Writing a task in AliPhysics Some basic c++, ALICE tasks, tips and conventions

163 Pages·2017·7.82 MB·English

Writing a task in AliPhysics
Some basic c++, ALICE tasks, tips and conventions
Redmer Alexander Bertens
University of Knoxville, Tennessee
RedmerAlexanderBertens-Nov22017-slide1of93 Writingatask
What’s the aim?
At the end of this session, you’ll understand what happens in your
task (what is a ClassDef(), what //-> means, etc...)
As we’ll go along, we’ll explore (very) basic but also a bit more advanced
concepts
The full source code is attached to the agenda, I’ll just show snippets
I’ll assume that AliPHYSICS is running on your machine
Before starting
What are we gonna do today?
Basic goal: showing you how to write and run a minimal task to do
analysis
No physics here - just getting it up and running
RedmerAlexanderBertens-Nov22017-slide2of93 Writingatask
Before starting
What are we gonna do today?
Basic goal: showing you how to write and run a minimal task to do
analysis
No physics here - just getting it up and running
What’s the aim?
At the end of this session, you’ll understand what happens in your
task (what is a ClassDef(), what //-> means, etc...)
As we’ll go along, we’ll explore (very) basic but also a bit more advanced
concepts
The full source code is attached to the agenda, I’ll just show snippets
I’ll assume that AliPHYSICS is running on your machine
RedmerAlexanderBertens-Nov22017-slide2of93 Writingatask
you can find this talk (and full tutorial) as well as previous ones at the
analysis tutorial webpage - including recordings of the sessions
RedmerAlexanderBertens-Nov22017-slide3of93 Writingatask
spot the differences
.
.
.
RedmerAlexanderBertens-Nov22017-slide4of93 Writingatask
Overview:
- some words on classes
- writing your task
- running it (local, grid, trains)
- workflow and troubleshooting
- ROOT’s //! and streamers
- coding conventions
- pointers and memory management
... most likely we’ll have time for 50% of
the slides ...
RedmerAlexanderBertens-Nov22017-slide5of93 Writingatask
RedmerAlexanderBertens-Nov22017-slide6of93 Writingatask
A bit abstract, but not so difficult when you see it
1 class Rectangle
2 {
3 private:
4 int width, height;
5 public:
6 Rectangle(int,int);
7 int GetArea() {return height * width;}
8 }
Classes
Code in ROOT / AliROOT / AliPhysics has the form of classes, generally
one class per file
Our analysis task will also be a c++ class
A class contains both variables and functions (called ‘methods’) as
members
Often the member variables must be accessed through the methods
RedmerAlexanderBertens-Nov22017-slide7of93 Writingatask
Classes
Code in ROOT / AliROOT / AliPhysics has the form of classes, generally
one class per file
Our analysis task will also be a c++ class
A class contains both variables and functions (called ‘methods’) as
members
Often the member variables must be accessed through the methods
A bit abstract, but not so difficult when you see it
1 class Rectangle
2 {
3 private:
4 int width, height;
5 public:
6 Rectangle(int,int);
7 int GetArea() {return height * width;}
8 }
RedmerAlexanderBertens-Nov22017-slide7of93 Writingatask
This avoids having to repeat common code for all classes
but can sometimes make understanding the code a bit tricky
Classes and inheritance
Classes are nice, because they can be derived from one-another
CRectangle is derived from base class CPolyogon, and inherits its
members
RedmerAlexanderBertens-Nov22017-slide8of93 Writingatask