From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
Message-Id: <200007121642.SAA23906@father.ludd.luth.se>
Subject: Quicker erand48 patch
To: djgpp-workers AT delorie DOT com (DJGPP-WORKERS)
Date: Wed, 12 Jul 2000 18:42:03 +0200 (MET DST)
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Reply-To: djgpp-workers AT delorie DOT com

FYI, I've implemented a faster erand48 from the suggestions from Dieter.


Right,

							MartinS

Patch (pasted):
? src/libc/compat/stdlib/.rand48.safe
Index: src/libc/compat/stdlib/rand48.c
===================================================================
RCS file: /cvs/djgpp/djgpp/src/libc/compat/stdlib/rand48.c,v
retrieving revision 1.1
diff -r1.1 rand48.c
4c4
<  * Copyright (C) 1999 Martin Str<94>mberg <ams AT ludd DOT luth DOT se>.
---
>  * Copyright (C) 1999, 2000 Martin Str@"omberg <ams AT ludd DOT luth DOT se>.
57,59c57,58
<   int i; /* Counter. */
<   double pot = 0.5; /* A potential of 0.5. */
<   double result = 0.0;
---
>   /* Thanks to Dieter Buerssner for showing how it ought to be done. */
>   signed long long ll; /* Temporary result holder. */
63,80c62,64
<   for(i = 0; i < 8*sizeof(unsigned short); i++)
<   {
<     if( (state[2] << i) & 0x8000 )
<     {
<       result += pot;
<     }
<     pot /= 2.0;
<     if( (state[1] << i) & 0x8000 )
<     {
<       result += pot;
<     }
<     pot /= 2.0;
<     if( (state[0] << i) & 0x8000 )
<     {
<       result += pot;
<     }
<     pot /= 2.0;
<   }
---
>   ll = (signed long long)( state[0]
>                      | ( (unsigned long)state[1] ) << 16
>                      | ( (unsigned long long)state[2] ) << 32 );
82c66
<   return(result);
---
>   return(ll * ( 1.0 / ( 1LL << 48 ) ) );