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Online Computer Terms Dictionary - F

finite differencing ==>

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Here the expensive operation (2**x) has been replaced by the cheaper 2*z in the recursive function f'.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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