On Sat, Mar 07, 2015 at 09:06:13PM +0100, Floris van Manen wrote:
> I'm using the jumpahead() to have multiple streams in parallel,
> derived from a single point.
I'm afraid I don't understand what that sentence means. Do you mean
derived from a single seed?
If so, I think the easiest way is to just create multiple random
instances. Suppose you want five streams of random numbers: create one
extra "seeder" (or just use the pre-defined top-level random functions):
import random
seeder = random.Random(myseed) # or just use random.seed(myseed)
streams = [random.Random(seeder.random()) for _ in range(5)]
If you want to reset them to the initial state, just
reseed the seeder stream and recreate them. Or you can just grab all
their internal states:
states = [s.getstate() for s in streams]
> def jumpRandomState(self):
> self.random.setstate(self.randomState)
> self.random.jumpahead(1)
> self.randomState = self.random.getstate()
I'm afraid I don't understand the purpose of that method or why you are
restoring the internal state before jumping. I tried putting it in a
subclass of random.Random, but it raises an exception:
py> class MyRandom(random.Random):
... def jumpRandomState(self):
... self.random.setstate(self.randomState)
... self.random.jumpahead(1)
... self.randomState = self.random.getstate()
...
py> rnd = MyRandom(1000)
py> rnd.jumpRandomState()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in jumpRandomState
AttributeError: 'builtin_function_or_method' object has no attribute
'setstate'
so your code doesn't work for me.
Based just on the name, I would do this:
class MyRandom(random.Random):
def jumpRandomState(self):
self.jumpahead(356789)
If you don't trust jumpahead to reliably jump to an independent part
of the PRNG sequence, re-seed with an independent pseudo-random number:
class MyRandom(random.Random):
_JUMPER = random.Random()
def jumpRandomState(self):
self.seed(self._JUMPER.random())
--
Steve
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