High Performance Computing and Communications Glossary 2.1

A significant part of the material of this glossary was adapted from material originally written by Gregory V. Wilson which appeared as "A Glossary of Parallel Computing Terminology" (IEEE Parallel & Distributed Technology, February 1993), and is being re-printed in the same author's "Practical Parallel Programming" (MIT Press, 1995). Several people have contributed additions to this glossary, especially Jack Dongarra, Geoffrey Fox and many of my colleagues at Edinburgh and Syracuse.

Original version is from NPAC at <URL:http://nhse.npac.syr.edu/hpccgloss/>

Original author: Ken Hawick, khawick@cs.adelaide.edu.au

See also the index of all letters and the full list of entries (very large)

Sections: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


halo (n.) The region around a point in a mesh, whose values are used when updating the value of the central point. In a cellular automata, the halo comprises those neighbouring cells whose values are used by the automaton's update rule.

Hamiltonian(n.) A closed path through a graph which passes through each node in the graph exactly once.

Hawick (n.) a Scots word meaning a "town surrounded by a hedge"; also an actual town on the border between Scotland and England; also my surname. This is not relevant to HPCC except that this is a usful way of ensuring my email address (hawick@npac.syr.edu) does not get lost from this file so you can always seek out the latest version of this glossary.

HDB3 (n.) High density bipolar three, a line interface standard for E1 which is similar to B8ZS, which eliminates data streams with 8 or more consecutive zeros. Allows for 64Kbps clear channel capacity and still assure a minimum ones density required by E1 lines.

HDLC (n.) high level link control is an ISO link level protocol standard. CCITT uses HDLC for its link access protocol with X.25 networks. HDLC was used in the ARPANET to transfer frames between hosts and packet switched networks.

height (n.) in graph theory, height is the length of the longest path from the root of a tree to one of its leaves.

heterogeneous(adj.) Containing components of more than one kind. A heterogeneous architecture may be one in which some components are processors, and others memories, or it may be one that uses different types of processor together. See also distributed computer, homogeneous.

high-order interleaving (n.) memory interleaving strategy based on high-order bits of an address.

HiPPI (n.) High performance parallel interface; a point to point 100 MByte/sec interface standard used for networking components of high performance multicomputers together.

hit ratio (n.) the ratio of the number of times data requested from a cache is found (or hit) to the number of times it is not found (or missed).

homogeneous(adj.) Made up of identical components. A homogeneous architecture is one in which each element is of the same type; processor arrays and multicomputers are usually homogeneous. See also heterogeneous.

hop (n.) A network connection between two distant nodes.

horizontal processing (n.) act of processing a two dimensional array row by row.

Horn clause (n.) a clause that contains at most one conclusion.

hot-spot contention (n.) an interference phenomenon observed in multiprocessors caused by memory access statistics being slightly skewed from a uniform distribution to favour a specific memory module.

HPCC (n.) an acronymn for High Performance Computing and Communications, which is the field of information addressed by this glossary. A USA National Coordination Office for HPCC also exists, and other information on HPCC can be found from the Northeast Parallel Architectures Center, the Center for Research in Parallel Computing the National Software Exchange or the Edinburgh Parallel Computing Centre depending upon your geography.

hypercube (n.) A topology of which each node is the vertex of a d-Dimensional cube. In a binary hypercube, each node is connected to n others, and its co-ordinates are one of the 2^n different n-bit sequences of binary digits. Most early American multicomputers used hypercubic topologies, and so the term hypercube is sometimes used as a synonym for multicomputers. See also butterfly, e-cube routing, shuffle exchange network.