SpacePointFormation/detail/SpacePointBuilder.ipp

0001 // This file is part of the Acts project.
0002 //
0003 // Copyright (C) 2018-2022 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 http://mozilla.org/MPL/2.0/.
0008
0009 #include "Acts/Definitions/Algebra.hpp"
0010
0011 namespace Acts {
0012
0013 template <typename spacepoint_t>
0014 SpacePointBuilder<spacepoint_t>::SpacePointBuilder(
0015     const SpacePointBuilderConfig& cfg, BuilderFunction func,
0016     std::unique_ptr<const Logger> logger)
0017     : m_config(cfg), m_spConstructor(func), m_logger(std::move(logger)) {
0018   m_spUtility = std::make_shared<SpacePointUtility>(cfg);
0019 }
0020
0021 template <typename spacepoint_t>
0022 template <template <typename...> typename container_t>
0023 void SpacePointBuilder<spacepoint_t>::buildSpacePoint(
0024     const GeometryContext& gctx, const std::vector<SourceLink>& sourceLinks,
0025     const SpacePointBuilderOptions& opt,
0026     std::back_insert_iterator<container_t<spacepoint_t>> spacePointIt) const {
0027   const unsigned int num_slinks = sourceLinks.size();
0028
0029   Acts::Vector3 gPos = Acts::Vector3::Zero();
0030   std::optional<Acts::ActsScalar> gTime = std::nullopt;
0031   Acts::Vector2 gCov = Acts::Vector2::Zero();
0032   std::optional<Acts::ActsScalar> gCovT = std::nullopt;
0033
0034   if (num_slinks == 1) {  // pixel SP formation
0035     auto slink = sourceLinks.at(0);
0036     auto [param, cov] = opt.paramCovAccessor(slink);
0037     std::tie(gPos, gTime, gCov, gCovT) = m_spUtility->globalCoords(
0038         gctx, slink, m_config.slSurfaceAccessor, param, cov);
0039   } else if (num_slinks == 2) {  // strip SP formation
0040
0041     const auto& ends1 = opt.stripEndsPair.first;
0042     const auto& ends2 = opt.stripEndsPair.second;
0043
0044     Acts::SpacePointParameters spParams;
0045
0046     if (!m_config.usePerpProj) {  // default strip SP building
0047
0048       auto spFound = m_spUtility->calculateStripSPPosition(
0049           ends1, ends2, opt.vertex, spParams, opt.stripLengthTolerance);
0050
0051       if (!spFound.ok()) {
0052         spFound = m_spUtility->recoverSpacePoint(spParams,
0053                                                  opt.stripLengthGapTolerance);
0054       }
0055
0056       if (!spFound.ok()) {
0057         return;
0058       }
0059
0060       gPos = 0.5 *
0061              (ends1.first + ends1.second + spParams.m * spParams.firstBtmToTop);
0062
0063     } else {  // for cosmic without vertex constraint
0064
0065       auto resultPerpProj =
0066           m_spUtility->calcPerpendicularProjection(ends1, ends2, spParams);
0067
0068       if (!resultPerpProj.ok()) {
0069         return;
0070       }
0071       gPos = ends1.first + resultPerpProj.value() * spParams.firstBtmToTop;
0072     }
0073
0074     double theta = std::acos(
0075         spParams.firstBtmToTop.dot(spParams.secondBtmToTop) /
0076         (spParams.firstBtmToTop.norm() * spParams.secondBtmToTop.norm()));
0077
0078     gCov = m_spUtility->calcRhoZVars(gctx, sourceLinks.at(0), sourceLinks.at(1),
0079                                      m_config.slSurfaceAccessor,
0080                                      opt.paramCovAccessor, gPos, theta);
0081
0082   } else {
0083     ACTS_ERROR("More than 2 sourceLinks are given for a space point.");
0084   }
0085   boost::container::static_vector<SourceLink, 2> slinks(sourceLinks.begin(),
0086                                                         sourceLinks.end());
0087
0088   spacePointIt = m_spConstructor(gPos, gTime, gCov, gCovT, std::move(slinks));
0089 }
0090
0091 template <typename spacepoint_t>
0092 void SpacePointBuilder<spacepoint_t>::makeSourceLinkPairs(
0093     const GeometryContext& gctx, const std::vector<SourceLink>& slinksFront,
0094     const std::vector<SourceLink>& slinksBack,
0095     std::vector<std::pair<SourceLink, SourceLink>>& slinkPairs,
0096     const StripPairOptions& pairOpt) const {
0097   if (slinksFront.empty() || slinksBack.empty()) {
0098     return;
0099   }
0100   double minDistance = 0;
0101   unsigned int closestIndex = 0;
0102
0103   for (unsigned int i = 0; i < slinksFront.size(); i++) {
0104     const auto& slinkFront = slinksFront[i];
0105     minDistance = std::numeric_limits<double>::max();
0106     closestIndex = slinksBack.size();
0107     for (unsigned int j = 0; j < slinksBack.size(); j++) {
0108       const auto& slinkBack = slinksBack[j];
0109
0110       const auto [paramFront, covFront] = pairOpt.paramCovAccessor(slinkFront);
0111       const auto [gposFront, gtimeFront, gcovFront, gcovtFront] =
0112           m_spUtility->globalCoords(gctx, slinkFront,
0113                                     m_config.slSurfaceAccessor, paramFront,
0114                                     covFront);
0115
0116       const auto [paramBack, covBack] = pairOpt.paramCovAccessor(slinkBack);
0117       const auto [gposBack, gtimeBack, gcovBack, gcovtBack] =
0118           m_spUtility->globalCoords(gctx, slinkBack, m_config.slSurfaceAccessor,
0119                                     paramBack, covBack);
0120
0121       auto res = m_spUtility->differenceOfMeasurementsChecked(
0122           gposFront, gposBack, pairOpt.vertex, pairOpt.diffDist,
0123           pairOpt.diffPhi2, pairOpt.diffTheta2);
0124       if (!res.ok()) {
0125         continue;
0126       }
0127       const auto distance = res.value();
0128       if (distance >= 0. && distance < minDistance) {
0129         minDistance = distance;
0130         closestIndex = j;
0131       }
0132     }
0133     if (closestIndex < slinksBack.size()) {
0134       slinkPairs.emplace_back(slinksFront[i], slinksBack[closestIndex]);
0135     }
0136   }
0137 }
0138
0139 }  // namespace Acts