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| Date | Sun, 07 Jun 2015 12:41:53 +0200 |
| From | Jonas Wielicki <jonas@wielicki.name> |
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| Subject | Re: Testing random |
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On 07.06.2015 08:27, Cecil Westerhof wrote:
> I wrote a very simple function to test random:
> def test_random(length, multiplier = 10000):
> number_list = length * [0]
> for i in range(length * multiplier):
> number_list[random.randint(0, length - 1)] += 1
> minimum = min(number_list)
> maximum = max(number_list)
> return (minimum, maximum, minimum / maximum)
>
> When running:
> for i in range(1, 7):
> print(test_random(100, 10 ** i))
> I get:
> (3, 17, 0.17647058823529413)
> (73, 127, 0.5748031496062992)
> (915, 1086, 0.8425414364640884)
> (9723, 10195, 0.9537027954879843)
> (99348, 100620, 0.9873583780560524)
> (997198, 1002496, 0.9947151908835546)
>
> and when running:
> for i in range(1, 7):
> print(test_random(1000, 10 ** i))
> I get:
> (2, 20, 0.1)
> (69, 138, 0.5)
> (908, 1098, 0.8269581056466302)
> (9684, 10268, 0.9431242695753799)
> (99046, 100979, 0.9808574059953059)
> (996923, 1003598, 0.9933489305478886)
>
> It shows that when the first parameter increases the deviation
> increases and when the second parameter increases the deviation
> decreases. Exactly what you would expect. But what are the ranges you
> would expect with a good random function.
Really depends on the number of samples. Appearantly, a good RNG would
come close to 1.0 for the ratio.
> Then it could be used to test a random function.
This is an interesting test (more interesting to me than it looks at the
first sight, and certainly better than what I had come up with), but
unfortunately, there is more to testing randomness.
The test clearly suggests that random functions should have a min/max
ratio of about 1.0. Think of a "random" function like this:
def fake_random(minv, maxv, _cache={}):
try:
return next(_cache[minv, maxv])
except (StopIteration, KeyError):
iterator = iter(range(minv, maxv+1))
_cache[minv, maxv] = iterator
return next(iterator)
(if that is hard to read, I agree; it returns the sequence from minv to
maxv (inclusively) over and over again for equal minv and maxv. don’t
pass anything to _cache :), just call it like random.randint)
This gives a "perfect" ratio of 1.0, but is not very random. This kind
of function would probably be ruled out by a compression or correlation
test. If you want to dig deeper into the algorithms for random testing,
the dieharder test suite [1] is probably worth a look.
It all boils down to the use case. For some use cases, the
``fake_random`` might be good enough (unittesting would be such a case:
it is certainly uniformly distributed and allows full coverage of the
tested range), for others it would fail catastrophically (don’t generate
your cryptographic keys with this!).
cheers,
Jonas
[1]: http://www.phy.duke.edu/~rgb/General/dieharder.php
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Testing random Cecil Westerhof <Cecil@decebal.nl> - 2015-06-07 08:27 +0200
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 12:40 +0200
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-07 21:51 +1000
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 17:51 +0200
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 02:25 +1000
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 18:36 +0200
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 02:44 +1000
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 20:23 +0200
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 04:52 +1000
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 21:41 +0200
Re: Testing random Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-06-07 22:08 +0300
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 21:29 +0200
Re: Testing random random832@fastmail.us - 2015-06-07 15:44 -0400
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 22:09 +0200
Re: Testing random random832@fastmail.us - 2015-06-07 16:41 -0400
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 22:59 +0200
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-08 11:26 +1000
Re: Testing random random832@fastmail.us - 2015-06-07 21:34 -0400
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 11:42 +1000
Re: Testing random MRAB <python@mrabarnett.plus.com> - 2015-06-08 02:49 +0100
Re: Testing random random832@fastmail.us - 2015-06-07 21:57 -0400
Re: Testing random Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-06-08 10:40 +0300
