ROOT

1
ROOT

• An object oriented HEP analysis framework.
• Day 2
• http//www-pat.fnal.gov/root/
• The ROOT system website is at http//root.cern.ch
  /

2
Day 2

• Last time
• GUI, Command line
• Today
• Command Line (CINT)
• Scripts (CINT ACLiC)
• Exercises
• Functions and Fitting
• TreeViewer

3
Command line

• Environment Settings
• Command types
• CINT Commands
• Global Variables
• TObject

4
Environment Settings

• Environment setting file
• ROOTSYS/etc/system.rootrc
• looks first in current directory for .rootrc
• second in HOME/.rootrc
• third in ROOTSYS/etc/system.rootrc
• Find the current settings
• root gEnv-gtPrint()

5
Environment Settings (cont.)

• The .rootrc file
• The Macro Path
• Unix..Root.MacroPath.(HOME)/myRootMacros
• Options in .rootrc
• Root.ShowPath false
• History File
• HOME/.root_hist
• Automatically Executing Macros
• rootlogon.C
• rootlogoff.C
• rootalias.C

6
Command Line Options

• gt root -/?
• Usage root -l -b -n -q file1.C ...
  fileN.C
• Options
• -b run in batch mode without graphics
• -n do not execute logon and logoff macros as
  specified in .rootrc
• -q exit after processing command line macro
  files
• -l do not show splash screen

7
Three Types of Commands

• CINT commands start with .
• root0.?
• this command will list all the CINT commands
• root1.X filename
• load filename and execute function filename
• root2.L filename
• load filename
• SHELL commands start with .! for example
  root3 .! ls

8
Three Types of Commands

• 3. C syntax (almost)
• root 0 TBrowser b new TBrowser()or
• root 0 TBrowser b new TBrowser()
• The optional Semicolon
• Leave off the semicolon to see the return value
  of the command.
• root 0 235 // show return value
• (int)28
• root 1 235 // no return value root 2

9
Command Line Help

• Use the Tab feature to get help
• root 0 b new TB ltTABgt
• root 1 b new TBrowltTABgt
• root 2 b new TBrowser(ltTABgt
• Find List of Methods
• Find Parameter list

10
Coding Conventions

• Based on Taligent
• Classes begin with T TTree, TBrowser
• Non-class types end with _t Int_t
• Data members begin with f fTree
• Member functions begin with a capital Loop()
• Constants begin with k kInitialSize, kRed
• Static variables begin with g gEnv
• Static data members
  begin with fg fgTokenClient

11
CINT Types
12
CINT Extensions to C

• 1. Declaration can be omitted
• f new TFile("Example.root")
• 2. "." notation rather than "-gt" f.ls()
• 3. Search for an object by its name
• TH1F smallHisto new TH1F
• ("small","fPx 100",100,-5,5)
• small-gtDraw()
• Warning These will not work in compiled code!

13
CINT Commands

• expression evaluates the expression
• root3 34
• (int)12
• .files show loaded source files
• .class name show class definition
• .g prints all objects in the root session
• .ls ls on current directory
• .pwd list the current directory, canvas, and
  style.

14
Demo on CINT Commands

• .class
• root 0 .L ROOTSYS/test/libEvent.so
• root 1 .class Event
• .g
• root 2 .g...
• 0x104c7560 Event e , size56
• 0x0 private Int_t fNtrack
• 0x0 private Int_t fNseg
• 0x0 private Int_t fNvertex
• ...

15
CINT Multi-line Command

• Start with "" For example

root
end with ''gt Int_t j 0
end with ''gt for (Int_t i 0 i lt 3
i) end with ''gt
end with ''gt j j i
end with ''gt cout ltlt"i "
ltltiltlt", j " ltltjltltendl end with ''gt
end with ''gt
i 0, j 0 i 1, j 1 i 2, j 3
16
Global Variables

• gRandom
• gRandom-gtGaus(1,2)
• You can replace the random generator with your
  owndelete gRandomgRandom new TRandom2(0)
  //seed0
• gFile
• gFile-gtGetName()
• gDirectory
• gDirectory-gtGetName()
• gSystem
• gSystem-gtHostName()

17
gROOT

• global ROOT session object
• gROOT-gtGetListOflt list type gt()
• gROOT-gtLoadMacro()
• gROOT-gtTime()
• gROOT-gtProcessLine()

18
gROOT-gtFindObject()

• TH1F smallHisto new TH1F
• ("small","fPx 100",100,-5,5)
• "small" is the Object Name
• gROOT-gtFindObject("small")
• (class TObject)0x104c7528
• "smallHisto" is the Variable Name
• gROOT-gtFindObject("smallHisto")
• (class TObject)0x0 // null pointer
• FindObject needs the Object Name.

