KISS4691, a potentially top-ranked RNG.
in [Math]
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From: Richard Maine on 11 Aug 2010 00:36 Dann Corbit <dcorbit(a)connx.com> wrote: > In article <i3ssd1$be8$1(a)speranza.aioe.org>, > g.bogle(a)auckland.no.spam.ac.nz says... > > You do realize that there's no unsigned integer type in Fortran? .... > Maybe he is using Sun's Fortran 95 compiler. Though if my admittedly fallible memory serves me, the unsigned integer in Sun's f95 has restrictions that are likely to surprise many casual users. Being more specific might stretch my memory a bit farther than I trust, but I think I recall a lack of mixed-mode operations, for example. So one would have to tread pretty carefully in order to correctly transcribe pseudocode into working code. For example, I'm not at all sure that one can do such things as adding 1 to an unsigned integer; I think you might have to add 1U instead. -- Richard Maine | Good judgment comes from experience; email: last name at domain . net | experience comes from bad judgment. domain: summertriangle | -- Mark Twain
From: glen herrmannsfeldt on 11 Aug 2010 00:47 In comp.lang.fortran orz <cdhorz(a)gmail.com> wrote: (snip) > 3. Shift operators are treated as higher precedence or parentheses > are added around that shift. The C precedence rules for shifts are widely believed to be wrong, including by the developers of C, but it is considered too late to change. Best to always use parentheses around them. (Many Fortran rules haven't been changed for the same reason.) -- glen
From: robin on 12 Aug 2010 09:49
"Gib Bogle" <g.bogle(a)auckland.no.spam.ac.nz> wrote in message news:i3ssd1$be8$1(a)speranza.aioe.org... | orz wrote: | | > If I made yet another mistake on that then I'm going to throw | > something. | > | > It produced identical results for me when I tried it in C using this | > code: | > | > typedef unsigned int Uint32; | > Uint32 sign(Uint32 value) {return value>>31;} | > Uint32 index, carry, data[4691]; | > Uint32 mwc4691() { | > index = (index < 4690) ? index + 1 : 0; | > Uint32 x = data[index]; | > Uint32 t = (x << 13) + carry + x; | > if (sign((x<<13)+carry) == sign(x)) | > carry = sign(x) + (x>>19); | > else carry = 1 - sign(t) + (x>>19); | > data[index] = t; | > return t; | > } | > | > I think the only difference between that and the algorithm he | > expressed in pseudocode is that I added parentheses on the first left- | > shift (he was apparently assuming higher precedence on the leftshift | > operator than C uses). Maybe that's why you're getting different | > results? | | You do realize that there's no unsigned integer type in Fortran? I don't think | there's much point in trying to predict what the Fortran code does without using | a Fortran compiler. It's perfectly possible to predict how to program the operation (unsigned arithmetic) in Fortran provided that we make the assumption that the hardware provides twos complement arithmetic. |