On Fri, Jan 19, 2018 at 6:13 PM Nathaniel Smith <n...@pobox.com> wrote:
> ... > I agree that relaxing our policy would be better than the status quo. > Before making any decisions, though, I'd like to make sure we > understand the alternatives and their trade-offs. Specifically, I > think the main alternative would be the following approach to > versioning: > > 1) make RandomState's state be a tuple (underlying RNG algorithm, > underlying RNG state, distribution version) > 2) zero-argument initialization/seeding, like RandomState() or > rstate.seed(), sets the state to: (our recommended RNG algorithm, > os.urandom(...), version=LATEST_VERSION) > 3) for backcompat, single-argument seeding like RandomState(123) or > rstate.seed(123), sets the state to: (mersenne twister, > expand_mt_seed(123), version=0) > 4) also allow seeding to explicitly control all the parameters, like > RandomState(PCG_XSL_RR(123), version=12) or whatever > 5) the distribution functions are implemented like: > > def normal(*args, **kwargs): > if self.version < 3: > return self._normal_box_muller(*args, **kwargs) > elif self.version < 8: > return self._normal_ziggurat_v1(*args, **kwargs) > else: # version >= 8 > return self._normal_ziggurat_v2(*args, **kwargs) > I like this suggestion, but I suggest to modify it so that a zero-argument initialization or 1-argument seeding will initialize to a global value, which would default to backcompat, but could be changed. Then my old code would by default produce the same old results, but adding 1 line at the top switches to faster code if I want.
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