Introduction to ROOT1 Summer Students Lecture 20 July 2005 [email protected] Introduction to ROOT

Introduction to ROOT 1

Summer Students Lecture20 July 2005

[email protected]

ftp://root.cern.ch/root/SummerStudents2005.ppt

Introduction to ROOT


ROOT in a Nutshell The ROOT system is an Object Oriented framework for

large scale data handling applications Written in C++ Provides, among others,

an efficient data storage and access system designed to support structured data sets (PetaBytes)

a query system to extract data from these data sets a C++ interpreter advanced statistical analysis algorithms (multi dimensional

histogramming, fitting, minimization and cluster finding) scientific visualization tools with 2D and 3D graphics an advanced Graphical User Interface

The user interacts with ROOT via a graphical user interface, the command line or batch scripts

The command and scripting language is C++, thanks to the embedded CINT C++ interpreter and large scripts can be compiled and dynamically loaded


ROOT: An Open Source Project

The project is developed as a collaboration between:

Full time developers: 12 people full time at CERN 2 developers at FermiLab 1 developer in Japan (Agilent Technologies) 2 developers at MIT

Large number of part-time contributors Source freely available (cvs and tarballs) Release early, release often Several thousand users giving feedback

and providing many small contributions


27 binarytar balls+ source

Download Source and Binaries


Makefiles

3 major OS’es (Unix, Windows, Mac OS X) 32 and 64 bit little and big endian

10 different compilers gcc with many flavors on nearly all

platforms, Solaris: CC4,5, HPUX: aCC, SGI: CC, AIX:

xlC Alpha: CXX6, Windows: VC++6,7 Intel icc on Linux

37 Makefiles


ROOT Downloads

333,000 binaries

download

1,500,000 clicksper month

140,000user guides

1300 userssubscribed to

roottalk


The ROOT Project Evolution

1995 2000 2005

ROOT 0.5

ROOT 1.0

ROOT 2.0

ROOT 3.0

LEP,HERA,SPS

RHIC, FNAL/RUN II, Babar,KEK

LHCLarge Hadron Collider

functionality

ROOT 4.0ROOT 5.0


The ROOT Web Site

http://root.cern.ch General Information and News

Download sources and binaries

HowTo’s & Tutorials

User Guide & Reference Guide

Roottalk Digest & Forum

Printed copies of the user guide are available from

Ilka Antcheva, room 32-R-C13


Fundamental features of an Object-Oriented Data Analysis Framework

Object Persistency must be simple for simple applications:

histograms, simple simulations, test beams must be efficient for Perabytes of data

User Interface, must have command and script mode interpreted code <===> compiled code GUI and browsers

Class Dictionary is the vital element


ROOT: Framework & Library

User classes

user can define new classes interactively

either via calling API or sub-classing API

these classes can inherit from ROOT classes

Dynamic linking

interpreted code can call compiled code

compiled code can call interpreted code

macros can be dynamically compiled & linked

This is the normaloperation mode

Interesting featurefor GUIs,

config files, etc.

Script Compilerroot > .x file.C++


ROOT Library Structure ROOT libraries are a layered structure The CORE classes are always required (support for RTTI,

basic I/O and interpreter) The optional libraries (you load only what you use).

Separation between data objects and the high level classes acting on these objects. Example, a batch job uses only the histogram library, no need to link histogram painter library

Shared libraries reduce the application link time Shared libraries reduce the application size ROOT shared libraries can be used with other class libraries Shared libraries are mostly loaded via the plug-in manager


The ROOT Libraries Over 1000

classes

1,350,000 lines of code

CORE (12 Mbytes)

CINT (2 Mbytes) Green libraries

linked on demand via plug-in manager (only a subset shown)


C++ interpreter Data analysis and visualization tools 2D and 3D graphics, Postscript, PDF,

LateX Geometrical modeller Object persistency and Trees GUI Online services

Quick Overview


CINT CINT is a C and C++ interpreter Written by Masaharu Goto and available under an

Open Source license It implements about 95% of ANSI C and 95% of

ANSI C++ It is robust and complete enough to interpret

itself (85000 lines of C++) Has good debugging facilities In most cases it is faster than tcl, perl, python


CINT in ROOT

CINT is used in ROOT: as command line interpreter as script interpreter to generate class dictionaries to generate function/method calling

stubs The command line, script and

programming language become the same Large scripts can be compiled for optimal

performance


The dictionary provided by CINT is the nerve-centre of ROOT

The dictionary provides the Run Time Type Information (RTTI)

The rootcint program is used to parse the classes and generate the dictionaries

RTTI is used by the I/O services By definition the interpreter is based on it The GUI context sensitive menus The browsers, object inspectors The ROOT utilities to draw class diagrams The html documentation generator The signal/slot mechanism

