[Haskell-cafe] Annoyed at System.Random
tab at snarc.org
Fri May 4 16:11:24 CEST 2012
On 05/04/2012 02:37 PM, Ryan Newton wrote:
> My end goal is to have the user use transparently the fastest
> implementation available to their architecture/cpu providing they use the
> high level module. I've uploaded the cpu package which allows me to detect
> at runtime the aes instruction (and the architecture), but i've been
> distracted in implementing fast galois field arithmetics for GCM and XTS
> mode (with AES).
> Yes! A worthy goal!
> I think the proposal here is that we do the build/integration work to get
> something good which is portable enough and install-reliable enough to replace
> 'random'. Then people who don't care will be using a good implementation by
> That was my goal when I had my own small shot at this, but what I came up with
> was *very* build-fragile. (Depended on assembler being available, or on
> prebuilt binaries being included for that package.) You can see the Setup.hs
> customization I attempted to do in intel-aes to compensate, but it's not enough.
> Can we write a cabal-compatible, really robust installer that will test the
> users system and always fall back rather than failing?
That was my original plan, until i find out that it's not really possible.
For the language, i think assembly is a no-no with cabal, as such it need to be
embedded in gcc inline assembly if you want to have something that works (unless
there's a secret way to run assembler in a portable fashion in cabal).
Which is the reason behind why i settled on intrinsics, as i didn't have to do
the assembly directly. It appears more portable as well
as every major compiler seems to support it (with difference of course, it would
too simple otherwise (!))
> P.S. How are you doing the CPUID test for NI instructions? I used the *intel
> provided* test for this (in intel-aes) but I still had reports of incorrect
> identification on certain AMD CPUs...
I haven't done it yet, but it should be just a matter of this piece of code for
Intel and AMD:
supportAESNI :: IO Bool
supportAESNI = cpuid 1 >>= \(_,_,ecx,_) -> ecx `testBit` 25
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