This is interesting. On my Athlon XP 2000+ the CPU usage
goes straight to 100% and stays there until the image is done.
At least with the AMD processor Windows XP reports
accurately ;-)

H

"Warp" <war### [at] tagpovrayorg> wrote in message
news:4187ff7e@news.povray.org...
> regdo <reg### [at] wanadoofr> wrote:
> > Do you mean there is no way for POV to use the whole power of the
processor
> > and we have to wait twice the time we should ? Rats !
>
>   Didn't you read what he said?
>
>   P4 is just one processor, not two, and POV-Ray is using (almost) 100% of
> its power.
>   You will not get basically any advantage by rendering in two threads
> because the two threads will mostly be interleaved by the CPU, not run
> in parallel.
>   That is, in other words: Even if you run two instances of POV-Ray,
> each one rendering half of the image, the total rendering time will
> not speed up considerable. One instance is already using the maximum
> capacity of the CPU.
>
>   Now, P4 has this funny thing called hyperthreading which makes the
> processor look like two and can, with some tricks, be used to speed up
> a program (almost as if it was run by two true processors). The trick
> is to create two threads and run eg. integer math in one (calculated
> by the ALU) and floating point math (calculated by the FPU) or MMX math
> (calculated by the MMX processor) in the other.
>   However, POV-Ray can hardly use this trick even if it wanted to because
> most of what it does is floating point math, and there's only one FPU to
> do it. And POV-Ray *is* running through the FPU at full power.
>
>   Windows makes it look like it is only using 50% of CPU because P4 is
> emulating two CPUs and Windows makes a simple (but basically wrong)
> calculation about how much of the two (virtual) processors POV-Ray is
> using. POV-Ray cannot use the "other processor" because there's no
> other processor. It's just a kind of "virtual" processor (which another
> process not needing the FPU could perhaps use).
>
>   So no, if the POV-Ray benchmark is being finished in 30 minutes in
> your P4, there's no way it can finish in 15 minutes no matter what you
> do. That's not what the "two processors" mean.
>
> -- 
> #macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb
M()}}
> N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
> N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  -
Warp -

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