Date: Tue, 4 Feb 2003 17:36:04 +0300 From: "Andrey A. Chernov" <ache@nagual.pp.ru> To: Dag-Erling Smorgrav <des@ofug.org> Cc: David Schultz <dschultz@uclink.Berkeley.EDU>, Kris Kennaway <kris@obsecurity.org>, current@FreeBSD.ORG Subject: Re: rand() is broken Message-ID: <20030204143604.GA93522@nagual.pp.ru> In-Reply-To: <xzpisw0unw4.fsf@flood.ping.uio.no> References: <20030204054020.GA2447@HAL9000.homeunix.com> <20030204094659.GA87303@nagual.pp.ru> <20030204115237.GA6483@HAL9000.homeunix.com> <xzpfzr4b3pw.fsf@flood.ping.uio.no> <20030204131006.GB92301@nagual.pp.ru> <20030204131748.GA92510@nagual.pp.ru> <20030204132845.GA92674@nagual.pp.ru> <20030204134714.GA92940@nagual.pp.ru> <20030204140806.GA93236@nagual.pp.ru> <xzpisw0unw4.fsf@flood.ping.uio.no>
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On Tue, Feb 04, 2003 at 15:22:03 +0100, Dag-Erling Smorgrav wrote: > > Yes we do. We get a better sequence for any given seed, i.e. we get > less correlation between n and x(n) for any given x(0). I don't think > it changes much for long sequences, but we get a better distribution > for short sequences (including short subsequences of long sequences). Maybe, I am not sure here, we need to ask expert. > As for patterns in the lower bits, we should try with a != 0 and see > how that affects the results. I believe the purpose of a in the LCG > algorithm is to scramble the lower bits. a != 0 eliminates 0 stuck problem, no additional visible effects. Even with a != 0 values are monotonically increased, I try with a == 123459876 0: 123459876 1: 185549787 2: 247639698 3: 309729609 4: 371819520 5: 433909431 6: 495999342 7: 558089253 8: 620179164 9: 682269075 -- Andrey A. Chernov http://ache.pp.ru/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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