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\chapter{NPAC Meta Computer}

The NPAC meta-computer is equipped with computational resources with 
a variety of the most recent HPCC technologies. Although the
structure of installed facilities is not geared toward high volume production needs, it offers
considerable computing power. The real asset of the meta-computer, however, is 
diversity of its resources.
Collectively, as a whole meta-machine, or separately, with partial configuration, it
is able to support almost every HPCC application and
provide testbeds for a multitude of computationally intensive projects, including
most of the case study projects described in this thesis.

\begin{figure}
\centerline{\epsfxsize=400pt \epsfbox[70 60 550 730]{appendix/NPACfacility.ps}}
%%BoundingBox: 53 40 560 753
\caption{NPAC meta-computer - processing nodes}
\label{npac-machine}
\end{figure}

As shown in Figure \ref{npac-machine}, the processing nodes of this meta 
computer can be broadly divided into three categories: 
\begin{enumerate}
\item Parallel supercomputer 
\item Clusters of high-performance workstations 
\item Desktop workstations for program development and data visualization 
\end{enumerate}

\section{Parallel Machines}

The parallel machines currently installed include a CM5, an iPSC 860, two DECmpp
machines, an SP2, and an nCUBE 2. They represent the major current architectural trends for MPP
platforms. The configuration and utilization data for these machines are as follows: 

\begin{enumerate}
\item 
The CM5 is a 32-node model from Thinking Machines Corporation. Every node has 32MB of
memory and, besides a Sparc-1 scalar CPU, four vector units. The nodes are connected by
TMC proprietary network with quad-tree topology. The peak computational power of our
CM5 is estimated at 3 GFLOPS. 

\item
The iPSC 860 from Intel is a 16-node model with 256 MB of RAM and with hypercube
interconnect topology. It features a small-scale concurrent file system. 

\item
Two DECmpp machines are large systems in their category. Both are 100 models with 8K and
     16K processors, respectively. The DECmpp machines are SIMD computers featuring a large number
     of relatively unsophisticated processors operating in data-parallel fashion. The DECmpp
     machines are equipped with a high-speed I/O channel and can communicate over the HiPPI interface.
     Their architecture makes them suitable for regular problems. The aggregate peak computing
     power of the DECmpp ensemble is 2.5 GFLOPS. They are  
     ideally suited for image processing and data-compression
     applications. DECmpp platforms offer relatively sophisticated and user-friendly software
     support. 
\item
The SP2 machine is the newest HPCC product of the IBM corporation. Unlike the other machines
     installed in NPAC, the SP2 consists of a relatively low number (8 thin/4 wide) of very powerful
     nodes. The nodal processor of the SP2 is an IBM RISC/6000 processor running at 62.5 MHz,
     one of the most powerful processors available. Internal connectivity of the SP2 is provided by
     both the Ethernet network and by the high-performance switch with crossbar topology (full
     connectivity). The parallel processing environment of the SP2 supports both distributed (loosely
     coupled) and parallel (tightly coupled) programming paradigms. Due to the binary
     compatibility, the SP2 can be easily integrated with IBM workstation clusters. It is a very flexible,
     general purpose platform with considerable computing power and is able to support a variety of
     HPDC applications. 
\item
The nCUBE 2 installed is a 64-node, 2 GB RAM machine with MIMD hypercube
     architecture. The salient feature of the NPAC machine is its scalable parallel I/O subsystem. The
     subsystem, working in parallel with the computational processor array, consists of 32 nodes that
     form its own hypercube, with an SCSI controller and a disk array connected to every node.
     The current configuration supports 96 disks with total storage capacity of nearly 0.2 TB. The I/O
     subsystem also supports networking processors and controllers. It represents a state-of-the-art
     scalable I/O system, probably the most advanced in the industry.  It 
     possesses the capability to support large, high-performance data-processing applications.

\end{enumerate}

\section{Workstation Clusters}

The relatively distributed computing elements include two clusters of high-performance workstations:
an IBM R/6000 cluster and a DEC Alpha cluster. An IBM heterogeneous cluster consists of eight workstations
(models 550 and 340). Four of the workstations are connected via a high bandwidth, low-latency Allnode
switch. Both SP2 and cluster nodes will run the same Parallel Programming
Environment software and Load Leveler scheduler. This integration will almost double the CPU
power of SP2, presenting users with a single-system view of both the SP2 and the cluster. 

