[issue12754] Add alternative random number generators

[douglas bagnall]

douglas bagnall <douglas at paradise.net.nz> added the comment:

Earlier this year I wrote Python wrappers for a number of generators:

https://github.com/douglasbagnall/riffle

They are mostly cryptographic stream ciphers from the ESTREAM[1] project, but I was also interested in dSFMT[2], which is a SIMD optimised descendant of MT19937 which runs several times faster and directly produces doubles using cunning bit tricks.

[1]http://www.ecrypt.eu.org/stream/
[2]http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/#dSFMT

Wrapped in Python, the stream ciphers ran about as fast as MT19937 on my laptop, while dSFMT took about two thirds the time to run a "random();random();random();..." test.  For a slightly more realistic test ("sum(random() for x in range(N))"), the performance levelled right off.  As expected.

The stream cipher generators have some good properties.  They generally generate random bytes using something analogous to hash('%s%s' % seed, counter), which means different seeds produce well separated streams, and to skip forward or back in the stream, you just adjust the counter.  This would allow the reinstatement of Random()'s stream-skipping function, which some people (e.g. L'Ecuyer) think is important. (incidentally, the MT people have come up with a jump-ahead algorithm for MT http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/JUMP/index.html).

Of the ciphers I tried, the chacha/salsa family and sosemanuk had the best combination of good testing and portable, reasonably fast, openly licensed C implementations.  HC128 and snow2 also perform well.

The chacha code is shorter than sosemanuk, so I would choose that.  It is used as a primitive in the BLAKE SHA3 candidate, which is a vote of confidence and an attractor of testing for the algorithm.

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nosy: +dbagnall

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