[ python-Bugs-1472695 ] 32/64bit pickled Random incompatiblity

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Bugs item #1472695, was opened at 2006-04-19 01:10
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Category: Python Library
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Peter Maxwell (pm67nz)
Assigned to: Nobody/Anonymous (nobody)
Summary: 32/64bit pickled Random incompatiblity

Initial Comment:
The unsigned long integers which make up the state of a Random 
instance are converted to Python integers via a cast to long in 
_randommodule.c's random_getstate function, so on a 32bit platform 
Random.getstate() returns a mix of postitive and negative integers, while 
on a 64bit platform the negative numbers are replaced by larger positive 
numbers, their 32bit-2s-complement equivalents.

As a result, unpicking a Random instance from a 64bit machine on a 32bit 
platform produces the error "OverflowError: long int too large to convert 
to int".  Unpickling a 32bit Random on a 64bit machine succeeds, but the 
resulting object is in a slightly confused state:

>>> r32 = cPickle.load(open('r32_3.pickle'))
>>> for i in range(3):
...     print r64.random(), r32.random()
... 
0.237964627092 4292886520.32
0.544229225296 0.544229225296
0.369955166548 4292886520.19



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