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Computing Technical Design Report
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Computing Technical Design Report
The ATLAS Computing Organization was completely revised at the beginning of 2003 in order to adapt it to the current needs of the Software & Computing Project. The basic principles of the organization are the following:
The bulk of the new structure (the Computing Management Board and the Software Project Management Board) was put in place during the first half of 2003; it was completed in autumn 2003 with the Operations, Data Challenges and Grid Management Board and in mid-2004 with the organization of the ATLAS-wide Database Project. The organization of the "Operations, Data Challenges and Grid" activity area was further revised in spring 2005. Figure 8-1 gives a pictorial view of the relations between the computing management bodies and major areas of activity.
After a collaboration-wide nomination procedure, the Computing Coordinator and the Software Project Leader are appointed by the ATLAS Spokesperson and confirmed by the ATLAS Collaboration Board for a two-year term. Re-appointments are possible but they require a two-thirds majority in the Collaboration Board.
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As it is important to keep a high level of communication at all levels with people involved in other ATLAS projects, their representatives are integrated in the Software & Computing Project organization and have dual reporting lines.
ATLAS Software & Computing Workshops take place four times per year (outside CERN approximately every 18 months). Workshops consist of plenary sessions at the beginning and the end of the week, and a number of parallel sessions in-between, where all activities and their integration issues are discussed. In addition, there are regular, more frequent meetings of all working groups.
The Computing Management Board (CMB) is the overall project management body. It is chaired by the Computing Coordinator. The CMB meets every two weeks to discuss all matters that involve cross-coordination between different activity areas, global planning and scheduling, high-level milestones, external constraints, relations with other ATLAS projects and with the LCG project.
The CMB consists of the coordinators of all Software & Computing activity areas and liaisons from (and to) other, related, ATLAS projects:
At the end of every Software & Computing workshop, four times a year, a joint meeting of the CMB and the SPMB (see Section 8.1.4 ) addresses global planning and scheduling issues.
The Computing Oversight Board (COB) is a subcommittee of the ATLAS Executive Board that oversees the coherence of computing activities across the boundaries of the TDAQ Project, Computing Coordination and Physics Coordination. The COB is chaired by the Deputy Spokesperson with responsibility for computing and comprises the Spokesperson and Deputies, the Computing Coordinator, the Software Project Leader, the TDAQ Project Leaders and the Physics Coordinator.
The International Computing Board (ICB) is the body that discusses the computing resources available to ATLAS, both hardware and manpower, and contributions from various collaborators to the ATLAS Computing project. As such the ICB receives and considers responses to effort and other computing reviews by the Computing Resource Review Board, CERN management and other such bodies.
It is the ATLAS forum for issues concerning the relationship between computing at the institutes and computing at CERN, and the means by which physicists in the institutes can contribute to the ATLAS computing project and analyse ATLAS data. The board considers and approves Software Agreements between Institutes and Funding Agencies and ATLAS, and also considers all disputes concerning their implementation.
It particularly concerns itself with issues regarding the construction and deployment of the worldwide computing infrastructure for ATLAS, and in particular relations between ATLAS and the LHC Computing Grid (LCG) project, and also network-based collaborative tools. As such, it appoints the ATLAS member of the LCG SC2 committee, and receives quarterly reports on the LCG project.
The ICB's remit also extends to those issues in the ATLAS software project that concern the outside institutes such as ease of installation of code, compilers, platforms, ease of use of the ATLAS suite at remote sites, licensing issues etc.
Given the importance of resources in its remit, the board is composed of delegated representatives of the funding agencies, as communicated by the National Contact Physicists, and a chairperson elected for a renewable two-year term by the voting members. The ICB has various ex-officio members to aid it in its work, namely the Computing Coordinator, Software Project Leader, Grid Coordinator(s), the ATLAS Spokesperson, Deputy Spokesperson and the ATLAS Resources Coordinator. The ATLAS-IT liaison and SC2 member appointed by the ICB are required to be in attendance.
The ICB meets four times per year, during Software and Computing Workshops.
The Software Project is led by the Software Project Leader. The mandate of the Software Project consists in the
The Software Project Management Board (SPMB) meets every two weeks to discuss coordination and software development planning issues. Its membership consists of:
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In addition to the SPMB, the Architecture Team, a consultative committee of core software development experts, advises the Software Project Leader on technical issues. Details of all software development activities are given in Chapter 3 of this document. Figure 8-2 gives a pictorial view of the areas of activity covered by the Software Project and its relations with the CMB and other computing management bodies.
