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Re: [gfortran] Implement irand(), rand(), and srand() for G77 compatibility

From: Paul Brook <paul at codesourcery dot com>
To: Steve Kargl <sgk at troutmask dot apl dot washington dot edu>
Cc: fortran at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
Date: Mon, 31 May 2004 00:50:41 +0100
Subject: Re: [gfortran] Implement irand(), rand(), and srand() for G77 compatibility
Organization: CodeSourcery
References: <20040530185518.GA61701@troutmask.apl.washington.edu> <200405302310.20676.paul@codesourcery.com> <20040530234527.GA63095@troutmask.apl.washington.edu>

> irand(i) returns a value in the range [1,GFC_RAND_M-1].
> irand(i) - 1 is in the range [0,GFC_RAND_M-2].  So, the
> division above is in the range [0,1).

You're forgetting that real*4 has significantly less than 32 bits precision, 
so is unable to accurately represent integers of this magnitude. After 
rounding the result will in the range [0-1]

Paul

Follow-Ups:
- Re: [gfortran] Implement irand(), rand(), and srand() for G77 compatibility
  - From: Steve Kargl

References:
- [gfortran] Implement irand(), rand(), and srand() for G77 compatibility
  - From: Steve Kargl
- Re: [gfortran] Implement irand(), rand(), and srand() for G77 compatibility
  - From: Paul Brook
- Re: [gfortran] Implement irand(), rand(), and srand() for G77 compatibility
  - From: Steve Kargl

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