Anders Henriksson wrote:
> 
> <This may be a bit late for the original writer, but this text
>  wouldn't have helped him anyway...>
> 
> lyonstb <lyo### [at] pacbellnet> wrote:
> >yes I understand that it is single threaded but don't you think that number
> >crunchin code (like povray) would run faster on a computer that was built for
> >utra fast number crunching??? or has povray been so influenced by the intel
> >world that the code/algorithm has a "speed limit"?
> 
> You have to see the difference between number crunching and number
> crunching. While povray is very computing intensive it is not built
> along the lines of most number crunching code out there. Many high-end
> computers, such as Cray T90 and SV1, derive their main computing
> power from their vector units. If the code is not adapted for vector
> units, tough luck, because then your computing grinds to a halt.
> 
> Other posters have claimed "bad compiler", which in part is true. Sadly
> enough it's awfully hard to make the compiler do the vectoring for you,
> just like it's hard to create parallellized machine code from standard
> sequential source code. Vectorized code is even harder to derive
> automatically. As povray is sequential, the original poster is out
> of luck.
> 
> Raytracing as such, however, may possibly[1] be vectorized. That would
> of course require a (more or less) ground up redesign in order to
> maximize vectorization.[2]
> 
> /Anders
> [1] I can't say I'm sure, but I can't see any reason why not.
> [2] In most vector machines, speed difference between vectorized and
>     non-vectorized code is somwhere in the 10^2-10^3 range, iirc.

I've done some more reading since my last response, and I suspect that
one or more of the existing unofficial parallel versions of POV-Ray
might take good advantage of a Cray, but I don't have a Cray sitting
around with which to test this hypothesis.  It's not specifically tuned
for a Cray, but Cray versions of some message passing libraries are, and
it may be sufficient to put the proper library calls in the right
places.

-Mark Gordon

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