| Re: Randomu() behavior - BAD! [message #68595] |
Fri, 13 November 2009 13:42 |
Conor
Messages: 138
Registered: February 2007
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Senior Member |
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On Nov 13, 3:43 pm, David Fanning <n...@dfanning.com> wrote:
> Conor writes:
>> So I did a simple test and have a better idea of how the seed
>> initialization works with randomu(). In my mind, this is not good
>> news!
>
> I've written a new RandomNumberGenerator object this morning
> that may get around some of these problems. (And avoid
> common blocks, too!) You can find it here:
>
> http://www.dfanning.com/programs/randomnumbergenerator__defi ne.pro
>
> There are probably any number of way you could use
> this object, but here is one possibility. You could
> create a new system variable that would be able to give
> you random numbers on demand. The seed is always maintained
> properly, so that the random number sequence will not repeat
> in your lifetime. ;-)
>
> IDL> DefSysV, !RNG, Obj_New('RandomNumberGenerator')
> IDL> Print, !RNG -> GetRandomNumbers(3)
> 0.089239137 0.77428782 0.069180504
>
> You can set the initial seed, but if you don't, the number
> of seconds after 1 January 1970 is used. The random sequence
> will continue for as long as the object is alive in the IDL
> session.
>
> You could create this object and system variable, for example,
> in your IDL startup script, and then any program you wrote
> could access it.
>
> Cheers,
>
> David
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
Oooh, I like it!
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| Re: Randomu() behavior - BAD! [message #68597 is a reply to message #68595] |
Fri, 13 November 2009 12:43  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Conor writes:
> So I did a simple test and have a better idea of how the seed
> initialization works with randomu(). In my mind, this is not good
> news!
I've written a new RandomNumberGenerator object this morning
that may get around some of these problems. (And avoid
common blocks, too!) You can find it here:
http://www.dfanning.com/programs/randomnumbergenerator__defi ne.pro
There are probably any number of way you could use
this object, but here is one possibility. You could
create a new system variable that would be able to give
you random numbers on demand. The seed is always maintained
properly, so that the random number sequence will not repeat
in your lifetime. ;-)
IDL> DefSysV, !RNG, Obj_New('RandomNumberGenerator')
IDL> Print, !RNG -> GetRandomNumbers(3)
0.089239137 0.77428782 0.069180504
You can set the initial seed, but if you don't, the number
of seconds after 1 January 1970 is used. The random sequence
will continue for as long as the object is alive in the IDL
session.
You could create this object and system variable, for example,
in your IDL startup script, and then any program you wrote
could access it.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: Randomu() behavior - BAD! [message #68599 is a reply to message #68597] |
Fri, 13 November 2009 12:11 |
Jean H.
Messages: 472
Registered: July 2006
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Senior Member |
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David Fanning wrote:
> Conor writes:
>
>> So I did a simple test and have a better idea of how the seed
>> initialization works with randomu().
>
> Most interesting. What version of IDL are you using, Conor?
>
> Cheers,
>
> David
Same behavior here:
{ x86_64 Win32 Windows Microsoft Windows 7.0.8 Feb 9 2009 64 64}
Jean
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| Re: Randomu() behavior - BAD! [message #68600 is a reply to message #68599] |
Fri, 13 November 2009 12:10 |
Conor
Messages: 138
Registered: February 2007
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Senior Member |
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On Nov 13, 2:26 pm, David Fanning <n...@dfanning.com> wrote:
> Conor writes:
>> So I did a simple test and have a better idea of how the seed
>> initialization works with randomu().
>
> Most interesting. What version of IDL are you using, Conor?
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")
IDL Version 6.4 (linux x86 m32). (c) 2007, ITT Visual Information
Solutions
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| Re: Randomu() behavior - BAD! [message #68603 is a reply to message #68600] |
Fri, 13 November 2009 11:26 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Conor writes:
> So I did a simple test and have a better idea of how the seed
> initialization works with randomu().
Most interesting. What version of IDL are you using, Conor?
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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