Re: 64-bit subtract from vector unsigned int
Le mer. 8 avr. 2020 à 11:56, Jeffrey Walton <noloader@gmail.com> a écrit :
> As old as the hardware is (circa 2000), that old PowerPC chip
> outperforms some modern hardware, like Atoms, Celerons and low-end ARM
> cpu's in modern gadgets.
They don't feel that fast anymore... Even a Raspberry Pi 3 will run
circle around my dual-1.25 GHz G4 (not that much faster per-core, but
there's 4 of them), and even more so for the single G4. And a Rpi4 is
even faster per-core. And while the PATA interface is faster than the
SD card of the Pi, it's not that great for I/O either. And they don't
have that much memory, either. The G5 is a whole different beast (I
have a quad, complete with the full complement f 16 GiB of ECC RAM,
just because I can).
> Testing some algorithms, like Simon-128 and Speck-128, show a need for
> Altivec. For example, Integer-based Speck-128 was running at about 70
> cpb. Altivec-based Speck-128 dropped to 10 cpb even with me doing all
> the 64-bit fixups. (Speck-128 runs around 2.5 cpb when the native
> hardware supports 64-bit operations, like on Power8).
Interesting. Maybe you could share your implementations in the
Supercop benchmark? (<http://bench.cr.yp.to/supercop.html>, there's
some help in "How to submit new software:").
Are you interested in just those algorithms or crypto in general? I
have an AltiVec implementation of Chacha20 in there that can probably
be beaten if you feel up to the challenge ;-)
(unfortunately, no published results on G4 or recent one on G5 as
Supercop takes forever to run, and I've already blown a power supply
on my G5 so I'm reluctant to let it run for extended period of time).
Cordially,
--
Romain Dolbeau
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