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Topic: RNGs: A Super KISS
Replies: 14   Last Post: Feb 26, 2013 10:53 AM

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adrian dogsbody

Posts: 110
Registered: 12/13/04
Re: RNGs: A Super KISS
Posted: Nov 3, 2009 7:38 PM
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"Tom St Denis" <tom@iahu.ca> ha scritto nel messaggio
news:4fd3c8bf-e45b-4359-ac50-f54298b14770@d21g2000yqn.googlegroups.com...
On Nov 3, 10:46 am, geo <gmarsag...@gmail.com> wrote:
> int refill( )
> { int i; unsigned long long t;
> for(i=0;i<41790;i++) { t=7010176LL*Q[i]+carry; carry=(t>>32); Q[i]=~
> (t);}
> indx=1; return (Q[0]);
> }


Not to nitpick but your C code could use some work. First off, some
indentation please? Second, returning a unsigned long long as "int"
is not very portable.

<where is written that he return long long int like int??
<Q is "static unsigned long Q[41790]"
<he return only "unsigned long" like "int"
<the error could be here "Q[i]=~(t)" because in the left side is long
<the other side is long long

Part of the good thing of PRNGs is that they're reproduceable.
Ideally over different platforms. You should truncate the return
value if you want it as "int" or change the return type. As it stands
now this will produce different results on my x86-32 and 64 boxes for
the same seed, which is a bad thing.

Tom






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