AliceO2Group · f3sch · Aug 12, 2026
@@ -13,6 +13,7 @@ o2_add_library(ITStracking
                TARGETVARNAME targetName
                SOURCES src/ClusterLines.cxx
                        src/Cluster.cxx
+                       src/CapacityEstimator.cxx
                        src/Configuration.cxx
                        src/FastMultEstConfig.cxx
                        src/FastMultEst.cxx

@@ -0,0 +1,110 @@
+// Copyright 2019-2026 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.
+///
+/// \file CapacityEstimator.h
+/// \brief Cross-timeframe output-size prediction.
+///
+
+#ifndef TRACKINGITSU_INCLUDE_CAPACITYESTIMATOR_H_
+#define TRACKINGITSU_INCLUDE_CAPACITYESTIMATOR_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+
+namespace o2::its
+{
+
+enum SlabSite : uint8_t {
+  Tracklets = 0,
+  Cells,
+  Neighbours,
+  Roads,
+  NSlabSite,
+};
+constexpr const char* const SlabSiteNames[SlabSite::NSlabSite]{"Tracklets", "Cells", "Neighbours", "Roads"};
+
+class CapacityEstimator
+{
+ public:
+  struct Config {
+    float alpha{0.2f};
+    float marginInit{1.30f};
+    float marginMin{1.10f};
+    float marginMax{4.00f};
+    float marginUp{1.50f};
+    float marginOverflowSlack{1.05f};
+    float marginDown{0.98f};
+    float lowWatermark{0.60f};
+    uint32_t decayAfter{2};
+    size_t floorSlots{1024};
+  };
+
+  using KeyType = uint64_t;
+
+  struct Decoded {
+    SlabSite site;
+    int iteration;
+    int variant;
+    int slot;
+  };
+
+  static constexpr KeyType makeKey(SlabSite site, int iteration, int variant, int slot) noexcept
+  {
+    return (static_cast<KeyType>(site) << 56) |
+           (static_cast<KeyType>(iteration & 0xFF) << 48) |
+           (static_cast<KeyType>(variant & 0xFFFF) << 32) |
+           static_cast<KeyType>(static_cast<uint32_t>(slot));
+  }
+
+  static constexpr Decoded decodeKey(KeyType key) noexcept
+  {
+    return {
+      .site = static_cast<SlabSite>((key >> 56) & 0xFF),
+      .iteration = static_cast<int>((key >> 48) & 0xFF),
+      .variant = static_cast<int>((key >> 32) & 0xFFFF),
+      .slot = static_cast<int>(static_cast<uint32_t>(key & 0xFFFFFFFF))};
+  }
+
+  static constexpr int makeVariant(int high, int low) noexcept
+  {
+    return ((high & 0xFF) << 8) | (low & 0xFF);
+  }
+
+  static constexpr int getVariantHigh(int variant) noexcept
+  {
+    return (variant >> 8) & 0xFF;
+  }
+
+  static constexpr int getVariantLow(int variant) noexcept
+  {
+    return variant & 0xFF;
+  }
+
+  CapacityEstimator();
+  explicit CapacityEstimator(Config cfg);
+  ~CapacityEstimator();
+  CapacityEstimator(const CapacityEstimator&) = delete;
+  CapacityEstimator& operator=(const CapacityEstimator&) = delete;
+
+  void reset();
+  size_t capacity(uint64_t key, double scale) const;
+  void update(uint64_t key, double scale, size_t emitted, size_t capacityUsed, bool overflowed, bool memoryLimited);
+  void print() const;
+
+ private:
+  struct Impl;
+  std::unique_ptr<Impl> mImpl;
+};
+
+} // namespace o2::its
+
+#endif /* TRACKINGITSU_INCLUDE_CAPACITYESTIMATOR_H_ */