LHCb Software At Nikhef: Prepare for Workshop 22-24 June 2009

Introduction

The Bfys workshop will not take place at a high energy physics lab. Wireless connection is available, but for the hands-on work, we will not rely on that. Instead we provide two solutions:

1) Connect with ethernet cable to a computer/server. (See: Running on Workshop Server )

2) Install and configure virtual machine on your laptop, "CernVM". (How to install)

(This will give the possibility to run LHCb software locally, very much as if you logon to a computer inside your laptop...)

We ask you to try to run an example job on the server using your laptop, before the workshop starts on Monday. (See Running on Workshop Server)

In addition - to familiarize with the LHCb software jargon - we ask you to read through the following pages too:

1) Python Basics

2) Bender Tutorial (twiki) Tutorial (pdf)

3) Gaudi Basics (twiki)

Running at Nikhef

Logon at Nikhef

ssh user@ribble.nikhef.nl
ssh stbc-16   (on stoomboot)

Set the environment

Here we set the environment for DaVinci, but it could also another LHCb application, like Bender or Panoramix.

mkdir cmtuser
cd cmtuser
source /project/bfys/lhcb/sw/setup.sh   # for sh, bash, ksh, zsh
source /project/bfys/lhcb/sw/setup.csh  # for csh, tcsh
SetupProject --build-env DaVinci v23r1 # makes a DaVinci_v23r1 directory if one doesn't already exist
SetupProject DaVinci v23r1 # exports environment variables to the shell

(NB: zsh-users should add 'setopt SH_WORD_SPLIT' to their .zshrc )

Running on Workshop Server

Logon to server

Linux:

ssh -Y u01@192.16.186.107    (# Available usernames: u01 - u15)
Password: (LHCb psswrd)

Windows:

Make sure you have Exceed running
ssh to 192.16.186.107       (# Available usernames: u01 - u15)
Password: (LHCb psswrd)

Setup Environment

(At startup, the script /opt/LHCb/LbLogin.sh is executed for all users. It sets up the necessary environment.)

Each of the user accounts has the MicroDSTExample installed. To run it:

SetupProject DaVinci v23r1
cd $MICRODSTEXAMPLEROOT/python

# Run over events:
python -i MicroDSTReadingExample.py --input /opt/LHCb/data/SeqDC06selBs2JpsiPhiWithMC_50.0_Kevt_NoPVReFit.dst

Running on a virtual machine on your very own laptop

This assumes you have successfully installed a CernVM on your computer. The installation varies between Windows, Mac OS and Linux, so see section further down for instructions on how to set it up. It also assumes you have set up basic login scripts, and installed AFS, X11R6, CVS and SVN if necessary. Also note that you have to run an application like DaVinci, Bender or Panoramix at least once while connected to the network in order to cache the necessary software.

Log onto your CernVM

This could mean starting the virtual machine and CernVM, starting it and logging in "remotely" from a terminal (Linux, Mac) or Exceed (Windows). Linux/Mac login

ssh -Y -p 2222 CernVMUserName@localhost

Windows login

Start exceed
Start ssh
Connect to vm with ssh to 192.168.204.128
     (Your number might be different!)
     (fink tunnel x11 connections in ssh!)

AFS access

If you need access to CERN AFS areas,

klog user@CERN.CH

Where user is your CERN AFS username. Note the UPPER CASE for the domain name. Be careful: Never do: ls /opt/ !! (It could start caching all atlas software...).

Set the environment

This is the same as in the remote login to Nikhef, except that the LHCb environment should be set when you log in if you have set up your CernVM correctly.

SetupProject --build-env DaVinci v23r1 # makes a DaVinci_v23r1 directory if one doesn't already exist
SetupProject DaVinci v23r1 # exports environment variables to the shell

The main difference here is that if you do not have the necessary software installed, CernVM will pull it and cache it for you. So the first time you do this you should have an interned connection.

Running over some events on a DST or MicroDST

After the environment has been set (either by remote login to Nikhef or CERN, or in the local CernVM on your laptop, we can start some simple analysis:

Get a nice package full of example scripts (new Bender Examples package exists too...)

If you haven't already got an examples package, get it, as you might need to perform modifications to some of the scripts. This has to be done when you have access to the internet.

getpack -p anonymous Ex/MicroDSTExample v2r5

cd ~/cmtuser/DaVinci_v23r1/Ex/MicroDSTExample/scripts
python -i MicroDSTReadingExample.py --input /data/bfys/h71/Workshop/SeqDC06selBs2JpsiPhiWithMC_50.0_Kevt_NoPVReFit.dst

Plot some of the histograms made by the script

>>> massPlots[443].plot()
>>> massPlots[531].plot()
>>> massResPlots[531].plot()
>>> propTimePlots[531].plot()
>>> Ctrl-D

Some more examples, using Gaudi or Bender environments and example scripts. Note we run them directly without getpacking them.

SetupProject Gaudi v21r0
python $GAUDIEXAMPLESROOT/python/HistoEx.py
SetupProject Bender v12r0
cd $BENDEREXAMPLEROOT/python/BenderExample/
./Phi.py

Introduction to Python

It is important that attendees make themselves familiar with the python programming language, at least at the level of writing simple scripts.

Python Basics

Extensive tutorial: Tutorial

Cheat Sheet: Cheat Sheet

Example: myfirst.py

Execute:
python myfirst.py