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Re: Octave 3.0.1 available for ftp
From: |
John W. Eaton |
Subject: |
Re: Octave 3.0.1 available for ftp |
Date: |
Thu, 24 Apr 2008 13:36:23 -0400 |
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
- Re: Octave 3.0.1 available for ftp, (continued)
- Re: Octave 3.0.1 available for ftp, Michael Goffioul, 2008/04/22
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/22
- Re: Octave 3.0.1 available for ftp, Michael Goffioul, 2008/04/22
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/22
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/24
- Re: Octave 3.0.1 available for ftp, Michael Goffioul, 2008/04/24
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/24
- Re: Octave 3.0.1 available for ftp, David Bateman, 2008/04/24
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/24
- Re: Octave 3.0.1 available for ftp, Michael Goffioul, 2008/04/24
- Re: Octave 3.0.1 available for ftp,
John W. Eaton <=
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/24
- about 'round' function on mingw, Tatsuro MATSUOKA, 2008/04/24
- Re: about 'round' function on mingw, Tatsuro MATSUOKA, 2008/04/24
- Re: about 'round' function on mingw, John W. Eaton, 2008/04/24
- Re: about 'round' function on mingw, Tatsuro MATSUOKA, 2008/04/24
- Re: about 'round' function on mingw, Sergei Steshenko, 2008/04/24
- Re: about 'round' function on mingw, Tatsuro MATSUOKA, 2008/04/24
- Re: Octave 3.0.1 available for ftp, John W. Eaton, 2008/04/24
- Re: Octave 3.0.1 available for ftp, Tatsuro MATSUOKA, 2008/04/25
- Re: Octave 3.0.1 available for ftp, Michael Goffioul, 2008/04/25