The CINT Dictionary


CINT as Interpreter

CINT is used as command line interpreter:

And as script interpreter:

root[0] for (int i = 0; i < 10; i++) printf(“Hello\n”)root[1] TF1 *f = new TF1(“f”, “sin(x)/x”, 0, 10)root[2] f->Draw()

bash$ cat script.C{ for (int i = 0; i < 10; i++) printf(“Hello\n”); TF1 *f = new TF1(“f”, “sin(x)/x”, 0, 10); f->Draw();}root[0] .x script.C


A Data Analysis & Visualization Tools


Graphics: 1,2,3-D functions


Full LateX support

on screen and

postscript

TCurlyArcTCurlyLineTWavyLine

and other building blocks for Feynmann diagrams

Formula or

diagrams can beedited

with the mouse


Alice 3 million nodes


ROOT I/O : An Example

TFile f(“example.root”,”new”);

TH1F h(“h”,”My histogram”,100,-3,3);

h.FillRandom(“gaus”,5000);

h.Write();

TFile f(“example.root”);

TH1F *h = (TH1F*)f.Get(“h”):

h->Draw();

f.Map();

Program Writing

Program Reading

20010831/171903 At:64 N=90 TFile 20010831/171941 At:154 N=453 TH1F CX = 2.0920010831/171946 At:607 N=2364 StreamerInfo CX = 3.2520010831/171946 At:2971 N=96 KeysList 20010831/171946 At:3067 N=56 FreeSegments 20010831/171946 At:3123 N=1 END

demoh.C

demohr.C


A Root file pippa.rootwith two levels of

directories

Objects in directory/pippa/DM/CJ

eg:/pippa/DM/CJ/h15


Memory <--> TreeEach Node is a Branch in the Tree

0123456789101112131415161718

T.Fill()

T.GetEntry(6)

T

Memory


Example Writing a Treevoid demoe(int nevents) { //load shared lib with the Event class gSystem->Load("$ROOTSYS/test/libEvent"); //create a new ROOT file TFile f("demoe.root",”new"); //Create a ROOT Tree with one single top level branch int split = 99; //try also split=1 and split=0 int bufsize = 16000; Event *event = new Event; TTree T("T","Event demo tree"); T.Branch("event","Event",&event,bufsize,split); //Build Event in a loop and fill the Tree for (int i = 0; i < nevents; i++) { event->Build(i); T.Fill(); } T.Print(); //Print Tree statistics T.Write(); //Write Tree header to the file

}

All the examples can be executedwith CINTor the compiler

root > .x demoe.Croot > .x demoe.C++


Example Reading a Treevoid demoer() { //load shared lib with the Event class gSystem->Load("$ROOTSYS/test/libEvent"); //connect ROOT file TFile *f = new TFile("demoe.root"); //Read Tree header and set top branch address Event *event = 0; TTree *T = (TTree*)f->Get("T"); T->SetBranchAddress("event",&event); //Loop on events and fill an histogram TH1F *h = new TH1F("hntrack","Number of tracks",100,580,620); int nevents = (int)T->GetEntries(); for (int i = 0; i < nevents; i++) { T->GetEntry(i); h->Fill(event->GetNtrack()); } h->Draw();

}

Rebuilds the full eventin memory


8 Branches of T

8 leaves of branchElectrons

A double-clickto histogram

the leaf


The Tree Viewer & Analyzer

A very powerful classsupporting

complex cuts,event lists,

1-d,2-d, 3-d viewsparallelism


Tree Friends

0123456789101112131415161718

0123456789101112131415161718

0123456789101112131415161718

Public

read

Public

read

User

Write

Entry # 8


Basic GUI Widgets


GUI Example


ROOT now used in many DAQ environments Timers, shared memory, sockets GUI & event display Macros for rapid prototyping Histogramming Thread support

ROOT in Online


General Remarks In 1995, we had planned less than 50% of ROOT 2005.

importance of dictionary, RTTI automatic Schema Evolution effort in GUI online requirements (threads, timers, sockets, etc.)

Development of a system is driven by: ideas from authors ideas from users new ideas and techniques in computing OS development, in 1995, push for Windows, Linux not here language developments (e.g. template support, exception handling, Java) cooperation with other systems (e.g. Oracle, Corba, Qt, etc.) manpower

Users expect stable and working systems. Quality of a system should

improve with time. Often in contradiction with major new developments.


ROOT: an Evolving System

The ROOT system has been in continuous development since 1995 surviving major changes, major enhancements and an ever increasing number of users.

In the same way that ROOT 2005 is far from the original ROOT 1995, we expect that ROOT 2010 will include many contributions reflecting the continuous changes and new ideas in the field of computing.

