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Re: Power of two round up.

by Dominus (Parson)
on Dec 16, 2000 at 22:24 UTC ( #47061=note: print w/ replies, xml ) Need Help??

in reply to Re: Power of two round up.
in thread Power of two round up.

I'm amazed at how clever this is, and I'm going to use it in my program. Thanks a lot.

Comment on Re: Power of two round up.
Re: Re: Power of two round up.
by I0 (Priest) on Dec 17, 2000 at 05:29 UTC
    Although it's a technique more appropriate in a C program. In Perl, log($_)/log(2) benchmarks faster. (assuming it rounds properly at the boundaries)
    Update: My earlier timethese qq{} may have been misleading. With timethese sub{} the | >> method comes out faster
      Sure, because it has to dispatch many fewer opcodes. But if I had wanted to use the log2 x solution, I wouldn't have asked in the first place. Floating-point arithmetic gives me the heebie-jeebies.

        Floating-point gives me heebie-jeebies too. (in fact, a floating conversion seems to be what makes the |>> method fail for @_ = (0)
        --then again, log(0) doesn't work either, and the |>> method does work for @_=(0) if you use integer;)
        P.S. Why does an opcode fetch take longer than a transcendental function? I'm sure that part of the interpreter must have been fully optimized.

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