19
gROOT-gtFindObject()

• FindObject returns a pointer to TObject.
• This generates an error
• gROOT-gtFindObject("small")-gtGetBinContent(2)
• This is OK
• gROOT-gtFindObject("small")-gtClassName()
• TH1F histo(TH1F) gROOT-gtFindObject("small")
• histo-gtGetBinContent(2)

20
gROOT-gtFindObject() cont.

• Due to CINT magic this is also OK
• TH1F smallHisto new TH1F
• ("small","fPx 100",100,-5,5)
• small-gtGetBinContent(2)
• CINT implicitly executes a FindObject("small")
• Casts it to the correct class
• Creates a variable called "small" of the correct
  class
• Warning This will not work in compiled code!

21
Demonstration FindObject

• FindObject()
• root 3 f TFile("Example.root")
• root 4 .ls
• root 5 gROOT-gtFindObject("myTree")
• root 6 myTree

22
TObject The Mother of all Root objects

• Defines protocol and default behavior for all
  objects in ROOT.
• I/O
• Drawing/Painting
• TObjects can be stored in collection classes.
• Introspection, Reflection, Runt Time Type
  Identification

23
TObject RTTI

• RTTI the ability of a class to reflect upon
  itself or to "look inside itself" at run time.
• TClass implement RTTI
• To get the TClass from a TObject descendent
  obj-gtClass()
• TClass can find the
• Methods
• Data members
• Base classes

24
Summary (Command Line)

• Environment Settings
• Command types
• CINT Commands
• Global Variables
• TObject

25
Writing Scripts

• Named and Un-named Scripts
• Debugging
• ACLiC

26
Scripts

• Un-named Script
• Start with "" and end with ""
• All variables are in the global scope
• No class definitions
• No function declarations
• No parameters
• Named Script
• C functions
• Scope rules follow standard C
• Function with the same name as the file is
  executed with a .x
• Parameters
• Class definitions (derived from a compiled class
  at your own risk)

27
Scripts Examples

• Un-named Script hello.C
• cout ltlt "Hello" ltlt endl
• Named Scriptsay.C
• void say(char what "Hello")
• cout ltlt what ltlt endl
• Executing the Named Script
• root 3 .x say.C
• Hello
• root 4 .x say.C("Hi there")
• Hi there

28
Resetting the Environment

• gROOT-gtReset()
• Calls destructors of all objects created on the
  stack
• Objects on Heap are not deleted, but pointer
  variable is disassociated

29
Debugging Stepping

• .s set the step mode to step into
  function
• .S set the step mode to go over
  function or loop
• .e continue to end of the function
• .c continue to next breakpoint
• .c 45 continue to line 45
• .p ltvargt print the value of var

30
Debugging Breakpoints

• .trace MyClass prints the executing
  code to window
• .deltrace MyClass removes the trace
• .break MyClass breaks at each
  method of MyClass
• .delbreak MyClass removes the break
• .b 34 sets a break point
  at line 34
• .db 34 removes the break
  point at line 34

31
Debugging Inspecting

• DrawClass() Graphic list of methods
  
• including ancestors
• Inspect() Draw the current
  contents of an object
• Dump() Lists the current
  contents of an object
• gDebug 1 Prints debugging
• information

32
Tracking Memory Leaks

• Counting Objects and Memory use
• In the .rootrc or system.rootrc file
• Root.MemStat 1
• Root.ObjectStat1
• Print the Object count and Memory use
• gObjectTable-gtPrint()

33
Tracking Memory Leaks

• Example output
• Before .x FirstContour.C
• count on heap size
  total size heap size
• Total 1,079 1,046 3,160
  49,992 45,824
• After
• Total 1,783 1,749 17,920 118,912
  114,568
• Put gObjectTable-gtPrint() before and after code
  segment in your script to find memory leaks.

