Implementation of pow(3m) function
Doug Gwyn
gwyn at smoke.BRL.MIL
Sat Aug 4 07:21:40 AEST 1990
In article <1990Aug2.120706.25713 at bnrgate.bnr.ca> mleech at bcarh342.bnr.ca (Marcus Leech) writes:
>I'm wondering about the efficiency of "standard" implementations of this
> (and other) math library functions for C. Does pow(3m) conventionally
> use a logarithm table, or is it (ugh!) iterative, or some B.O.T?
All common implementations of pow(x,y) basically perform exp(log(x)*y),
but they add some twists designed to avoid unnecessary overflow, or in
the case of 4.3BSD, to implement the IEEE FP funny numbers. Thus there
is often a considerable amount of additional bookkeeping computation
beyond the log() and exp() evaluations that one would expect.
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