1. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 1 New Test Results for the ALICE High Level Trigger

2. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 2 ALICE High Level Trigger Overview ● ALICE: LHC heavy-ion experiment ● Up to 15,000 particles per event ● HLT input data rate: Up to 25 GB/s ● HLT output to storage: 1.2 GB/s ● Online reconstruction in several steps ● ADC values → 3D coordinates → track segments → tracks ● No latency requirements ● Large commodity PC cluster ● Hierarchy levels (HL) to match physical detector layout 1, 2, 123, 255, 100, 30, 5, 1, 4, 3, 2, 3, 4, 5, 3, 4, 60, 130, 30, 5,..........

3. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 3 ALICE High Level Trigger Overview Software framework to transport data through cluster ● Requirements: Flexible, efficient, fault-tolerant ● Components that communicate via defined interface ● Interface does not copy large event data – Only descriptors – Lowers CPU load for data transport ● Components to define flow of data in cluster ● Component templates for application specific functionality ● Components can be plugged together to create systems w. arbitrary functionality ● Data-driven architecture ● Components receive data from other components ● Process received data ● Forward output data to next component Input Processing Output Input Processing Output

4. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 4 Interface Test Results Benchmarks of Publisher/Subscriber Component Interface ● Only interface benchmarked ● No shared memory access ● Pentium 4 family influenced by L1 cache size (only 8kB) ● Maximum rate: >110 kHz (Dual Opteron) ● CPU overhead f. full event round-trip: <18 μs

5. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 5 HLT in TPC Sector Beamtest Goals of HLT participation in TPC testbeam – Test of DAQ-HLT interface – Gain real world operation experience PCI Card DAQ PC 1 PCI Card DAQ PC 2 Fast Ethernet DAQ PC 3 3x 250 GB disk Optical Link Optical Link Optical Link Detector Prototype Optical Link Mass Storage 1 MB/s HLT PC 1 PCI Card (RORC) HLT PC 3 HLT PC 2 PCI Card (RORC) PCI Card (HLT-Out) Gigabit Ethernet 10 MB/s

6. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 6 TPC Sector Beamtest HLT Software ● EventRateSubscriber measures event receiving rate ● StorageWriter writes data to local disc Optical Link HLT PC 1 RORC Publisher Subscriber BridgeHead HLT PC 3 Publisher BridgeHead Publisher BridgeHead Event Merger Storage Writer HLT-Out Subscriber EventRate Subscriber HDD HLT PC 2 RORC Publisher Subscriber BridgeHead Storage Writer HDD Optical Link

7. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 7 HLT in Readout of TRD Beamtest ● No optical link interface for TRD prototype ● Use HLT output card for DAQ connection ● Adapt HLT input component to TRD prototype interface readout PCI card (ACEX card) ● TRDFormatter checks data, adds header f. optical link ● Optional local output via StorageWriter Detector Prototype HLT PC PCI Card LVDS Link ACEX Publisher HLT-Out Monitoring PCI Card DAQ PC HDD TRD Formatter Optical Link Storage Writer

8. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 8 HLT TaskManager Control System ● System to control large number of components in final HLT ● Fault-tolerant ● No single-points-of-failure ● Hierarchical, master-slave ● Flexible configuration ● XML and Python based ● Interface libraries to communicate with controlled programs Core Configurati on Engine XML Configurat ion File Interfac e Library Controlled Programs Program State & Action Engine Embedded Python Interpreter TaskManager Program Interface Engine

9. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 9 HLT Control System Master TaskMana ger Slave TaskMana ger 1 Slave TaskMana ger 2 RORC Publish er Storage Writer Subscribe r BridgeHea d Publisher Bridge Head Publisher Bridge Head HLT-Out Subscrib er Event- Rate Subscrib er – Status & Command flow is black HLT PC 2 HLT PC 3 Event Merger Slave TaskMana ger 0 RORC Publish er Storage Writer HLT PC 1 Subscribe r BridgeHea d – Data flow is yellow System used to control HLT in TPC Beamtest

10. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 10 Cape Town Heidelberg Bergen Dubna Tromsø Global Processing Test ● Proof-of-concept global online grid system ● High Level Trigger system distributed globally ● Not just distributed on one cluster ● Distributed on five clusters ● Bergen & Tromsø,Norway ; Dubna, Russia ; Heidelberg, Germany ; Cape Town, South Africa ● Test run for more than 15h ● Framework designed for operation in cluster also works globally

11. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 11 Global Processing Test Setup & procesing steps used Bergen,Norwa y Simulated TPC Clusterfinding 3 PCs Heidelberg, Germany Simulated TPC Tracking 2 PCs Tromsø,Norw ay Simulated TPC Clusterfinding 2 PCs Dubna, Russia Simulated TPC Clusterfinding 1 PC Capetown, South Africa Simulated DiMuon Tracking + Global Event Merging 7 PCs

12. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 – HK 41.2 12 Conclusion ● ALICE High Level Trigger Data Transport Software has reached mature state ● Performance on current CPUs enough for use in HLT ● Stable ● Can also operate in globally distributed online grid-like system ● Used successfully in two beamtest – TPC beamtest for interface tests – TRD beamtest used for production data readout ● Current/future development concentrates on higher layers, e.g. control system