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From "Maksim Ananjev" <maksim.anan...@gmail.com>
Subject Re: [perf] Comparative benchmarking
Date Wed, 07 Nov 2007 09:03:12 GMT
Btw, why not to implement api magic that would substitute sqrt(x) by
hardware sse sqrt instruction? "sqrtpd", afair

It might be faster then JNI call.

Just an idea. I am not sure if such JIT hack looks pretty from the
point of view of design.


2007/11/7, Egor Pasko <egor.pasko@gmail.com>:
> On the 0x387 day of Apache Harmony Aleksey Shipilev wrote:
> > On 07 Nov 2007 00:27:25 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
> > > Vladimir, guess what? :) I actually mixed several things
> > > altogether.
> > <giggly>(sigh) As usual, miracle does not happen :) I dreamed to see
> > software sqrt() implementation that could be faster than hardware one.
> > </giggly>
> >
> > > So, we are left with SSE asm that can be inlined by JIT and AFAI can
> > > see it is not as fast as HotSpot? Weird :)
> > No, for now we have just the intrinsic in native code, so we also have
> > overheads for JNI transition (and it is heavy!), parameter passing,
> > chains of calls, etc. I believe that sqrt() magic will lead that NBody
> > performance very close to RI.
>
> Ha! I thought, you made it without JNI. Then we have a chance! If we
> do not get it through magics we still have another chance to implement
> 1/sqrt() :)
>
> > BTW, in my thought this benchmark is like the top of the iceberg
> > called "FP performance problems".
>
> Yes, I know, DRLVM has not been actively optimized for FP calc.
>
> --
> Egor Pasko
>
>
>


-- 
Maksim

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