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-10 19:03 +0200
Re: Testing random sohcahtoa82@gmail.com - 2015-06-10 10:52 -0700
Re: Testing random Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-06-10 23:00 +0300
Re: Testing random Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-10 12:02 -0600
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-12 23:32 +0200
Re: Testing random alister <alister.nospam.ware@ntlworld.com> - 2015-06-12 21:46 +0000
Re: Testing random random832@fastmail.us - 2015-06-12 17:52 -0400
Re: Testing random Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-12 16:00 -0600
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-13 00:09 +0200
Re: Testing random sohcahtoa82@gmail.com - 2015-06-12 15:55 -0700
Re: Testing random random832@fastmail.us - 2015-06-12 18:57 -0400
Re: Testing random Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-13 08:53 +0100
Re: Testing random random832@fastmail.us - 2015-06-10 14:26 -0400
Re: Testing random Ned Batchelder <ned@nedbatchelder.com> - 2015-06-07 14:21 -0700
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-16 21:18 +0200
Re: Testing random random832@fastmail.us - 2015-06-16 16:23 -0400
Re: Testing random Ned Batchelder <ned@nedbatchelder.com> - 2015-06-16 13:48 -0700
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-16 23:57 +0200
Re: Testing random sohcahtoa82@gmail.com - 2015-06-16 15:30 -0700
Re: Testing random Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-16 16:58 -0600
Re: Testing random Laura Creighton <lac@openend.se> - 2015-06-17 11:28 +0200
Re: Testing random Ned Batchelder <ned@nedbatchelder.com> - 2015-06-16 16:26 -0700
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-17 01:45 +0200
Re: Testing random sohcahtoa82@gmail.com - 2015-06-16 17:36 -0700
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-17 11:01 +1000
Re: Testing random Ethan Furman <ethan@stoneleaf.us> - 2015-06-16 18:32 -0700
Re: Testing random Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-17 09:41 +0100
Re: Testing random Grant Edwards <invalid@invalid.invalid> - 2015-06-17 14:04 +0000
Re: Testing random Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-17 09:01 -0600
Re: Testing random MRAB <python@mrabarnett.plus.com> - 2015-06-17 01:42 +0100
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-17 08:53 +0200
Re: Testing random Christian Gollwitzer <auriocus@gmx.de> - 2015-06-17 09:22 +0200
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-17 17:28 +1000
Re: Testing random Tim Golden <mail@timgolden.me.uk> - 2015-06-17 08:30 +0100
Re: Testing random Cecil Westerhof <Cecil@decebal.nl> - 2015-06-17 11:57 +0200
Re: Testing random Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-17 01:36 +0000
Re: Testing random Laura Creighton <lac@openend.se> - 2015-06-17 12:33 +0200
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-17 22:47 +1000
Re: Testing random Laura Creighton <lac@openend.se> - 2015-06-17 15:50 +0200
Re: Testing random Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-17 01:35 +0000
Re: Testing random Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2015-06-17 07:41 +0300
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-08 11:11 +1000
Re: Testing random Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-07 11:07 -0600
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 03:20 +1000
Re: Testing random "C.D. Reimer" <chris@cdreimer.com> - 2015-06-07 10:36 -0700
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-08 04:28 +1000
Re: Testing random Chris Angelico <rosuav@gmail.com> - 2015-06-08 04:40 +1000
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-08 04:24 +1000
Re: Testing random Jonas Wielicki <jonas@wielicki.name> - 2015-06-07 12:41 +0200
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-07 22:52 +1000
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-07 23:06 +1000
Re: Testing random Peter Otten <__peter__@web.de> - 2015-06-07 15:35 +0200
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 18:36 +0200
Re: Testing random Peter Otten <__peter__@web.de> - 2015-06-07 18:48 +0200
Re: Testing random Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-07 22:15 +0200
Re: Testing random Steven D'Aprano <steve@pearwood.info> - 2015-06-08 11:35 +1000
Re: Testing random Christian Gollwitzer <auriocus@gmx.de> - 2015-06-07 14:53 +0200
Re: Testing random Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-06-07 11:04 -0400
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