New Test Results for the ALICE High Level Trigger. Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK 41.

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

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 1, 2, 123, 255, 100, 30, 5, 1, 4, 3, 2, 3, 4, 5, 3, 4, 60, 130, 30, 5, 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 HL2 HL1 HL0 HL0-HL2 Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK HL3

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 Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

4 Interface Test Results Benchmarks of / 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 Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

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

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

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) HLT PC Storage Writer HDD LVDS Link ACEX TRD Formatter HLT-Out DAQ PC Detector Prototype Monitoring TRDFormatter checks data, adds header f. optical link Optional local output via StorageWriter Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

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 Configuration File Configuration Engine Embedded Python Interpreter Program State & Action Engine XML and Python based Interface libraries to communicate with controlled programs Core TaskManager Program Interface Engine Interface Library Controlled Programs Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

9 HLT Control System System used to control HLT in TPC Beamtest Status & Command flow is black HLT PC 3 Master TaskManager Data flow is yellow HLT PC 1 Slave TaskManager 0 Slave TaskManager 1 HLT PC 2 Slave TaskManager 2 RORC Bridge Head Bridge Head RORC Storage Writer Storage Writer BridgeHead HLT-Out Event Merger Event-Rate BridgeHead Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

10 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 Bergen Heidelberg Tromsø Dubna Framework designed for operation in cluster also works globally Cape Town Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK

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

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 Timm M. Steinbeck - Kirchhoff Institute of Physics - University Heidelberg - DPG 2005 HK