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Institute for Computing Systems Architecture

Computer Architecture Simulation & Visualisation


The QCD Computer Simulation Project

Overview | Contributors | QCD | UKQCD | Publications | HASE Models

Project Overview

The aims of the QCD Computer Simulation project were: Parameterised hardware-software co-simulation models of the QCDOC architecture were created using HASE and experiments were conducted to investigate its performance. At the same time, the capabilities of HASE were extended in response to the demands placed on it by the requirements of these models.

An extension to the project has been to introduce a metamodelling scheme which allows for efficient generation of simulation models with alternate system configurations. This has allowed us to model and evaluate the IBM Bluegene/L architecture.

The QCD Computer Simulation project was supported by EPSRC (Grant GR/R/27129) from May 2001 to April 2004. Further details can be found in the EPSRC Final Report.



Quantum Chromodynamics

Quantum Chromodynamics (QCD) describes theoretically the strong interactions between quarks and gluons. One of the essential features of QCD is that these elementary particles are always bound together, confined inside mesons and baryons, collectively called hadrons. This provides a challenge in relating theoretical and practical results, since the Standard Model of particle physics describes the interactions of the quarks and gluons, not of the experimentally observed hadrons.

To relate the experimental observations to the predictions from the Standard Model thus needs detailed evaluation of the hadronic structure, relating the quark constituents to the observed hadronic properties in a precise way. The only theoretical method to achieve this, with full control of all sources of error, is via large-scale numerical simulation: lattice QCD.

The UK QCD Collaboration

The UKQCD collaboration is one of the leading lattice QCD projects in the world, having pioneered many successful applications to particle physics phenomenology. It has recently been awarded JIF funding to build the fastest computer in the world for simulating strong interactions.

The UKQCD machine will be based on the Columbia QCDOC architecture. QCDOC is a natural evolution of the massively parallel QCDSP machine which won the 1998 IEEE Gordon Bell prize for the best price/performance high-end computer. The individual processing nodes in QCDOC will be Power PC-based and interconnected in a 4-dimension mesh with the topology of a torus. Each node in QDOC will be a single applications specific integrated circuit (ASIC) containing a 500 MHz 440 PowerPC processor core with a 1 Gflops, 64-bit floating point unit and 4 MBytes of on-chip memory together with a Direct Memory Access (DMA) unit for moving data between on-chip and external memory. It will also contains circuitry to support internode communication and an Ethernet controller for a boot-diagnostic-I/O network.

Each processor will be capable of sending and receiving data from each of its eight nearest neighbors in four dimensions at a rate of 500 Mbit/sec. This will provide a total off-node bandwidth of 8 Gbit/sec. Each of these 16 communication channels will have its own DMA capability allowing autonomous reads/writes from either on-chip or external memory. As in the QCDSP machines, an efficient and low-latency global sum, global max and broadcast capability will be incorporated into the serial communication.

QCD Papers




HASE Models

HASE models of QCDOC were developed at two different levels of abstraction. The low-level model, which can simulate up to 16 processing nodes, captures the microarchitectural details of the system, including the processor, the on-chip cache hierarchy, the system bus, the communication unit, etc. This model was used to study the performance characteristics of a single node and nearest neighbour communications when executing QCD code.

In the high-level model, which can simulate up to 12K processing nodes, the nodes simply act as sources of communication events, with the intervals between events being based on data taken from the low-level abstraction model. This model was used to study the performance characteristics of the custom communication protocol and different ways of implementing the QCD global sum mechanism.

More details of the models can be found at HASE QCDOC Models (These pages are under construction).


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HASE Project
Institute for Computing Systems Architecture, School of Informatics, University of Edinburgh
Last change 20/07/2004

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