Dominic Steinitz:
> Malte Milatz:
> > http://hpaste.org/1695#a2
> >
> > It performs better than the SHA1 algorithm in Crypto: It is faster by a
> > factor of approximately e. It is also competitive (regarding time)
> > with the »unsafe« SHA1 implementation posted here some days ago,
>
> Great. Can you post some timings?
On a 12 MB file I get
malte +RTS -prof -RTS
total time = 9.80 secs (196 ticks @ 50 ms)
total alloc = 3,764,831,396 bytes
anatoly +RTS -prof -RTS
total time = 14.35 secs (287 ticks @ 50 ms)
total alloc = 1,773,131,228 bytes
crypto +RTS -prof -RTS
total time = 24.55 secs (491 ticks @ 50 ms)
total alloc = 8,703,970,360 bytes
> > although it uses considerably more memory. Of course, you may safely
>
> Does it have a space leak or does it run in constant but larger space than the
> other versions?
I haven't discovered a space leak so far. When profiling with -S, the
first column holds fairly constant values.
> > forget it if you're interested in performance near a C implementation
> > such as GNU sha1sum.
> I don't think it's unreasonable to think we could get near to C performance
> and
> we've been getting closer.
Hm, but I suppose, if we want the code to remain in its pure style, that
will mean that someone of the more clever Haskell people has to invent
again a low-level library that improves performance behind the curtains.
On the other hand, we can still hope for someone to find a better
algorithm.
> PS I had a 5 minute (well actually less) look at the code and it doesn't look
> dissimilar to other versions I've seen in Haskell. I wonder if the speedup is
> principally because of ByteString.
Before I started tweaking (with the help of the IRC channel), I had read
the input in as a ByteString, then unpacked it to [Word8] for further
processing. That version can be found on top of the same hpaste page.
It delivers:
malte_old +RTS -prof -RTS
total time = 15.95 secs (319 ticks @ 50 ms)
total alloc = 5,844,911,772 bytes
This is still better than crypto. (By the way, I'm really astonished by
this. I translated the SHA1 specification into Haskell, and as it seems
so far, I'm better than a library. That's worth a party!)
> PPS We have to put splitn in a library.
Yea. It's disappointing not to find it in Data.List. However, splitByN
might yet be a better name.
Regards, Malte
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