ROOT Version 6.36 Release Notes

Introduction

ROOT version 6.36.00 is scheduled for release at the end of May 2025.

For more information, see:

http://root.cern

The following people have contributed to this new version:

Bertrand Bellenot, CERN/EP-SFT,
Jakob Blomer, CERN/EP-SFT,
Philippe Canal, FNAL,
Mattias Ellert, Uppsala University,
Florine de Geus, CERN/University of Twente,
Fernando Hueso Gonzalez, University of Valencia,
Alberto Mecca, University of Turin,
Lorenzo Moneta, CERN/EP-SFT,
Mark Owen, University of Glasgow,
Vincenzo Eduardo Padulano, CERN/EP-SFT,
Giacomo Parolini, CERN/EP-SFT,
Danilo Piparo, CERN/EP-SFT,
Jonas Rembser, CERN/EP-SFT,
Manuel Tobias Schiller, University of Glasgow,
Surya Somayyajula, UMass Amherst,
Petr Stepanov, @petrstepanov,
Dongliang Zhang, University of Science and Technology of China

Deprecation and Removal

• The RooFit legacy interfaces that were deprecated in ROOT 6.34 and scheduled for removal in ROOT 6.36 are removed. See the RooFit section in the 6.34 release notes for a full list.
• The TPython::Eval() function that was deprecated in ROOT 6.34 and scheduled for removal in ROOT 6.36 is removed.
• The RooDataSet constructors to construct a dataset from a part of an existing dataset are deprecated and will be removed in ROOT 6.38. This is to avoid interface duplication. Please use RooAbsData::reduce() instead, or if you need to change the weight column, use the universal constructor with the Import(), Cut(), and WeightVar() arguments.
• The ROOT splash screen was removed for Linux and macOS
• Proof support has been completely removed form RooFit and RooStats, after it was already not working anymore for several releases

Python Interface

RDataFrame

RooFit

Breaking function signature changes

• The RooRealVar::format() function was changed to return a std::string instead of a TString *. The former return type was not memory safe, since the caller had to delete the TString. This pattern was not appropriate for a modern C++ library. If you absolutely need the old return type, wrap the call to format() inside new TString{var.format(..)}. However, this is not recommended.

IO

• New options have been added to TFileMerger (which can be passed as whitespace-separated TStrings via TFileMerger::SetMergeOptions)
  • “FirstSrcCompression”: when merging multiple files, instructs the class-specific merger to use the same compression as the first object of the destination’s class as the destination’s compression. Currently only recognized by the RNTuple merger;
  • “DefaultCompression”: specifies that the merged output should use the class-specific default compression. Currently only meaningful for RNTuple, which has a default compression different from the TFile’s default compression (ZSTD instead of ZLIB). This option is automatically set by hadd when no other compression option is specified;
  • “rntuple.MergingMode=(Filter|Union|Strict)”: RNTuple-specific option that specifies the merging mode that should be used by the RNTupleMerger (see RNTupleMergeOptions);
  • “rntuple.ErrBehavior=(Abort|Skip)”: RNTuple-specific option that specifies the behavior of the RNTupleMerger on error (see link above);
  • “rntuple.ExtraVerbose”: RNTuple-specific option that tells the RNTupleMerger to emit more information during the merge process.
• New attribute for I/O customization rules: CanIgnore. When using this attribute the rule will be ignored if the input is missing from the schema/class-layout they apply to instead of issue a Warning

RDataFrame

Tutorials and Code Examples

Core

Histograms

Math

Graphics

Geometry

Montecarlo

JavaScript ROOT

Class Reference Guide

Build, Configuration and Testing Infrastructure