Random number in Fortran 90/95
in [Fortran]
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From: GaryScott on 28 Jun 2010 18:45 On Jun 28, 5:28 pm, glen herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote: > Jason Riedy <ja...(a)acm.org> wrote: > > (snip) > > > Here's one for you, which I cannot find but expect is not specified: Do > > you happen to know if the statistical interplay between random numbers > > and images are specified? I haven't found anything, and I suspect the > > issue was either ignored or so contentious that it wasn't included. > > (from Fortran 2003) > > "Returns one pseudorandom number or an array of pseudorandom > numbers from the uniform distribution over the range 0 x < 1." > snip My only issue would be that it should have been more accurately named such as pseudorandom or PRAND. I would like a "truly" (or whatever the best you can get is) random sequence generator. > -- glen
From: Dan Nagle on 28 Jun 2010 18:47 Hello, On 2010-06-28 18:21:07 -0400, nospam(a)see.signature (Richard Maine) said: > > My off-hand guess is that nobody even thought about it, but that's not > based on any real data. It is just the kind of thing I'd have expected > to get overlooked. There was a proposal for adding a STREAM= to the rng stuff. It wasn't done because there was too much to do compared with the number of folks to do things. I'm not sure whether there was a consensus on the design, but that's another matter. It would likely have been close to what UPC does, if that was at all agreeable to the committee. It may still make it into the "More Coarrays" TR that will come along in a year or so. -- Cheers! Dan Nagle
From: glen herrmannsfeldt on 28 Jun 2010 19:00 GaryScott <garylscott(a)sbcglobal.net> wrote: (snip on RANDOM_NUMBER) > snip > My only issue would be that it should have been more accurately named > such as pseudorandom or PRAND. I would like a "truly" (or whatever > the best you can get is) random sequence generator. Some years ago Intel had a hardware random number generator based on a noise source and logic to remove any bias that otherwise would appear. I believe it was in a support chip for one of the Pentium families, not in the processor itself. In any case, it seems to have been forgotten by now. I would guess that the standard wouldn't require a hardware generator, as not all systems would be able to support it. It seems, though, that since the standard specifies pseudo-random that a hardware noise source generator couldn't be used. -- glen
From: Richard Maine on 28 Jun 2010 19:19 GaryScott <garylscott(a)sbcglobal.net> wrote: > I would like a "truly" (or whatever > the best you can get is) random sequence generator. That would be a bit out of line for a software standard. The question of what "truly random" means is perhaps as much philosophical as anything, but most definitions would rule out anything implemented purely in software. If it is generated purely by software, then is is pseudorandom, pretty much by definition. Sounds to me like you are talking about a spec for a hardware peripheral. Don't hold your breath for anything even vaguely close in the Fortran standard. I can't interpret your "or whatever the best you can get is". Maybe that means you aren't really talking about a hardware peripheral, but instead are asking for a "good quality" pseudorandom generator, that being all you can do in software. But as to exactly what the "best" one would be...If you want the Fortran standard to specify that the best one be used, you'd first have to get agreement on exactly what would define such a "best" one. Methinks you are in the wrong group for that (and that you aren't going to get agreement on a definitive answer anytime soon.) -- Richard Maine | Good judgment comes from experience; email: last name at domain . net | experience comes from bad judgment. domain: summertriangle | -- Mark Twain
From: Phillip Helbig---undress to reply on 29 Jun 2010 01:22
In article <1jksya9.5pgpx31gjknhqN%nospam(a)see.signature>, nospam(a)see.signature (Richard Maine) writes: > I haven't been directly involved with much after f2003, and in > particular, with the coarray stuff. (In fact, until I saw your later > mention of coarrays, I didn't pick up what you were talking about when > you said "images". Nothing wrong with your usage; I just haven't been > imersed in it enough that the term makes coarray stuff imediately pop > into my mind. My initial reaction was to wonder why anyone thought the > Fortran standard would say anything about picture images.) I was thinking of executables. |