Skip to content

READMEtreeFastCache.md

Latest commit

 

History

History
126 lines (91 loc) · 3.55 KB

READMEtreeFastCache.md

File metadata and controls

126 lines (91 loc) · 3.55 KB

📦 ROOT Tree Fast Cache System

This repository contains ROOT macros for fast lookup and interpolation of values from TTrees, using:

  • treeFastCache1D.C: 1D cache with nearest-neighbor lookup
  • treeFastCacheND.C: ND cache with exact match in N–1 dimensions and nearest-neighbor in 1 dimension

They are designed for interactive analysis with TTree::Draw, e.g., QA plots, calibration overlays, or smoothed time series.

🔹 treeFastCache1D.C

✅ Features

  • Register 1D lookup maps from TTrees
  • Nearest-neighbor lookup from std::map<double, float>
  • Can register by ID or string name
  • Fast evaluation inside TTree::Draw
  • Alias integration for interactive sessions

🧪 Example

TTree* tree = ...;
int mapID = registerMap1DByName("dcar_vs_time", "time", "dcar_value", tree, "subentry==127");

tree->SetAlias("dcar_smooth", ("getNearest1D(time," + std::to_string(mapID) + ")").c_str());
tree->Draw("dcar_value:dcar_smooth", "indexType==1", "colz", 10000);

🔸 treeFastCacheND.C

✅ Features

  • ND caching with:
    • Exact match in N–1 dimensions
    • Nearest-neighbor lookup in 1 dimension (e.g. time)
  • Uses full double precision for all keys
  • Alias support for TTree::Draw
  • Registration by name with hashed map ID
  • Variadic interface for direct use

🧪 Example: Time Series

TTree* tree = ...;
int mapID = registerMapND("dcar_vs_time", tree, {"subentry"}, "time", "mTSITSTPC.mDCAr_A_NTracks_median", "1");
setNearestNDAlias(tree, "dcar_smooth", "dcar_vs_time", "time", {"subentry"});

tree->Draw("mTSITSTPC.mDCAr_A_NTracks_median:dcar_smooth", "indexType==1", "colz", 10000);

🖊️ Parameters for registerMapND

int registerMapND(
  const std::string& name,       // Unique name of the map
  TTree* tree,                   // Source TTree
  const std::vector<std::string>& exactDims, // Exact-match coordinate names
  const std::string& nearestDim,             // Nearest-match dimension (e.g. time)
  const std::string& valueVar,               // Variable to interpolate
  const std::string& selection               // TTree selection
);

🖊️ Parameters for setNearestNDAlias

void setNearestNDAlias(
  TTree* tree,                          // Target tree
  const std::string& aliasName,        // Alias to create
  const std::string& mapName,          // Name used in registration
  const std::string& nearestCoordExpr, // Nearest-match expression
  const std::vector<std::string>& exactCoordExprs // Exact match expressions
);

⚡️ Alternative: Direct expression

tree->Draw("val:getNearestND(time,mapID,subentry)", ...);

📊 Internal Storage

1D:

std::map<int, std::map<double, float>> registeredMaps;
std::map<std::string, int> nameToMapID;

ND:

std::map<int, std::map<std::vector<double>, std::map<double, double>>> ndCaches;
std::map<std::string, int> ndNameToID;

📌 Best Practices

  • Use aliases to simplify TTree::Draw expressions
  • Use double precision for stability in nearest search
  • Store maps by string name to simplify re-registration
  • Prefer setNearestNDAlias() over manual getNearestND(...) for readability

📤 Future Ideas

  • Optional interpolation (linear, spline)
  • Graceful handling of unmatched keys
  • Caching diagnostics and summary statistics
  • C++ class wrapper for lifecycle + reusability

📜 License

Intended for use in internal physics analyses. No warranty implied.

For more details, see comments and examples inside treeFastCache1D.C and treeFastCacheND.C.