The DEC Alpha cluster consists of eight Alpha model 400 compute servers. These workstations represent
the newest and most advanced development in workstation technology. The cluster is supported by
a high-performance networking backbone consisting of dedicated, switched FDDI segments. This
solution provides full FDDI bandwidth and low-latency switching to every workstation in
the cluster. The model implemented in NPAC exemplifies Digital's latest approach to distributed
computing. Together with the DECmpp machines, the cluster will be used to demonstrate the viability of
using a highly heterogeneous computing environment to solve computational problems with very
irregular structures. 

Both clusters of workstations provide meta applications with a unique distributed processing environment.
The clusters support a growing class of computational problems that are both irregular (hence difficult
to parallelize) and non-vectorizable (hence running inefficiently on vector supercomputers). 

\section{Desktop Workstations}

While most of the highly heterogeneous network of desktop workstations are
used by NPAC researchers for everyday operation,
including program development, document processing, multimedia, and scientific visualization, some of
them are also used as part of the meta-machine in a variety of applications.
The network includes a variety of workstations from vendors that include SGI, DEC, and Sun. Scientific
visualization capability is provided by few high-end SGI workstations and by the IBM graphic
workstations integrated with the IBM SP2/workstations cluster. 

Overall, the meta-computer represents a state-of-the-art HPCC center providing its
partners with access to the newest technology. The unique capabilities of the NPAC computational
infrastructure offer a number of benefits that assist NPAC users in developing novel HPCC
applications. These capabilities include:
\begin{enumerate}
     
\item A number of different parallel architectures can be gathered in one place. This allows for extensive
     experiments and for identification of the most suitable architecture for a particular project. 
     
\item In addition to diverse parallel systems, loosely coupled distributed systems are also supported,
     thus extending the overall meta-machine capability and allowing for integration of the technologies
     required to solve extremely irregular problems. 
     
\item The integration capability is supported by an efficient networking backbone. This capability
     will soon be extended to applications running on geographically remote computers by
     interfacing NPAC's internal LAN to the NYNet high-speed network. NYNet will also support
     applications that require very high bandwidth for data exchange between supercomputers,
     including support for multimedia and telepresence applications in diverse fields. 
     
\item Both traditional ``number crunching'' and data processing platforms are available. This makes it possible
     to test distributed applications that have both intensive data processing and computational
     components. Both database applications (parallel database server) and I/O intensive applications
     (parallel I/O subsystems) are supported. 
     
\item The NPAC heterogeneous environment makes considerable computing power available to NPAC
     partners and users of its facilities. 
\end{enumerate}

\section{Networking}

\begin{figure}
\centerline{\epsfxsize=350pt \epsfbox[70 30 550 770]{appendix/NPACnet.ps}}
%%BoundingBox: 11 3 601 790
\caption{NPAC meta-computer - interconnections (networking)}
\label{npac-network}
\end{figure}

Internally and locally, the processing elements of the meta machine system
are inter-connected by multi-vendor, multi-bandwidth, and heterogeneous local
networks (see Figure \ref{npac-network}). The main networking FDDI backbone 
is built around the Gigaswitch (Digital), a high-speed, low-latency 
multiswitch with interfaces to both FDDI and ATM networking technology. A section of the
Gigaswitch supports the networking of the Alpha cluster. Other sections of the same device support
access to NPAC's file servers and provide connection to the router supporting Ethernet connectivity.
A second networking backbone based on the HiPPI technology 
backbone interconnects
the two DECmpp machines and other machines for a single point-to-point connection and
high-bandwidth communication. 

Many of the modern applications require a bandwidth much higher
than what is currently available. To achieve this goal, a regional alliance has been formed to
implement the ATM-based high-speed network. The network, NYNet, is being supported by NYNEX,
one of the baby-Bell companies, and its participants include Cornell University, Syracuse University,
Rome Laboratory, and the Museum of Science and Technology in Syracuse in upstate New York, and
Brookhaven National Laboratory, SUNY Stonybrook, Columbia University, Brooklyn Polytechnique,
and NYNEX Science and Technology Center in downstate New York. The network offers OC-12 capability. 
NYNet will offer high-speed access to most of the NPAC resources and will allow for
extensive experiments in wide-area distributed computing involving resources of the computing
centers in all participating institutions. 

The FDDI, ATM, and HiPPI networking technologies must be integrated to ensure internal
interoperability and remote access to NPAC resources. This goal is realized by the
installation of a Challenge, the powerful Silicon Graphics network server. This unit provides
a central-point, high-performance gateway between different networking backbones installed in NPAC
and will serve the purpose of a HiPPI switch, a HiPPI--FDDI--ATM gateway, and a direct
interface to the second OC-3/OC-12 line of NYNet. This can provide support for geographically
distributed applications that require gigabit bandwidth technology. 

