parallel
    adj 1: being everywhere equidistant and not intersecting;
           "parallel lines never converge"; "concentric circles are
           parallel"; "dancers in two parallel rows" [ant:
           oblique, perpendicular]
    2: of or relating to the simultaneous performance of multiple
       operations; "parallel processing"
    n 1: something having the property of being analogous to
         something else [syn: analogue, analog, parallel]
    2: an imaginary line around the Earth parallel to the equator
       [syn: latitude, line of latitude, parallel of latitude,
       parallel]
    3: (mathematics) one of a set of parallel geometric figures
       (parallel lines or planes); "parallels never meet"
    v 1: be parallel to; "Their roles are paralleled by ours"
    2: make or place parallel to something; "They paralleled the
       ditch to the highway" [syn: parallel, collimate]
    3: duplicate or match; "The polished surface twinned his face
       and chest in reverse" [syn: twin, duplicate, parallel]

Parallel \Par"al*lel\, a. [F. parall[`e]le, L. parallelus, fr.
   Gr. ?; para` beside + ? of one another, fr. ? other, akin to
   L. alius. See Alien.]
   1. (Geom.) Extended in the same direction, and in all parts
      equally distant; as, parallel lines; parallel planes.
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            Revolutions . . . parallel to the equinoctial.
                                                  --Hakluyt.
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   Note: Curved lines or curved planes are said to be parallel
         when they are in all parts equally distant.
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   2. Having the same direction or tendency; running side by
      side; being in accordance (with); tending to the same
      result; -- used with to and with.
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            When honor runs parallel with the laws of God and
            our country, it can not be too much cherished.
                                                  --Addison.
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   3. Continuing a resemblance through many particulars;
      applicable in all essential parts; like; similar; as, a
      parallel case; a parallel passage. --Addison.
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   Parallel bar.
      (a) (Steam Eng.) A rod in a parallel motion which is
          parallel with the working beam.
      (b) One of a pair of bars raised about five feet above the
          floor or ground, and parallel to each other, -- used
          for gymnastic exercises.

   Parallel circles of a sphere, those circles of the sphere
      whose planes are parallel to each other.

   Parallel columns, or Parallels (Printing), two or more
      passages of reading matter printed side by side, for the
      purpose of emphasizing the similarity or discrepancy
      between them.

   Parallel forces (Mech.), forces which act in directions
      parallel to each other.

   Parallel motion.
      (a) (Mach.) A jointed system of links, rods, or bars, by
          which the motion of a reciprocating piece, as a piston
          rod, may be guided, either approximately or exactly in
          a straight line. --Rankine.
      (b) (Mus.) The ascending or descending of two or more
          parts at fixed intervals, as thirds or sixths.

   Parallel rod (Locomotive Eng.), a metal rod that connects
      the crank pins of two or more driving wheels; -- called
      also couping rod, in distinction from the connecting
      rod. See Illust. of Locomotive, in App. -- Parallel
   ruler, an instrument for drawing parallel lines, so
      constructed as to have the successive positions of the
      ruling edge parallel to each other; also, one consisting
      of two movable parts, the opposite edges of which are
      always parallel.

   Parallel sailing (Naut.), sailing on a parallel of
      latitude.

   Parallel sphere (Astron. & Geog.), that position of the
      sphere in which the circles of daily motion are parallel
      to the horizon, as to an observer at either pole.

   Parallel vise, a vise having jaws so guided as to remain
      parallel in all positions.
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Parallel \Par"al*lel\, n.
   1. A line which, throughout its whole extent, is equidistant
      from another line; a parallel line, a parallel plane, etc.
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            Who made the spider parallels design,
            Sure as De Moivre, without rule or line ? --Pope.
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   2. Direction conformable to that of another line,
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            Lines that from their parallel decline. --Garth.
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   3. Conformity continued through many particulars or in all
      essential points; resemblance; similarity.
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            Twixt earthly females and the moon
            All parallels exactly run.            --Swift.
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   4. A comparison made; elaborate tracing of similarity; as,
      Johnson's parallel between Dryden and Pope.
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   5. Anything equal to, or resembling, another in all essential
      particulars; a counterpart.
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            None but thyself can be thy parallel. --Pope.
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   6. (Geog.) One of the imaginary circles on the surface of the
      earth, parallel to the equator, marking the latitude;
      also, the corresponding line on a globe or map; as, the
      counry was divided into North and South at the 38th
      parallel.
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   7. (Mil.) One of a series of long trenches constructed before
      a besieged fortress, by the besieging force, as a cover
      for troops supporting the attacking batteries. They are
      roughly parallel to the line of outer defenses of the
      fortress.
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   8. (Print.) A character consisting of two parallel vertical
      lines (thus, ) used in the text to direct attention to a
      similarly marked note in the margin or at the foot of a
      page.
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   9. (Elec.) That arrangement of an electrical system in which
      all positive poles, electrodes, terminals, etc., are
      joined to one conductor, and all negative poles, etc., to
      another conductor; -- called also multiple. Opposed to
      series.

