate from a constraint and a seed position.
0035   /// @param constr Vertex constraint for the fitting procedure
0036   /// @param pos Seed position as proposed by the vertex seed finder
0037   VertexFitCandidate(const Vertex& constr, const Vector4& pos)
0038       : constraint(constr), seedPosition(pos) {}
0039
0040   /// Vertex constraint for the fitting procedure
0041   Vertex constraint;
0042
0043   /// The seed position, i.e. the first estimate of the vertex position as
0044   /// obtained by the vertex seed finder
0045   Vector4 seedPosition{Vector4::Zero()};
0046
0047   /// All tracks that are currently assigned to this vertex
0048   std::vector<InputTrack> trackLinks;
0049 };
0050
0051 /// @brief A multi-vertex fit problem
0052 ///
0053 /// Per-event, caller-owned and fitter-agnostic description of what is to be
0054 /// fitted: a set of vertices, the candidate description of each, and the
0055 /// track-to-vertex association that couples them. Fitter-private scratch data
0056 /// (linearization points, annealing state, field caches) lives in the
0057 /// respective fitter's cache instead, so that this type can be shared between
0058 /// fitters and inspected by callers.
0059 struct VertexFitProblem {
0060   /// The vertices to be fitted
0061   std::vector<Vertex*> vertices;
0062
0063   /// Candidate description (constraint, seed position, tracks) per vertex
0064   std::map<Vertex*, VertexFitCandidate> candidates;
0065
0066   /// Multimap connecting tracks to all of their associated vertices
0067   std::multimap<InputTrack, Vertex*> trackToVertices;
0068
0069   /// Track-at-vertex information for each (track, vertex) pair
0070   std::map<std::pair<InputTrack, Vertex*>, TrackAtVertex> tracksAtVertices;
0071
0072   /// Adds a vertex to @c trackToVertices, using the tracks currently
0073   /// assigned to it in @c candidates
0074   /// @param vtx Vertex to add to the multimap along with its track associations
0075   void addVertexToMultiMap(Vertex& vtx) {
0076     for (auto trk : candidates[&vtx].trackLinks) {
0077       trackToVertices.emplace(trk, &vtx);
0078     }
0079   }
0080
0081   /// Removes a vertex from @c trackToVertices
0082   /// @param vtx Vertex to remove from the multimap along with its track associations
0083   void removeVertexFromMultiMap(const Vertex& vtx) {
0084     std::erase_if(trackToVertices,
0085                   [&vtx](const auto& entry) { return entry.second == &vtx; });
0086   }
0087
0088   /// Remove a vertex from the vertex collection
0089   /// @param vtxToRemove Vertex to remove from the collection
0090   /// @param logger Logger for diagnostic messages
0091   /// @return Result indicating success or failure of the removal operation
0092   Result<void> removeVertexFromCollection(Vertex& vtxToRemove,
0093                                           const Logger& logger) {
0094     auto it = std::ranges::find(vertices, &vtxToRemove);
0095     // Check if the value was found before erasing
0096     if (it == vertices.end()) {
0097       ACTS_ERROR("vtxToRemove is not part of the vertex collection.");
0098       return VertexingError::ElementNotFound;
0099     }
0100     // Erase the element if found
0101     vertices.erase(it);
0102     return {};
0103   }
0104 };
0105
0106 }  // namespace Acts