1. shifts & rotations
Robert,
I believe multiplies as well as floored divides by 2 are optimized. Since we
do not have fast, native shifts in Euphoria, are multiplies and divides by
integral powers of 2 similarly optimized?
If not, why not?
Thanks. jiri
2. Re: shifts & rotations
I seem to recall that they are. I believe that RC said so himself self
when he introduced those optimizations a long time ago.
Lucius L. Hilley III - Unkmar
----- Original Message -----
From: "jiri babor" <jbabor at paradise.net.nz>
To: <EUforum at topica.com>
Subject: shifts & rotations
>
>
> Robert,
>
> I believe multiplies as well as floored divides by 2 are optimized. Since
we
> do not have fast, native shifts in Euphoria, are multiplies and divides by
> integral powers of 2 similarly optimized?
> If not, why not?
>
> Thanks. jiri
>
>
>
> TOPICA - Start your own email discussion group. FREE!
>
>
3. Re: shifts & rotations
jiri babor wrote:
> I believe multiplies as well as floored divides by 2 are optimized.
Yes.
> Since we
> do not have fast, native shifts in Euphoria, are multiplies and divides by
> integral powers of 2 similarly optimized?
Only 2. Not 4, 8, 16, ...
> If not, why not?
- there's already complicated code to determine if
an integer*integer multiply might exceed 31 bits
(and have to be converted to floating-point).
I'm reluctant to add more special cases.
- C shifts are not completely portable across all machines
- In the Pentium 4, shifts use more cycles (4) than they
used to (1), so you don't gain a lot by replacing
multiplies or divides with shifts.
Regards,
Rob Craig
Rapid Deployment Software
http://www.RapidEuphoria.com
