CHEP 06

OHP: An Online Histogram Presenter for the ATLAS experiment

Feb 16, 2006, 2:00 PM

18m

AG 76 (Tata Institute of Fundamental Research)

oral presentation Event processing applications Event Processing Applications

Speaker

Dr Andrea Dotti (Università and INFN Pisa)

Description

ATLAS is one of the four experiments under construction along the Large Hadron Collider ring at CERN. During the last few years much effort has gone in carrying out test beam sessions that allowed to assess the performance of ATLAS sub-detectors. During the data taking we have started the development of an histogram display application designed to satisfy the needs of all ATLAS sub-detectors groups. The requirements that have driven the design of this application are: possibility to display histograms produced by many different producers, possibility to use it both as a configurable presenter and as a browser, possibility to manage user actions on histograms, possibility to allow comparison with reference histograms, high integration with the ATLAS DAQ software, minimization of the network traffic between presenter and producers. A first prototype of this application has been implemented and extensively used at the 2004 ATLAS Combined Test Beam and, from this experience, an upgraded application has been developed to be used in the ATLAS commissioning in 2007. The presentation will describe the program architecture and its interactions with the ATLAS DAQ software, including the first results obtained from the performance tests.

Summary

One component of the ATLAS Data Acquisition and Trigger System (TDAQ) is the Online
Histogram Service (OHS) which can be used as histogram transient store. OHP access
histograms, generate by any producer, through this service. To minimize the network
traffic, the histogram are accessed through a mixed push/pull approach. A
notification of the availability of an updated histogram is automatically sent to OHP
as soon as it is published in the OHS. OHP, if the histogram must be displayed in the
on-focus window, gets the histogram object from OHS.
The histogram presenter, based on the Qt libraries and on ROOT framework is at the
same time a browser and a presenter. The first functionality is implemented building
at start time a graphic directory structure that allows to access any histogram
stored in the OHS. The directory structure is built according to the histogram names
which are defined following a strict convention. The second functionality, the
presenter, is implemented building a set of windows where a subset of histograms are
displayed. Both the histograms to be shown and their organization in windows are
defined through a configuration file. In this mode it is also possible to display
reference histograms.
The histograms are managed in ROOT format thus all the operations allowed in ROOT
(zoom, fitting,...) are also allowed in the presenter windows.
In addition to that the presenter is able to send back to the producers commands like
rebin and reset of histograms.
A sub-system for plug-ins has been also developed allowing for user code to be
executed inside the presenter. This system allows the user to develop a library that
can interact with the presenter, for example drawing in the windows graphical
objects, or to execute quality-check algorithms on the histograms.

The presentation will include a description of the program architecture and of its
interaction with the ATLAS TDAQ software, including the first results obtained from
the performance tests.
Future possible upgrades will also be discussed.

Presentation materials

Paper

Paper

Paper

Slides

slides