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* Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat (fwd)
@ 2003-03-21 15:06 Wolfgang Bangerth
0 siblings, 0 replies; only message in thread
From: Wolfgang Bangerth @ 2003-03-21 15:06 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR c/10176; it has been noted by GNATS.
From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
To: gcc-gnats@gcc.gnu.org
Cc:
Subject: Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat
(fwd)
Date: Fri, 21 Mar 2003 09:03:47 -0600 (CST)
---------- Forwarded message ----------
Date: 20 Mar 2003 18:49:53 -0800
From: Ernst Berg <ernstberg@bigvalley.net>
To: bangerth@dealii.org
Subject: Re: c/10176: Broken nested Do loop: simple example. gcc 3.2 redhat
It would need to look for a power of 3.. I was looking at the parity
language of it.
I just ran it again to get an example and it worked. I don't get it.
I am sorry.. I'm not sure why it wouldn't work before even after I
powered off and rebooted..
False alarm.
This is a related function to the Collatz problem 3x+1 if( odd )
-----
2 if ( even )
On Thu, 2003-03-20 at 17:51, bangerth@dealii.org wrote:
> Synopsis: Broken nested Do loop: simple example. gcc 3.2 redhat
>
> State-Changed-From-To: open->feedback
> State-Changed-By: bangerth
> State-Changed-When: Fri Mar 21 01:51:28 2003
> State-Changed-Why:
> Your program 4x.c is essentially equivalent to this one:
> --------------------------
> int main(void)
> {
> unsigned int count = 1;
> do {
> if( count % 3 ) { count *= 4; count += 2; }
> else { count /= 3; }
>
> if( count == 1 ) break;
> if( count == 3 ) break;
> } while(1);
> return(0);
> }
> ----------------------
> What happens is that you never jump out of the inner loop.
> Unfortunately, I don't see right away why the loop should
> terminate at all. gcc seems to have the same problem, as
> does icc. Can you give a simple argument why it should?
>
> Thanks
> Wolfgang
>
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10176
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