ROOT

For other uses of "root", see root (disambiguation).

ROOT

Example ROOT plot showing regions of interest in a 2D distribution
Developer(s)	CERN
Stable release	5.32/02 / March 27, 2012
Written in	C++
Operating system	Cross-platform
Type	Data analysis
License	LGPL/GPL
Website	http://root.cern.ch/

ROOT is an object-oriented program and library developed by CERN. It was originally designed for particle physics data analysis and contains several features specific to this field, but it is also used in other applications such as astronomy and data mining.

Description

CERN maintained a program library written in FORTRAN for many years; development and maintenance were discontinued in 2003 in favour of ROOT, written in C++. ROOT development was initiated by René Brun and Fons Rademakers in 1994. Some parts are published under the LGPL, and others are based on GPL software and thus are also published under the terms of the GPL. It provides platform independent access to a computer's graphics subsystem and operating system using abstract layers. Parts of the abstract platform are: a graphical user interface and a GUI builder, container classes, reflection, a C++ script and command line interpreter (CINT), object serialization and persistence.

The packages provided by ROOT include those for

• histogramming and graphing to view and analyze distributions and functions,
• curve fitting (regression analysis) and minimization of functionals,
• statistics tools used for data analysis,
• matrix algebra,
• four-vector computations, as used in high energy physics,
• standard mathematical functions,
• multivariate data analysis, e.g. using neural networks,
• image manipulation, used, for instance, to analyze astronomical pictures,
• access to distributed data (in the context of the Grid),
• distributed computing, to parallelize data analyses,
• persistence and serialization of objects, which can cope with changes in class definitions of persistent data,
• access to databases,
• 3D visualizations (geometry)
• creating files in various graphics formats, like PostScript, PNG, SVG,
• interfacing Python and Ruby code in both directions,
• interfacing Monte Carlo event generators.

A key feature of ROOT is a data container called tree, with its substructures branches and leaves. A tree can be seen as a sliding window to the raw data, as stored in a file. Data from the next entry in the file can be retrieved by advancing the index in the tree. This avoids memory allocation problems associated with object creation, and allows the tree to act as a lightweight container while handling buffering invisibly.

ROOT is designed for high computing efficiency, as it is required to process data from the Large Hadron Collider's experiments estimated at several petabytes per year. As of 2009 ROOT is mainly used in data analysis and data acquisition in high energy physics experiments, and most current experimental plots and results in those subfields are obtained using ROOT.

The inclusion of the CINT C++ interpreter makes this package very versatile as it can be used in interactive, scripted and compiled modes in a manner similar to commercial products like MATLAB.

Criticisms

Criticisms of ROOT include its difficulty for beginners, as well as various aspects of its design and implementation. Frequent causes of frustration include extreme code bloat, heavy use of global variables, and a perverse class hierarchy. From time to time these issues are discussed on the ROOT users mailing list. While scientists dissatisfied with ROOT have in the past manage to work around its flaws, some of the shortcomings are slowly being addressed by the ROOT team. The CINT interpreter, for example, is in the process of being replaced, and numerous small bugs are fixed with every release.

Applications of ROOT

Several particle physics experiments have written software based on ROOT, often in favor of using more generic solutions (e.g. using ROOT containers instead of STL).

• Some of the running particle physics experiments using software based on ROOT
  • ALICE
  • ATLAS
  • BaBar
  • Belle Experiment
  • CB-ELSA/TAPS
  • CDF
  • CMS
  • COMPASS
  • DZero
  • GRAPES-3
  • H1
  • LHCb
  • MINERνA
  • MINOS
  • NEXT
  • PEN
  • PHENIX
  • PHOBOS
  • STAR
  • T2K
  • ZEUS
  • CRESST
  • OPERA

• Future particle physics experiments currently developing software based on ROOT
  • NOνA
  • CBM
  • PANDA
  • BELLE II
  • Long Baseline Neutrino Experiment (LBNE)

• Astroparticle physics projects using ROOT
  • AMS
  • ANTARES
  • DMTPC
  • Fermi
  • ICECUBE
  • H.E.S.S.
  • MAGIC
  • Milagro (experiment)
  • Pierre Auger Observatory
  • VERITAS
  • PAMELA
  • PoGOLite

See also

• Matplotlib - a plotting and analysis system for Python
• SciPy - a scientific data analysis system for Python, based on the NumPy classes
• Perl Data Language - a set of array programming extensions to the Perl programming language
• HippoDraw — an alternative C++-based data analysis system
• Java Analysis Studio — a Java-based AIDA-compliant data analysis system
• SCaViS — a Java-based data analysis framework based on FreeHEP libraries
• R programming language
• AIDA (computing) — open interfaces and formats for particle physics data processing
• GEANT
• PAW
• IGOR Pro
• Scientific Linux
• Scientific computing
• OpenDX
• OpenScientist
• CERN Program Library — legacy program library written in Fortran77, still available but not updated

External links

• The ROOT System Home Page
• ROOT users mailing list
• The Qt/ROOT System Home Page
• GSI Object Oriented On-line Off-line system, an alternative GUI for ROOT based on QT/ROOT..
• The RooFit Toolkit for Data Modeling, an extension to ROOT to facilitate maximum likelihood fits
• Dynamic Perl Binding akin to PyROOT