Folks,
I think your precious time is better spent on figuring out a brilliant
solution to handling memory issues with VIFF, than on discussions about what
"asynchronous" really means :-)
regards, Ivan
Quoting Marcel Keller <mkel...@cs.au.dk>:
A really unpleasant thought has occurred to me: Is VIFF really properly
asynchronous? (Yes, this question is intended to provoke you into thinking
about the issue below. Of course VIFF is asynchronous in the sense that
there are no rounds.)
If I understand/remember correctly, VIFF is 100% single threaded. This
means that if we have a small program:
x, y = runtime.shamir_share([1, 2], Zp, input)
z = x*y
for i in xrange(100):
z=z*z
1) We first share two values (returning immediately).
There's a pitfall here: What do you mean with "share"? At this point, the
shares are only scheduled to be sent, the real communication doesn't occur
until step 3. The FAQ of Twisted says so:
http://twistedmatrix.com/trac/wiki/FrequentlyAskedQuestions#WhydoesittakealongtimefordataIsendwithtransport.writetoarriveattheothersideoftheconnection
Since I discussed this issue last week with Martin, I also looked at the
source of Twisted 8.1.0 to confirm it.
2) We start doing a lot of multiplications. However, as we don't have
the actual shares yet, we just get deferreds.
3) Once the for-loop terminates, we return control to the
surroundings. At this point we notice that the shares of x and y are
there and start the actual multiplication protocols.
Is my interpretation above correct? Because if it is, then this really
explains the memory issues I've been seeing. And more importantly, it
tells us how to actually use VIFF for large-scale computation: put in
explicit "stops".
As Mikkel wrote, I had the same issues and I solved them by calling parts of
my code (one AES round at a time) as a callback of some trigger shares.
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