34
ACLiC Automatic Compiler of Libraries for CINT

• Use an external compiler to create a shared
  library from a macro.
• Use
• root 0 .L MyMacro.C
• Always recompile
• root 0 .L MyMacro.C
• Recompile as needed

35
ACLiC Use

• Restriction can not use path name with .L
• .L ../root_base/MyMacro.C
• Instead do
• gSystem-gtcd("../directory")
• gSystem-gtCompileMacro("MyMacro.C")
• Options are
• k keep the shared library after the session
  end.
• f force recompilation.
• To set the Include path
• .include "-IHOME/mypackage/include"

36
ACLiC Advantages

• Advantages
• syntax checking
• about five times faster
• full C feature set
• Disadvantage
• On KCC, you can load each C shared library
  only once

37
ACLiC Demo

• .L ScriptCompilerDemo.C
• root 0 gROOT-gtTime()
• root 1 .L ACLiCDemo.C
• root 2 .files
• root 3 Demo()
• Compare performance with CINT
• root 0 gROOT-gtTime()
• root 1 .L ACLiCDemo.C
• root 3 Demo()

38
Summary (Scripts)

• Named and Un-named Scripts
• Debugging
• ACLiC

39
Getting started with the Exercises

• Go to http//patwww.fnal.gov/root/class/Setup.htm
  for setup instructions using Reflection and ssh
  on fcdfsgi2 and d0mino and minos1.
• Find the exercises on line at
• http//patwww.fnal.gov/root/class/exercises.htm

40
Exercise Overview

• Session A
• Use ROOT command line
• Write a named and un-named script
• Use the GUI to create objects and change their
  attributes
• Save your canvas to a PostScript file
• Fit a graph
• Session B
• Fit and rotate a histogram
• Use the Object Browser and the Tree Viewer
• Make a profile and contour graphs
• Build an event list from a cut
• Fill a histograms with random numbers
• Use ACLiC

41
Exercise Session C

• Session C
• Study an example analysis from DESY
• Learn about the TTreeMakeSelector method to
  automatically create a class that loops over each
  entry in a tree.
• Save and retrieve a canvas to and from a ROOT
  file
• Compute the integral of a histogram
• Compute the integral of a function within a range

42
Solutions to the Exercises

• http//patwww.fnal.gov/root/class/solutions.htm

43
ROOT contacts at Fermi

• Philippe Canal , x2545 pcanal_at_fnal.gov
• Suzanne Panacek, x8334 spanacek_at_fnal.gov
• Jeff Kallenbach, x2210
• jeffk_at_fnal.gov

44
Mailing Lists

• the ROOT mailing list
• roottalk_at_root.cern.ch
• archives
• http//root.cern.ch/root/roottalk/AboutRootTalk.ht
  ml
• Fermilab mailing list
• about-root_at_fnal.gov
• archives
• http//listserv.fnal.gov/archives/about-root.html

45
Functions and Fitting

• Function Objects (TF1)
• Three constructors for TF1
• User Defined Functions
• Fitting
• Fit()
• Fitting with a user defined function
• Fitting subranges and combining functions
• Demonstration of background and signal function

46
Function Objects (TF1)

• Built in function objects
• see this link for a full list of built in
  functions
• http//root.cern.ch/root/html/TFormula.htmlTFormu
  laTFormula
• use the Fit Panel
• Creating your own function objects
• TF1, TF2, TF3
• Three Signatures for the TF1 constructor

47
TF1 Constructors

• 1. A C like expression using x with a fixed set
  of operators and functions defined in TFormula
• TF1 f1 new TF1("f1","sin(x)/x",0,10)
• f1-gtDraw()
• TF1 f2 new TF1("f2","f1 2",0,10)

48
TF1 Constructors (cont.)

• 2. Same as the previous TF1 with Parameters
• Call the constructor with parameter indices
• TF1 f1 new TF1
• ("f1","0 xsin( 1 x)",-3,3)See TFormula
  for valid expressions
• Set the parameters explicitly
• f1-gtSetParameter(0,10)f1-gtSetParameter(1,5)f1-
  gtDraw()

49
TF1 Constructors (cont.)

• 3. Use a defined function
• Define a functionDouble_t MyFunction(Double_t
  x, Double_t par) Float_t xx
  x0 Double_t val TMathAbs(par0sin(
  par1xx)/xx) return val
• TF1 constructor TF1 f1 new TF1("f1",MyFunction
  ,0,10,2)
• NOTE The 2 is the number of parameters in
  MyFunction.
• Set the parametersf1-gtSetParameters(2,1)

50
Fitting

• To fit a histogram
• TF1 fn1 new TF1
• ("f1","0 xsin(1x)",-3,3)
• f1-gtSetParameters(10,5)aHistogram-gtFit("f1")
  //name
• aHistogram-gtFit(fn1) // pointer

