From chemistry-request@server.ccl.net Wed Oct 2 03:38:23 2002 Received: from mailgate.rz.uni-karlsruhe.de (exim@[129.13.64.97]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id g927cNc03069 for ; Wed, 2 Oct 2002 03:38:23 -0400 Received: from rz70.rz.uni-karlsruhe.de (rz70.rz.uni-karlsruhe.de [129.13.97.243]) by mailgate.rz.uni-karlsruhe.de with esmtp (Exim 3.36 #1) id 17we56-0000VR-00; Wed, 02 Oct 2002 09:38:04 +0200 Date: Wed, 2 Oct 2002 09:38:04 +0200 (CES) From: Harald Svedung To: sweta nigam cc: chemistry@ccl.net, Subject: Re: CCL:random no.generation(doubt) In-Reply-To: <003701c2687a$e8382e50$a62813ac@ATCSWETANIGAM> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from QUOTED-PRINTABLE to 8bit by server.ccl.net id g927cNc03070 hello, A random number generator with very little remaining structure in the result of consecutive calls may look like this: function ggubs() cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c ggubs c c c purpose - basic uniform (0,1) pseudo-random number c generator c arguments dseed - input/output double precision variable c assigned an integer value in the c exclusive range (1.d0, 2147483647.d0). c dseed is replaced by a new value to be c used in a subsequent call. c c real*8 dseed,c1,c2,ggubs,c3 include 'mpif.h' parameter (c1=2147483647.d+00,c2=2.d+00**(-31),ic3=16807) common/random/dseed dseed=dmod(ic3*dseed,c1) ggubs=c2*dseed i=i+1 5 format(d30.20) return end where dmod(x,y) does the following: DMOD DMOD calculates a longreal number modulus a second longreal number. Declaration FUNCTION DMOD(VAR x,y:LONGREAL):LONGREAL; EXTERNAL; Attributes Parameters: Both arguments are longreal numbers. Result: A longreal number. HP FORTRAN 77/XL: Intrinsic function: Z=DMOD(X,Y). Error: If either of the arguments is a NaN (or the first argument is infinity or the second argument is zero), there are two possible actions. If the INVALID trap is enabled, the message "DMOD(X,Y): ANY OF X AND Y=NaN OR X=INFINITY OR Y=0.0" occurs. Otherwise, the INVALID flag is set. In either case, a quiet NaN is returned. This was tested in the context of phase space sampling for molecular dynamics simulations by some folks in Göteborg like 10 years ago (I havn't got the exact reference at arms length, sorry) and it has been used ever since. for what it's worth ;-) /Harald On Mon, 30 Sep 2002, sweta nigam wrote: > hello > can u help me to find out what r random no.generators ,plz site some examples used in commercial software like tripos or accelrys in their molecular dyanamics suite... > > Thanks n Regards > Sweta > TCS > Dr. Harald Svedung cellphone: +49-175 736 2576 Institut für Physikalische Chemie or: +46-709-223 206 Universität Karlsruhe Fritz-Haber-Weg 4 D-761 28 Karlsruhe Tyskland Tel: +49-721 608 2715 Fax:+49-721 608 6524