sympy: what's wrong with this picture?

[Nanjundi]

On Mar 5, 3:34 pm, Mensanator <mensana... at aol.com> wrote:
> On Mar 5, 9:29 am, Nanjundi <nanju... at gmail.com> wrote:
>
> > On Mar 4, 3:13 pm, Mensanator <mensana... at aol.com> wrote:
>
> > > On Mar 4, 12:32 pm, Nanjundi <nanju... at gmail.com> wrote:
>
> > > > Does seeding ( random.seed ) random with time fix this? It should.
>
> > > I suppose that depends on how long it takes factorint() to
> > > process a number. If the seed is reset before the next clock
> > > tick, you will get the same random numbers as the previous
> > > iteration.
>
> > Alright, then make it constant and don't worry about the clock tick.
>
> Reseeding with a constant always sets the sequence to the same
> starting
> point.
>

Right, not a good idea.

>
>
> >>> for i in xrange(10):
>
> > ...   f1 = random.choice(f)
> > ...   print f1,
> > ...   f2 = random.choice(f)
> > ...   print f2,
> > ...   C = f1*f2
> > ...   ff = None
> > ...   ff = sympy.factorint(C)
> > ...   print ff
> > ...   random.seed(i)
> > ...
> > 5573 5171 [(5171, 1), (5573, 1)]
> > 8537 7673 [(7673, 1), (8537, 1)]
> > 2063 8573 [(2063, 1), (8573, 1)]
> > 9551 9473 [(9473, 1), (9551, 1)]
> > 2909 5659 [(2909, 1), (5659, 1)]
> > 2897 1789 [(1789, 1), (2897, 1)]
> > 6361 7541 [(6361, 1), (7541, 1)]
> > 8017 8293 [(8017, 1), (8293, 1)]
> > 3671 2207 [(2207, 1), (3671, 1)]
> > 2803 9629 [(2803, 1), (9629, 1)]
>
> > > Frankly, I don't understand why factorint() reseeds at all.
>
> > Read the doc:
> > *    The rho algorithm is a Monte Carlo method whose outcome can be
> > affected by changing the random seed value.  *
>
> But that doesn't give it the right to mess with the state
> of the random number generator _I'm_ using. Had I actually
> known what was happening, I could have saved the state of
> my random number generator s=random.getstate() and then restored
> it after calling factorint(), random.setstate(s).
>
> import sympy   # with RK's patch removed
> import time
> import random
>
> f = [i for i in sympy.primerange(1000,10000)]
>
> for i in xrange(10):
>   f1 = random.choice(f)
>   print f1,
>   f2 = random.choice(f)
>   print f2,
>   C = f1*f2
>   ff = None
>   rs = random.getstate()
>   ff = sympy.factorint(C)
>   random.setstate(rs)
>   print ff
>
> 5669 3863 [(3863, 1), (5669, 1)]
> 1973 5431 [(1973, 1), (5431, 1)]
> 7577 6089 [(6089, 1), (7577, 1)]
> 8761 4957 [(4957, 1), (8761, 1)]
> 4153 2719 [(2719, 1), (4153, 1)]
> 4999 5669 [(4999, 1), (5669, 1)]
> 8863 5417 [(5417, 1), (8863, 1)]
> 7151 7951 [(7151, 1), (7951, 1)]
> 7867 9887 [(7867, 1), (9887, 1)]
> 9283 5227 [(5227, 1), (9283, 1)]
>
> Of course, this is new as of Python 2.4, so if factorint()
> tried to save & restore state, sympy wouldn't work on Python
> 2.3 or earlier.
>
> If I'm reading RK's patch correctly, he doesn't reseed the
> random number generator, he creates a new random object that
> maintains it's own state that can be freely seeded to any
> value without disturbing the state of my random number generator.
>
>
>
> > > Doesn't Random automatically initialize the seed?
> > > Doesn't constantly reseeding degrade the performance of the
> > > random number generator? With Robert Kern's patch, the reseeding
> > > is no longer a constant, fixing the immediate symptom.
>
> > Does it matter?
>
> I was wrong. It is a constant, just not 1234. If that's what
> factorint() needs, fine. As long as it maintains a seperate state
> than the one I'm using.
>
> > The factorint reseeds using a constant seed (1234).
>
> Not now it doesn't:

:)

>
> @@ -92,8 +92,8 @@ def pollard_pm1(n, B=10, seed=1234):
>
>      """
>      from math import log
> -    random.seed(seed + B)
> -    a = random.randint(2, n-1)
> +    prng = random.Random(seed + B)
> +    a = prng.randint(2, n-1)
>      for p in sieve.primerange(2, B):
>          e = int(log(B, p))
>          a = pow(a, p**e, n)
>
>
>
> > > But what if _I_ wanted to make a repeatable sequence for test
> > > purposes? Wouldn't factorint() destroy my attempt by reseeding
> > > on every call?
>
> > Repeatable sequence? save it and reuse!
>
> As part of my resolution to tone down my attitude,
> I won't even reply to that.
>
Thanks.

> > Think about "What if"s doesn't get any work done.
>
> ?
nevermind.

>
>
>
> > -N