[viff-devel] Broken build!

[Martin Geisler]

Hi everybody,

The build is broken:

  http://buildbot.viff.dk/waterfall

Janus, you added this code to benchmark.py:

  def update_args(runtime, options):
  args = {}
  if options.args != :
  for arg in options.args.split(','):
  id, value = arg.split('=')
  args[id] = long(value)
  runtime.setArgs(args)
  return runtime

What is that supposed to do? We don't have a setArgs method anywhere,
and we don't use the Java-like CamelCase coding style anyway. You're not
trying to parse the command line, right? (we have optparse for that)

-- 
Martin Geisler

VIFF (Virtual Ideal Functionality Framework) brings easy and efficient
SMPC (Secure Multiparty Computation) to Python. See: http://viff.dk/.
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Re: [viff-devel] Broken build!

[Janus Dam Nielsen]

Hi everybody,


The build is broken:


That is unfortunate, thanks for notifying. I will fix it as soon as  
possible.



Janus, you added this code to benchmark.py:

 def update_args(runtime, options):
 args = {}
 if options.args != :
 for arg in options.args.split(','):
 id, value = arg.split('=')
 args[id] = long(value)
 runtime.setArgs(args)
 return runtime

Yes I did.


What is that supposed to do?
It is supposed to be a way for providing arguments for runtimes, which  
are unique for a given runtime.



We don't have a setArgs method anywhere,
If you use the --args commandline argument then it is your  
responsibility that the runtime you use has a proper setArgs method.



and we don't use the Java-like CamelCase coding style anyway.

Right, I will change that, as soon as possible.

You're not trying to parse the command line, right? (we have  
optparse for that)
I believe that the commandline arguments should be general to all  
runtimes.




Janus Dam Nielsen

Research and Innovationspecialist, PhD.
CENTRE FOR IT-SECURITY

THE ALEXANDRA INSTITUTE LTD.

T +45 42 22 93 56
E janus.niel...@alexandra.dk
W alexandra.dk


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Re: [viff-devel] Optimizing preprocessing

[Janus Dam Nielsen]

Hi Marcel,

I am not opposed to your suggestion. However I would like to point out  
that in VIFF you compute on shares and not field elements!. Computing  
directly on the field elements is hacking the abstractions of VIFF.
Computation on field elements or rather the representation of a Share  
can be useful as an optimization, however this optimization should be  
confined within applications or runtimes, and should not progress over  
interface boundaries as I fear you are suggesting.



On 08/10/2009, at 20.11, Marcel Keller wrote:


Dear friends of VIFF,

I have a proprosal to optimize preprocessing in VIFF, which I would  
like to put up for discussion.


Notation:
- D(x): a Deferred object whose callback function will be called  
with x

- S(x): same for a Share object
- F: a FieldElement object
- [x, ...]: a Python list
- (x, ...): a Python tuple

Current situation:
The two generate_triples() functions in the active runtimes return
n, D([(S(F), S(F), S(F)), ...]),
where n denotes the length of the list. Runtime.preprocess() puts  
one D(S(F), S(F), S(F)) per program counter in the preprocessing  
pool and uses util.deep_wait() to return a Deferred whose callback  
is called when all field elements are available.


The get_triple() functions return
D(S(F), S(F), S(F)),
either taken from the preprocessing pool, or by calling  
generate_triples() and adding an extra callback to extract the first  
triple.


My proposal:
The generate_triples() functions return
[D([F, F, F]), ...],
and Runtime.preprocess() puts one [F, F, F] per program counter in  
the preprocessing pool. There is no need for deep_wait, we can just  
use gatherResults on the Deferreds return by the generator  
functions. The generator functions can use gatherResults to get  
D([F, F, F]) from [S(F), S(F), S(F)].


The get_triple() functions return
[F, F, F], True  if there is a triple in the pool, and
[S(F), S(F), S(F)], Falseotherwise.
For the multiplication in BasicActiveRuntime it doesn't make a  
difference whether FieldElements or Shares are returned. Future  
applications which require Shares can wrap the FieldElements in  
Shares if the Boolean is True.


Benchmarks:
- 1 multiplications in parallel with active security using PRSS
 - 4% faster preprocessing
 - 5% faster online operation
 - 50 MB less memory used
- 10 AES blocks in parallel using masked exponentiation with active  
security using PRSS

 - 10% faster preprocessing
 - 10% faster online operation
 - 140 MB less memory used

Further considerations:
- I don't see any problem for replacing FieldElement with anything  
that does not contain Deferreds in any form.
- Probably, it would also be possible to leave the generator  
functions as they are and use something similar to deep_wait().  
However, I consider it as an overhead.
- One could also always wrap the FieldElements in Shares, but this  
would again be an overhead.


Best regards,
Marcel
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Janus Dam Nielsen

Research and Innovationspecialist, PhD.
CENTRE FOR IT-SECURITY

THE ALEXANDRA INSTITUTE LTD.

T +45 42 22 93 56
E janus.niel...@alexandra.dk
W alexandra.dk


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