   Note: Parts of a system so arranged are said to be

   in parallel or

   in multiple.
      [Webster 1913 Suppl.]

   Limiting parallels. See under Limit, v. t.

   Parallel of altitude (Astron.), one of the small circles of
      the sphere, parallel to the horizon; an almucantar.

   Parallel of declination (Astron.), one of the small circles
      of the sphere, parallel to the equator.

   Parallel of latitude.
      (a) (Geog.) See def. 6. above.
      (b) (Astron.) One of the small circles of the sphere,
          parallel to the ecliptic.
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Parallel \Par"al*lel\, v. t. [imp. & p. p. Paralleled; p. pr.
   & vb. n. Paralleling.]
   1. To place or set so as to be parallel; to place so as to be
      parallel to, or to conform in direction with, something
      else.
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            The needle . . . doth parallel and place itself upon
            the true meridian.                    --Sir T.
                                                  Browne.
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   2. Fig.: To make to conform to something else in character,
      motive, aim, or the like.
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            His life is paralleled
            Even with the stroke and line of his great justice.
                                                  --Shak.
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   3. To equal; to match; to correspond to. --Shak.
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   4. To produce or adduce as a parallel. [R.] --Locke.
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            My young remembrance can not parallel
            A fellow to it.                       --Shak.
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Parallel \Par"al*lel\, v. i.
   To be parallel; to correspond; to be like. [Obs.] --Bacon.
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parallel processing
multiprocessing
multiprocessor
parallel
parallel computing

    (Or "multiprocessing") The simultaneous use of more
   than one computer to solve a problem.  There are many
   different kinds of parallel computer (or "parallel
   processor").  They are distinguished by the kind of
   interconnection between processors (known as "processing
   elements" or PEs) and between processors and memory.  Flynn's
   taxonomy also classifies parallel (and serial) computers
   according to whether all processors execute the same
   instructions at the same time ("single instruction/multiple
   data" - SIMD) or each processor executes different
   instructions ("multiple instruction/multiple data" - MIMD).

   The processors may either communicate in order to be able to
   cooperate in solving a problem or they may run completely
   independently, possibly under the control of another processor
   which distributes work to the others and collects results from
   them (a "processor farm").  The difficulty of cooperative
   problem solving is aptly demonstrated by the following dubious
   reasoning:

   	If it takes one man one minute to dig a post-hole
   	then sixty men can dig it in one second.

   Amdahl's Law states this more formally.

   Processors communicate via some kind of network or bus or a
   combination of both.  Memory may be either shared memory
   (all processors have equal access to all memory) or private
   (each processor has its own memory - "distributed memory")
   or a combination of both.

   Many different software systems have been designed for
   programming parallel computers, both at the operating system
   and programming language level.  These systems must provide
   mechanisms for partitioning the overall problem into separate
   tasks and allocating tasks to processors.  Such mechanisms may
   provide either implicit parallelism - the system (the
   compiler or some other program) partitions the problem and
   allocates tasks to processors automatically or explicit
   parallelism where the programmer must annotate his program to
   show how it is to be partitioned.  It is also usual to provide
   synchronisation primitives such as semaphores and monitors
   to allow processes to share resources without conflict.

   Load balancing attempts to keep all processors busy by
   allocating new tasks, or by moving existing tasks between
   processors, according to some algorithm.

   Communication between tasks may be either via shared memory
   or message passing.  Either may be implemented in terms of
   the other and in fact, at the lowest level, shared memory uses
   message passing since the address and data signals which flow
   between processor and memory may be considered as messages.

   The terms "parallel processing" and "multiprocessing" imply
   multiple processors working on one task whereas "concurrent
   processing" and "multitasking" imply a single processor
   sharing its time between several tasks.

   See also cellular automaton,symmetric multi-processing.

   Usenet newsgroup: <news:comp.parallel>.

   <Institutions>,
   <research groups>.

   (2004-11-07)