Re: [Ocaml-lib-devel] write_double

[Florent M. <fmo...@li...>]

> with this change, I still get roughly 2 million ops (only slightly faster).
> This would lead me to believe that time is not spent in doing ALU ops but
> rather time is spent either in the garbage collector or data cache misses.

Have you tryed my (write_double_opt) version in your benchs to compare?
How much was the difference?

and if time is spent more in allocs and GC, this explains too why 
(write_double_opt) is 3 times faster: it doesn't alloc anything.

> Isn't there a way to perform the same double_cast using some GC/Ocaml
> object structure magic like the Obj module?

I haven't found any ocaml function equivalent to the C function memcpy() even 
in the Obj module.


> How fast does a write_double have to be?

Yes I admit happily that this is a geekish issue :)
but we are geeks and love trying to optimise code ;-)

Well more seriously if I had found a speedup of only 5% or 10% I wouldn't have 
bother you. If I decided to write it's because an enhancement of close to 3 
times faster was not that bad.
But with a (String.create) to make it thread safe, the enhancement is only 
about 2.5 times faster.

-- 
With Regards
Florent