The ATLAS Database and Data Management (DB/DM) Project was set up in spring 2004 to lead and coordinate all database activities within the ATLAS Collaboration, including those previously under the responsibility of the Software & Computing Coordination, Technical Coordination, the TDAQ Project and the Detector Projects.
The mandate of the DB/DM Project includes the development and deployment of the software necessary to operate the databases holding the following types of information:
Details of DB/DM development activities are given in Chapter 4 of this document.
This project groups all activities related to the definition of the Grid services that we need for the operation of our Computing Model, as well as the development and deployment of our production system and related tools. It includes the following activities:
Details of Grid tools and services development activities are given in Chapter 5 of this document.
This project groups all activities related to the efficient operation of the ATLAS computing system. It includes in particular the following activities:
Details of the activities related to computing operations, as well as of Data Challenges, are given in Chapter 6 of this document.
This project covers all administrative and managerial aspects relative to ATLAS computing operations. In particular, it consists of the following work packages:
The software environment of the TDAQ High-Level Trigger and the offline system are tightly coupled, as they share the framework, the data store in memory and the HLT algorithmic code. The performance requirements of the HLT are clearly stronger than those of the offline users, therefore a close cooperation in the design of the common components is necessary. For this reason, an HLT liaison person is present in the SPMB; the Architecture Team also includes TDAQ and HLT people.
Conditions and configuration data have to be exchanged between the online and offline systems. In order to ensure coherent developments, the DB/DM project oversees online applications of databases and includes in its steering group the persons responsible for their development.
The Computing Model Working Group includes a TDAQ liaison person whose task is to make sure that there is a consistent model, and implementation, for the flow of event and non-event data from the online to the offline system.
At a higher level, a TDAQ liaison person is a member of the CMB, and the Computing Coordinator, Software Project Leader and DB/DM Project Leaders are members of the TDAQ Steering Group. As outlined above, the COB also acts as a communication channel between the projects and with ATLAS management.
The aim of all software and computing development and operation activities is to enable all ATLAS physicists to analyse the data. It is therefore extremely important that there be a continuous flow of communication between the physics and computing communities, in one direction to provide requirements and feedback, and in the other direction to provide tools, information on what can be done and how, and user support.
At the highest level, the Computing Coordinator is a member of Physics Coordination, and likewise the Physics Coordinator is a member of the CMB; both are members of the COB. The Physics Software Validation Coordinator, appointed by the Physics Coordinator, is a member of the SPMB.
The Combined Performance Working Groups (e-gamma, jets, tau/etmiss, muons, flavour tagging) meet during Software & Computing Workshops in order to increase the contacts between people interested in physics performance and software developers. The ESRAT (Event Selection, Reconstruction & Analysis Tools) group (see Section 3.9 ) provides a discussion forum on detector and combined reconstruction algorithms and performance that involves HLT and offline developers as well as physics analysis users.
In addition, software and computing issues, as seen by end-users, are always treated among the topics of the ATLAS Physics Workshops.
A Commissioning Coordination structure was set up in ATLAS at the beginning of 2004. It includes two Offline Commissioning Coordinators, who are also members of the CMB. Their task is to collect the requirements for offline software support by the detector groups, plan the necessary development activities and oversee their implementation. Liaisons towards the Commissioning organization have been appointed by all offline software detector groups. More details can be found in Section 3.12 .
There are interactions at all levels between ATLAS and the LCG project. The spokesperson is a member of the LCG Project Oversight Board (POB). The Computing Coordinator is a member of the LCG Project Execution Board (PEB). The Software Project Leader is a member of the LCG Applications Area Architects Forum (AA). ATLAS is also represented by the Computing Coordinator, the Computing Resources Manager and the Computing Operations Manager in the LCG Grid Deployment Board (GDB). Four ATLAS collaborators are members of the LCG Grid Applications Group (GAG). ATLAS also takes an active part in the SC2 (the LCG project monitoring body) and the LHC4-Computing group (the regular discussion group that includes the ATLAS spokesperson, the deputy in charge of computing, the computing coordinator, the ICB chair and the members of the other LHC experiments holding equivalent positions).
In order to ensure efficient cross-communication between ATLAS representatives in all these bodies, the "ATLAS-LCG Management Team", grouping all these people, meets weekly to exchange relevant information.
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