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Re: RE: sieve of Eratosthenes

by cforde (Monk)
on May 19, 2001 at 04:23 UTC ( #81667=note: print w/replies, xml ) Need Help??

in reply to RE: sieve of Eratosthenes
in thread sieve of erothenes

In the pursuit of efficiency I have come up with a slightly different implementation: Carl1. In Carl2 I tried to optimize at the expense of a few more characters.

On my WinNT PIII 800Mhz machine with ActiveState 522 both of these are faster than ase's Bit Vector implementation.

Carl1: @p=(1);for(2..10000){if(!$n[$_]){push@p,$_;for($k=$_*$_;$k<=10000; +$n[$k]=1,$k+=$_){}}} Carl2: @p=(1,2);for($_=3;$_<=10000;$_+=2){if(!$n[$_]){push@p,$_;for($k=$_ +*$_;$k<=10000;$n[$k]=1,$k+=$_){}}}
One thing that I found interesting is that for n less than about 10,000, Carl1 is significantly faster than Carl2. The loop control overhead must be pretty significant.

Have fun,
Carl Forde

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[ambrus]: My boss wants to generate output data that is impossible to compute from the inputs we have. And I'm trying to convince him that he shouldn't do that.
[Corion]: ambrus: He isn't familiar with GIGO (or nIGO) yet?
[Corion]: Also, is it impossible in the general case, but doable in your specific case, maybe? I find that working through a counterexample usually makes people see the light

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