[Patch, libfortran] PR 52434/48878/38199 Improve floating point formatted writes

[Jerry DeLisle]

On 03/15/2012 02:55 AM, Janne Blomqvist wrote:
> On Thu, Mar 15, 2012 at 01:52, Jerry DeLisle<jvdelisle@charter.net>  wrote:
>> I like the idea behind this patch.  I confess, I have not studied the two
>> test cases that you are modifying, but the changes seem to stick out with
>> too many digits there.  Is this really correct?
>> When I get another moment, I will look closer. Maybe you can explain the
>> need for this change a little more.  Sorry if I am being to careful. Its
>> been many months since I delved into the formatting code.
>
> The reason is that with the patch, the default rounding is whatever
> snprintf() gives us. At least with glibc, snprintf() rounds ties to
> even, but I'm not sure all implementations do this rather than
> rounding ties to away. So the testcase changes just make sure that
> we're not rounding a tie. E.g. "1.25" rounded to two significant
> digits is "1.2" if one rounds ties to even, "1.3" if ties are rounded
> away. So using "1.250001" ensures that the rounded value is "1.3" with
> both rounding modes.
>
> I suppose another option would be to assume that rounding is ties to
> even, and keep an eye out for regressions on other targets.
>
>

Understood, thanks.  patch OK for trunk.


Jerry