[viff-devel] Confusing behaviour?

[Martin Geisler]

Thomas P Jakobsen <thomas.jak at gmail.com> writes:

> By the way, the same thing seem sto happen if the protocol, insted of
> asking the user to press enter, does some local computations like
> quering a database, sleeping, computing primes or the like. [...]

Right -- callback functions *cannot block*! They must always returns
very quickly and use some asynchronous mechanism to signal when a
long-running operations is finished. See this FAQ:

  http://twistedmatrix.com/trac/wiki/FrequentlyAskedQuestions#HowdoIuseDeferredstomakemyblockingcodenon-blocking

Twisted has a database abstraction layer that does this for databases:

  http://twistedmatrix.com/projects/core/documentation/howto/rdbms.html

And a threadpool for more general tasks:

  http://twistedmatrix.com/projects/core/documentation/howto/threading.html

For non-blocking access to stdin and stdout there is the
twisted.internet.stdio module, see:

  http://twistedmatrix.com/trac/browser/trunk/doc/core/examples/stdiodemo.py

This means that your example should look similar to this:

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-- 
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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