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Re: Octave 3.0.1 available for ftp


From: Tatsuro MATSUOKA
Subject: Re: Octave 3.0.1 available for ftp
Date: Fri, 25 Apr 2008 03:29:58 +0900 (JST)

Hello

Thank you John

I'll report the problem to MinGW ML.

Regards

Tatsuro



--- "John W. Eaton" <address@hidden> wrote:

> On 24-Apr-2008, Michael Goffioul wrote:
> 
> | On Thu, Apr 24, 2008 at 3:38 PM, Tatsuro MATSUOKA <address@hidden> wrote:
> | > Hello David
> | >
> | >  Thank you for your reply.
> | >
> | >  --- David Bateman <address@hidden> wrote:
> | >  > Wouldn't it better better to have the autoconf test refuse to set
> | >  > HAVE_ROUND for mingw rather than hard code in the source.. 
> Alternatively
> | >  > we code test the behavior of the round function in an autoconf test to
> | >  > see if it fails for the case near bitmax, though that would be more 
> work
> | >  > to implement..
> | >  >
> | >  > D.
> | >
> | >  What you said is right.  However, I do not have enough knowledge of auto 
> tools.
> | >  And I cannot understand what is the problem with 'round' implemeted in 
> the MinGW g++ 3.4.5.
> | >  If you suggest me a autoconf modification, I will test to it and report 
> here.
> | 
> | The code used internally by MinGW for "round" is the following
> | (http://www.koders.com/c/fidB63EAFA2C117AAFC1CF9FE9691F8DDBE4DD01A22.aspx)
> | 
> | double
> | round (double x)
> | {
> |   /* Add +/- 0.5 then then round towards zero.  */
> |   return trunc ( x + (x >= 0.0 ?  0.5 : -0.5));
> | }
> | 
> | The problem with this implementation is when x is the vicinity of bitmax: it
> | leads to floating-point overflow (in the mantissa) and produces rounding 
> error,
> | For instance if x = bitmax, round(x) => bitmax+1, while it should return
> | bitmax.
> | 
> | Octave used to use the above implementation for MSVC, but because of
> | this problem, I switched it to use the (more robust) gnulib implementation.
> 
> Please report the problem to the MinGW maintainers.  In the meantime,
> it would be helpful to have a configure test that actually tests the
> feature, not just that we are running on a MinGW system.  That way,
> the test should automatically switch to using code from MinGW when the
> problem is fixed in their sources.
> 
> Thanks,
> 
> jwe
> 


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