51
Fitting Example

• Step 1. Define the function
• Double_t MyFunction (Double_t x, Double_t par)
• Double_t arg 0
• if (par2) arg (x0 - par1)/par2
• Double_t fitval
• par0 TMathExp(-0.5argarg)
• return fitval

52
Fitting (cont.)

• Step 2. TF1 constructorTF1 aFunction new
  TF1("MyGaus", MyFunction, -5,5,3)
• Step 3. Set initial value of the
  parametersaFunction-gtSetParameters(5000,
  h-gtGetMean(), h-gtGetRMS())
• Step 4. Fit and draw the histogramh-gtFit("MyGaus"
  )

53
Fitting Sub-Ranges Example

• ROOTSYS/tutorials/multifit.C
• Define the range in the TF1 constructor.
• TF1 g1 new TF1("g1", "gaus", 85,95)
• By default, TH1Fit on the defined histogram
  range. Use "R" option in the Fit()
  method.h-gtFit("g1", "R")

54
Fitting Subranges
55
Fitting Subranges

• Define gaussian functions
• g1 new TF1("m1","gaus",85,95)
• g2 new TF1("m2","gaus",98,108)
• g3 new TF1("m3","gaus",110,121)
• total new
• TF1("mstotal","gaus(0)gaus(3)gaus(6)",85,125)
• From TFormula
• gaus(0) is a substitute for 0exp(-0.5((x-1
  )/2)2)
• and (0) means start numbering parameters at 0

56
Fitting Sub-Ranges

• Fit each range and get the parameter for "total"
• h-gtFit(g1,"R")
• h-gtFit(g2,"R")
• h-gtFit(g3,"R")
• g1-gtGetParameters(par0)
• g2-gtGetParameters(par3)
• g3-gtGetParameters(par6)
• total-gtSetParameters(par)
• h-gtFit(total,"R")

57
Signal and Background Demo
y(E) a1 a2E a3E2 AP (? / 2 ?)/(
(E-?)2 (?/2)2) background lorenzianPeak pa
r0 a1 par0 AP par1 a2 par1
? par2 a3 par2 ? fitFunction
background (x, par ) lorenzianPeak (x,
par3) par0 a1 par1 a2 par2
a3 par3 Ap par4 ? par5 ?
58
Fitting Demo

• Look at
• FittingDemo.C
• Unnamed Macro
• fitf.C
• Named Macro
• Run FittingDemo.C
• More info on fitting
• http//root.cern.ch/root/html/examples/fit1.C.html
  
• http//root.cern.ch/root/html/examples/myfit.C.htm
  l
• http//root.cern.ch/root/html/examples/backsig.C.h
  tml

59
Summary Fitting and Functions

• Functions Objects (TF1)
• Three constructors for TF1
• User Defined Functions
• Fitting
• Fit()
• Fitting with a user defined function
• Fitting sub ranges and combining functions
• Demonstration of background and signal function

60
The Tree Viewer Overview

• Drawing Histograms
• Using Cuts
• Lego Plots
• Creating new Variables
• Saving the Canvas

61
The Tree Viewer

• root myTree-gtStartViewer()
• Contents
• XYZ
• Cut
• Scan
• Expressions
• Variables (leaves)
• Draw option
• Recording commands
• Histogram
• Range Selector
• IList/OList

62
Drawing Two Histograms

• Double click on one variable
• Select Superimpose option
• Double click on another variable

63
Adding Weight
Add a Weight xmain lt 0
64
2D Lego Plots

• Draw xmain vs. xs1
• Rotating the lego plot

65
Creating a variable

• 1. Create New Expression

• 2. Set the name and expression
• 3. Double click to draw it

66
More Features

• Record
• Command is recorded in history file
  (HOME/root_hist)
• Is printed on the command line
• Scan
• 1) Drag and drop variables to scan box
• 2) Redirect output to a file
• Saving and recovering a Session
• 1) Save the current cuts, expressions into
  treeviewer.C
• 2) Read session back

67
Saving the Canvas

• The save options
• Postscript
• gif
• ROOT file
• Macro
• Save as a ROOT file
• Open the saved ROOT file (c1.root) and draw the
  canvas
• root2 gt c1.Draw()

68
Summary (TreeViewer)

• Drawing a Two Histogram
• Adding Weight
• Lego Plots
• Creating a variable
• More Commands
• Saving a Canvas