AliceO2Group · spulawsk · Aug 6, 2026 · Aug 7, 2026 · Aug 7, 2026
@@ -19,6 +19,7 @@ o2_add_library(DataFormatsFT0
           src/CTF.cxx
           src/LookUpTable.cxx
           src/SlewingCoef.cxx
+	  src/PMLookupTable.cxx
 
   PUBLIC_LINK_LIBRARIES O2::FT0Base
                         O2::DataFormatsFIT

@@ -0,0 +1,58 @@
+// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+#ifndef O2_FT0_PMLOOKUPTABLE_H_
+#define O2_FT0_PMLOOKUPTABLE_H_
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <map>
+
+#include "FT0Base/Constants.h"
+
+namespace o2::ft0
+{
+
+/// Cached mapping between FT0 channels and PM modules.
+///
+/// The mapping is constructed once from SingleLUT and can then be reused by
+/// digitization, reconstruction, trigger and QA code without reparsing the LUT.
+class PMLookupTable
+{
+ public:
+  using ChannelID = uint16_t;
+  using PMHash = uint8_t;
+  using PMMap = std::map<PMHash, bool>; // PM hash -> true for A side, false for C side
+
+  /// Return the process-wide immutable lookup table.
+  static const PMLookupTable& Instance();
+
+  /// Return the PM hash assigned to a detector channel.
+  PMHash getPMHash(ChannelID channelID) const;
+
+  /// Return true for an A-side PM and false for a C-side PM.
+  bool isASide(PMHash pmHash) const;
+
+  /// Return all PM hashes and their sides. TCM entries are not included.
+  const PMMap& getPMs() const noexcept { return mPMHash2IsASide; }
+
+ private:
+  PMLookupTable();
+
+  std::array<PMHash, Constants::sNCHANNELS_PM> mChannelID2PMHash{};
+  std::array<bool, Constants::sNCHANNELS_PM> mChannelIsMapped{};
+  PMMap mPMHash2IsASide;
+};
+
+} // namespace o2::ft0
+
+#endif // O2_FT0_PMLOOKUPTABLE_H_
@@ -0,0 +1,109 @@
+// Copyright 2019-2020 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+#include "DataFormatsFT0/PMLookupTable.h"
+
+#include "DataFormatsFT0/LookUpTable.h"
+#include "Framework/Logger.h"
+
+#include <algorithm>
+#include <charconv>
+#include <map>
+#include <limits>
+#include <string>
+#include <system_error>
+
+namespace o2::ft0
+{
+
+const PMLookupTable& PMLookupTable::Instance()
+{
+  static const PMLookupTable table;
+  return table;
+}
+
+PMLookupTable::PMLookupTable()
+{
+  std::map<std::string, PMHash> moduleName2Hash;
+
+  auto lut = SingleLUT::Instance().getVecMetadataFEE();
+  std::sort(lut.begin(), lut.end(), [](const auto& lhs, const auto& rhs) {
+    return lhs.mModuleName < rhs.mModuleName;
+  });
+
+  unsigned int nextHash = 0;
+
+  for (const auto& entry : lut) {
+    const auto& moduleName = entry.mModuleName;
+    const auto& moduleType = entry.mModuleType;
+    const auto& channelString = entry.mChannelID;
+
+    if (nextHash > static_cast<unsigned int>(std::numeric_limits<PMHash>::max())) {
+      LOG(fatal) << "Too many FT0 FEE modules to represent with PMHash";
+    }
+
+    auto [moduleIt, inserted] = moduleName2Hash.emplace(moduleName, static_cast<PMHash>(nextHash));
+
+    if (inserted) {
+      const auto moduleHash = moduleIt->second;
+      if (moduleName.find("PMA") != std::string::npos) {
+        mPMHash2IsASide.emplace(moduleHash, true);
+      } else if (moduleName.find("PMC") != std::string::npos) {
+        mPMHash2IsASide.emplace(moduleHash, false);
+      } else if (moduleType != "TCM") {
+        LOG(fatal) << "Unknown FT0 module in LUT: " << moduleName
+                   << " (type " << moduleType << ")";
+      }
+      ++nextHash;
+    }
+
+    int channelID = -1;
+    const char* begin = channelString.data();
+    const char* end = begin + channelString.size();
+    const auto [ptr, error] = std::from_chars(begin, end, channelID);
+    const bool isNumericChannel = error == std::errc{} && ptr == end;
+
+    if (isNumericChannel) {
+      if (channelID < 0 || channelID >= Constants::sNCHANNELS_PM) {
+        LOG(fatal) << "Incorrect FT0 LUT entry: channel " << channelString
+                   << " | module " << moduleName;
+      }
+
+      mChannelID2PMHash[channelID] = moduleIt->second;
+      mChannelIsMapped[channelID] = true;
+    } else if (moduleType != "TCM") {
+      LOG(fatal) << "Non-TCM FT0 module without numerical channel ID: channel "
+                 << channelString << " | module " << moduleName;
+    }
+  }
+}
+
+PMLookupTable::PMHash PMLookupTable::getPMHash(ChannelID channelID) const
+{
+  if (channelID >= Constants::sNCHANNELS_PM) {
+    LOG(fatal) << "FT0 channel ID outside valid range: " << channelID;
+  }
+  if (!mChannelIsMapped[channelID]) {
+    LOG(fatal) << "FT0 channel is not mapped to a PM: " << channelID;
+  }
+  return mChannelID2PMHash[channelID];
+}
+
+bool PMLookupTable::isASide(PMHash pmHash) const
+{
+  const auto it = mPMHash2IsASide.find(pmHash);
+  if (it == mPMHash2IsASide.end()) {
+    LOG(fatal) << "Unknown FT0 PM hash: " << static_cast<unsigned int>(pmHash);
+  }
+  return it->second;
+}
+
+} // namespace o2::ft0