1. CMS High Level Trigger Configuration Management
Computing in High Energy Physics, Victoria BC
September 3, 2007
Emilio Meschi – CERN PH/CMD

2. CMS Data Acquisition System
~108 electronics channels, 40 MHz crossing rate
Two trigger levels:
L1 (hardware)  100 kHz max accept rate
Event building at full L1 rate
High Level Trigger (software)  200 Hz
Event Filter
Filter Farm O(1000) systems execute HLT algos
Data logging system 1GB/s, 250TB capacity
Mention or be prepared to discuss L1 configuration
Mention HLT “exercise” benchmark
HLT decision
~40 ms/event
Events fully built in
worker node memory
EM - CMS HLT Configuration Management - CHEP07

3. HLT: Design Considerations
Online and Offline reconstruction/selection: one reconstruction framework
Maximum flexibility
Wider community of developers
Faster migration of algorithms developed offline
HLT steering
Instances of algorithms and filters provide selection of particular category of events
arranged and executed in strict sequence (trigger path)
Each path executed up to first negative filter decision or to the end
Every path executed for every event (guarantees traceability)
EM - CMS HLT Configuration Management - CHEP07

4. EM - CMS HLT Configuration Management - CHEP07
HLT and Offline
CMS reconstruction framework
Modular architecture, enforcing component interfaces
Input, reconstruction, filtering, access to calibrations etc.
Modules loaded and configured at initialization using plug-in system
Object representation of configuration completely defines instances of algorithms, their parameters and the sequence of execution
Different grammars map object model to provide flexible file-based configuration of offline jobs
Offline HLT development and benchmarking
Algorithm development and MC physics benchmarking
Integration of trigger paths
Integration of initial table
CPU performance and first optimization
See talk by L.Apanasevich, this session
EM - CMS HLT Configuration Management - CHEP07

5. EM - CMS HLT Configuration Management - CHEP07
Offline ‘HLT’
Plugin
declaration
Configuration
subdocument
Module
parametrization
Offline job
Trigger Table
Output
EM - CMS HLT Configuration Management - CHEP07

6. EM - CMS HLT Configuration Management - CHEP07
HLT and Online Systems
Online framework (XDAQ)
Provides plug-in mechanism: ‘executive’ program loads online components
Dispatches control message
Provides data transport in a distributed environment
Integration: enable DAQ process to load offline modules and define special interfaces for input/output, control, and monitoring
Run Control
Deploys online applications in XDAQ distributed environment
Configures and controls distributed system using tree of state machines (Function Managers)
presentation by A. Oh in this track (Thursday)
HLT Configuration and control: HLT Function Manager (HLTS)
At configuration, loads trigger table upon instruction of Run Control
Retrieves actual configuration ‘document’ and distributes to Filter Farm processes
EM - CMS HLT Configuration Management - CHEP07

7. HLT Configuration Management
File based system issues
Concurrent versioning of multiple tables technically difficult
Hard to maintain in the long term:
evolution of the grammar and algorithms
Potential consistency problems in distributed environment
CLOBs only partially address 1 And 2
Configuration Management: requirements
Abstract DB model of framework components and of trigger table
Little or no dependence of configuration grammar
Populate table in DB based on specific software version
automatic migration to different version
Unique table identification in the system for online use
Automatic conversion to specific grammar
Graphical user interface
Additionally
Support offline development/validation workflow of HLT algorithms
EM - CMS HLT Configuration Management - CHEP07

8. Configuration Management System
DATABASE
Describe relation between services,
paths, modules and parameter
Enable creation of table based on templates in the db. Enforce basic rules Provide table traversal
TEMPLATES
HLT
CONFIGURATIONS
Discover all relevant sw components and store templates in db for given sw release
GUI
DB INTERFACE
CONVERTER
PARSER
RUN CONTROL
Provide retrieval and conversion of table to different formats
CONVERTER
SOURCE
CODE
FILTER FARM
EM - CMS HLT Configuration Management - CHEP07

9. EM - CMS HLT Configuration Management - CHEP07
Components I
Database: relational schema
Store algorithms and parameter defaults in templates from parsing of sw release
Store configuration as references to paths, paths as sequences of module instances
Module instances as references to respective template plus set of non-default parameters
Oracle and MySQL compatible
Parser: python scripts
Traverse source tree of reconstruction software release
Discover all components and their parameters, plus default values
Traverses 1.5 MSLOC (CMS reconstruction) in ~1 min
Explain need to parse code
Give example
EM - CMS HLT Configuration Management - CHEP07

10. EM - CMS HLT Configuration Management - CHEP07
Components II
Graphical User Interface: java application
Load template definitions from DB
Configuration displayed as tree
Context menus filled from template info to populate configuration
Enforces basic configuration rules and consistency
Converter: java API
Accesses database to retrieve configuration and translate into valid grammar or other representation
E.g. html for easy navigation of table (for physicists, or the curious)
API used by Run Control to configure filter farm
Web service for global access to HLT configurations in use
EM - CMS HLT Configuration Management - CHEP07

11. GUI Screenshot Configuration Drag and drop, db migration properties
sw version update
quick document generation
Module details
Configuration
tree
EM - CMS HLT Configuration Management - CHEP07

12. HLT Configuration Workflow
EM - CMS HLT Configuration Management - CHEP07

13. EM - CMS HLT Configuration Management - CHEP07
Summary
HLT Configuration Management System designed to
Support online validation and operation of HLT configurations and their long term maintenance
Help offline development and validation of HLT algorithms and tables
Currently under commissioning as part of the HLT validation effort
Complex, realistic trigger table (~100 paths)
From HLT “exercise” benchmark mentioned previously
Simulated input (raw data from MC events)
Benchmark of performance and stability of algorithms
Also in use for detector commissioning
No physics selection but realistic environment
Configuration of basic reconstruction (reformatting, data consistency, local reconstruction) and monitoring
Test of online workflow, scalability
EM - CMS HLT Configuration Management - CHEP07