strength reduction
An optimisation where a function of some systematically changing variable is
calculated more efficiently by using previous values of the function. In a
procedural language this would apply to an expression involving a loop variable
and in a declarative language it would apply to the argument of a recursive
function. E.g.
f x = ... (2**x) ... (f (x+1)) ...
==>
f x = f' x (2**x)
where
f ' x z = ... z ... (f' (x+1) 2*z) ...
Here the expensive operation (2**x) has been replaced by the cheaper 2*z
in the recursive function f'. This maintains the
invariant that z = 2**x for any call to f'.
(1995-01-31)
Nearby terms:
Streaming SIMD Extensions « stream-oriented «
STREAMS «
strength reduction » STRESS » stress testing »
strict
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