This implies a strong cooperation between software developers and the software users.

ROOT is being developed in very close cooperation with a cloud of software developers in science but also in the commercial world.


Playing with ROOT on lxplus

Set the environment variables export

ROOTSYS=/afs/cern.ch/sw/root/v5.02.00/slc3_gcc3.2.3/root

export LD_LIBRARY_PATH=$ROOTSYS/lib:$LD_LIBRARY_PATH

export PATH=$ROOTSYS/bin:$PATH Copy the ROOT tutorials

cd $HOME cp $ROOTSYS/tutorials . cd tutorials

Run ROOT root


Playing with ROOT on a PC Import a binary tar file from:

http://root.cern.ch/root/Version502.html E.g.: Intel x86 Linux for SLC 3 and gcc 3.2.3, version

5.02/00 Untar the file in your home directory

cd $HOME tar zxvf root_v5.02.00.Linux.slc3.gcc3.2.3.tar.gz

Set the environment variables export ROOTSYS=$HOME/root export LD_LIBRARY_PATH=$ROOTSYS/lib:$LD_LIBRARY_PATH export PATH=$ROOTSYS/bin:$PATH

Go to the ROOT tutorials cd $HOME cp $ROOTSYS/tutorials . cd tutorials

Run ROOT root


My first session

root [0] 344+76.8(const double)4.20800000000000010e+002root [1] float x=89.7;root [2] float y=567.8;root [3] x+sqrt(y)(double)1.13528550991510710e+002root [4] float z = x+2*sqrt(y/6);root [5] z(float)1.09155929565429690e+002root [6] .q

root

root

root [0] try up and down arrows

See file $HOME/.root_hist


My second session

root [0] .x session2.Cfor N=100000, sum= 45908.6

root [1] sum(double)4.59085828512453370e+004

Root [2] r.Rndm()(Double_t)8.29029321670533560e-001

root [3] .q

root

{ int N = 100000; TRandom r; double sum = 0; for (int i = 0; i < N; i++) { sum += sin(r.Rndm()); } printf("for N=%d, sum= %g\n",N,sum);}

session2.C

unnamed macroexecutes in global scope


My third session

root [0] .x session3.Cfor N=100000, sum= 45908.6

root [1] sumError: Symbol sum is not defined in current scope*** Interpreter error recovered ***

Root [2] .x session3.C(1000)for N=1000, sum= 460.311

root [3] .q

root

void session3 (int N=100000){ TRandom r; double sum = 0; for (int i = 0; i < N; i++) { sum += sin(r.Rndm()); } printf("for N=%d, sum= %g\n",N,sum);}

session3.C

Named macroNormal C++ scope

rules


My third session with ACLIC

root [0] gROOT->Time();root [1] .x session4.C(10000000)for N=10000000, sum= 4.59765e+006Real time 0:00:06, CP time 6.890

root [2] .x session4.C+(10000000)

for N=10000000, sum= 4.59765e+006 Real time 0:00:09, CP time 1.062

root [3] session4(10000000)for N=10000000, sum= 4.59765e+006Real time 0:00:01, CP time 1.052

root [4] .q

#include “TRandom.h”void session4 (int N) { TRandom r; double sum = 0; for (int i=0;i<N;i++) { sum += sin(r.Rndm()); } printf("for N=%d, sum= %g\n",N,sum);}

session4.C

File session4.CAutomatically compiled

and linked by thenative compiler.

Must be C++ compliant


Macros with more than one function

root [0] .x session5.C >session5.logroot [1] .q

void session5(int N=100) { session5a(N); session5b(N); gROOT->ProcessLine(“.x session4.C+(1000)”);}void session5a(int N) { for (int i=0;i<N;i++) { printf("sqrt(%d) = %g\n",i,sqrt(i)); }}void session5b(int N) { double sum = 0; for (int i=0;i<N;i++) { sum += i; printf("sum(%d) = %g\n",i,sum); }}

session5.C

.x session5.Cexecutes the function

session5 in session5.C

root [0] .L session5.Croot [1] session5(100); >session5.logroot [2] session5b(3)sum(0) = 0sum(1) = 1sum(2) = 3

root [3] .q

use gROOT->ProcessLineto execute a macro from a

macro or from compiled code


Interactive Demo

You can import the tar file with all demos fromftp://root.cern.ch/root/SummerStudents2005.tar.gz

root summershow.C

You can find more demos, examples, tests at

$ROOTSYS/tutorials

$ROOTSYS/test

$ROOTSYS/test/RootShower

Documents

Introduction to ROOT1 Summer Students Lecture 20 July 2005 [email protected] Introduction to ROOT