RE: [computer-go] Pattern Matcher

["Mark Boon" <tesuji@xxxxxxxxx>]

> -----Original Message-----
> From: computer-go-bounces@xxxxxxxxxxxxxxxxx
> [mailto:computer-go-bounces@xxxxxxxxxxxxxxxxx]On Behalf Of Vincent
> Diepeveen
> Sent: Tuesday, November 09, 2004 12:05
> To: computer-go; computer-go
> Subject: RE: [computer-go] Pattern Matcher
>
>
> At 11:54 9-11-2004 -0200, Mark Boon wrote:
> >
> >
> >> -----Original Message-----
> >> From: computer-go-bounces@xxxxxxxxxxxxxxxxx
> >> [mailto:computer-go-bounces@xxxxxxxxxxxxxxxxx]On Behalf Of Frank de Groot
> >> Sent: Tuesday, November 09, 2004 11:49
> >> To: computer-go
> >> Subject: Re: [computer-go] Pattern Matcher
> >>
> >>
> >> From: "John Tromp" <John.Tromp@xxxxxxxxxxxxxxxxx>
> >> Subject: Re: [computer-go] Pattern Matcher
> >>
> >>
> >>
> >> > It uses 2 modulo operations per lookup.
> >> >
> >> > > modulo and divide are like a 46+ cycles at opteron, and like
> >> 200 cycles
> >> or
> >> > > so at a P4?
> >> >
> >> > What can I say, P4s suck:-(
> >>
> >>
> >> Why don't you use an AND?
> >> Vincent already mentioned that.
> >> A simple AND is the same as a modulo, n'est-ce pas?
> >
> >Yes. Provided you use a power of two. But the speedup should
> show both in C
> >and in Java. If anything I'd think it would close the
> performance gap rather
> >than making it bigger. Maybe worth a try.
>
> Simple math shows the oppostie Mark.
>
> Suppose you have 2 instances:
>
> J
> C
>
> Let's assume J = 2.6
> Let's assume C = 2.0
>
> So 30% speed difference in favor C.
>
> Now we remove from both 1.5, as it gets faster.
>
> J ==> 1.1
> C ==> 0.5
>
> Now J is slower : 1.1 / 0.5 = 2.2 times
>

You're right about your math, if that's really how it turns out. Whichever
way, I still consider all of this just talk. Why not prove it? Make it run 3
times faster.

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