Working with ATLAS offline software at U.S. ATLAS Tier 1 Center

The related topics:

• Atlas Software Releases Installation and How To Use Them
• Code Repositories
• BNL Mirror of ATLAS Pacman Cache
• Data Storage
• Information And Help Resources

Accounts, file systems, computers

Please refer to the Tier I Computing Facility (ACF) help pages for details on accounts, file systems, and ACF computers. Here is a short summary.

• In order to obtain a new computer account at the ACF a prospective user has to read and agree to the Brookhaven National Laboratory computer user agreement. Your supervisor may be asked to confirm the request for a new account. If he sends the confirmation message simultaneously with your request then the account will be probably set faster.
• The computers at ACF are behind firewall. For access, first you need to ssh to the gateway machine atlasgw.bnl.gov. Then you can log into interactive Linux farm nodes, acas0XXX.usatlas.bnl.gov farm nodes (XXX is a 3-digit number, for example 001 - 009). There is also the general purpose interactive Linux workstation at atlas00.usatlas.bnl.gov with larger selection of programs (e.g. firefox, xfig that are not installed on acas machines).
• Many US ATLAS users have CERN computing accounts. Read here how to get them (waiting time is one week or more).
• After login the user is in his NFS home directory with the path stored in $HOME variable. Home directories are backed up but of rather limited size (500 MB is standard). There is a scratch (not backed-up) NFS system at /usatlas/scratch/<username> for temporary file storage. When the scratch area becomes full the older and larger files are automatically purged. ACF has also established AFS cell, /afs/usatlas.bnl.gov, for sharing files with remote institutions. Users have personal AFS areas at /afs/usatlas.bnl.gov/users/<username> and all ATLAS software is installed on AFS.

Organization of ATLAS software

ATLAS software is organized in large releases (more than 1000 packages). New stable development releases of atlas software are produced in three weeks intervals (there are also nightly builds for checking the latest submissions, but beginners are not encouraged to use them). The names of stable ATLAS releases are 1X.Y.Z, where X,Y,Z=0-9. The "production" ATLAS releases have Y=0, all other releases are "development". There are also releases of patches named as 1X.0.Z.KL and Physics Analysis releases named as 1X.0.Z.KL.MN (X,Z,K,L,M,N=0-9). ATLAS software releases depend on many external packages (about 50). The main OO framework, ATHENA, is based on the GAUDI architecture that is technically also an external package.

At the U.S. ATLAS Tier I Computing Facility the stable and selected nightly ATLAS software releases are downloaded from pacman distribution kits at /afs/usatlas.bnl.gov/software/downloads/releases/. In addition ATLAS production releases are installed on NFS by OSG group at /usatlas/projects/OSG/atlas_app/atlas_rel Further details are available at our page ATLAS software releases and how to use them .

An ATLAS software release consists of an install area ( InstallArea ) and directories of packages. An install area contains references (soft links) to binaries, includes and share files dispersed in the release tree. ATLAS releases are managed by CMT release tool. The packages are organized according to CMT principles and can be simple packages (with no subpackages) or containers of simple packages and/or subcontainers. A CMT package consists of areas with sources, binaries, and cmt directory with CMT configuration (usually stored in single requirements file). Theoretically CMT allows multiple versions of one package in the release, however in ATLAS releases all packages have a single version.

Relevant links

• U.S. ATLAS Physics, Software and Computing top page
• How to get help with ATLAS software
• The ATLAS Workbook - comprehensive information for ATLAS software users on wiki
• Additional information for ATLAS software users (complementary to ATLAS Workbook). This page contains many useful recipes and workarounds.
• U.S. ATLAS Tier I Computing Facility.
• project NightliesUploadCVMFS
• More links from U.S. ATLAS Software Infrastructure

-- AlexUndrus - 05 Nov 2010