parallelism
1. parallel processing.
2. <parallel> The maximum number of independent subtasks in a given task
at a given point in its execution. E.g. in computing the expression
(a + b) *
(c + d) the expressions a, b, c and d can all be calculated in parallel
giving a degree of parallelism of (at least) four.
Once they have been evaluated then the expressions a
+ b and c + d can be calculated as two independent
parallel processes.
The Bernstein condition states that processes P and Q can be executed in
parallel (or in either sequential order) only if:
(i) there is no overlap between the inputs of P and the outputs of Q and vice
versa and
(ii) there is no overlap between the outputs of P, the outputs of Q and the
inputs of any other task.
If process P outputs value v which process Q reads then P must be executed
before Q. If both processes write to some variable then its final value will
depend on their execution order so they cannot be executed in parallel if any
other process depends on that variable's value.
(1995-05-07)
Nearby terms:
Parallel FORTH « Parallel Fortran « Parallel Haskell
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parallelism » Parallel Pascal » parallel port »
Parallel Presence Detect
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