The IBM SP-1 is a new parallel computer designed to make the best use of IBM's powerful RISC technology combined with a high-speed switch. Special features of this SP-1 are:
The peak performance of each node is 125 Mflops (1674-bit floating point add and 1 floating point multiply in each clock cycle). In practice, each node can achieve between 15 and 70 Mflops on Fortran code. Higher performance can be reached by using BLACS or ESSL routines.
Each SP-1 node is running a full Unix; most of the usual Unix tools are available. Users may log directly into any SP-1 node using telnet, rlogin, or rsh. The software of the ANL SP-1 includes multiple parallel programming environments, IBM's ESSL library, and performance debugging tools.
Communication between nodes can be carried out by many ways which one can choose. Most users will not use these directly; rather they will use one of the portable programming libraries. However, as the programming libraries use these transport layers to actually accomplish the communication, it is important to understand them so that the proper transport layer can be chosen.
The available transport layers are Ethernet, IP, Switch/IP, and EUI-H.Only the first two support multiple parallel jobs on the same node. Both versions of EUI can only run one process per node. In addition, EUI-H is incompatible with EUI and Switch/IP on the same nodes (though the SP-1 can be configured so that EUI-H runs on some nodes and EUI and Switch/IP run on the others; this is a common daytime configuration at ANL.
Using the Ethernet transport layer with all nodes connected by
Ethernet, the SP-1
looks just like a collection of workstations. This method does suffer from
the same drawbacks as any Ethernet-connected system: high latency (about 1
sec) and low bandwidth (1 MByte/sec is shared among all processors). The IP
transport layer provides enhanced performance to code written using Unix
sockets for interprocessor communication.
EUI is IBM's message-passing interface to the high-performance switch.
There are two versions:
one that works with the Parallel Operating Environment (POE) and one that
does not. EUI refers to
the POE version. POE supports a parallel symbolic debugger (xpdbx) and a
performance
visualization tool (vt). However, its performance is inferior to EUI-H
(latency is about 405 sec). In
addition, at most 64 nodes are available to EUI. EUI-H is an experimental,
low-overhead implementation of the EUI interface.
It does not support
either xpdbx or vt. It is difficult to provide standard input to EUI-H
programs.
Also, it is not possible to produce gprof-style profiling
information from EUI-H
programs. All 128 nodes may be accessed using EUI-H when the machine is
configured for that.
Note that this
version of EUI-H is the
version of IBM Research; it contains only the Fortran bindings for EUI.
IP and EUI applications may share the switch; multiple IP applications may
share
both nodes and
the switch. IP and EUI run under the ``Parallel Operating Environment,'' or
POE.
POE includes a
number of tools, such as a parallel debugger and ParaGraph-like
visualization tool
(vt). These two transport layers share a common interface to the switch
known as lightspeed.
Parallel Libraries: