[PATCH] Sunbug 7131192: Optimize BigInteger.doubleValue(), floatValue()

[Dmitry Nadezhin]

Hi Brian,

The reported benchmark results are impressive:
http://bugs.sun.com/view_bug.do?bug_id=7032154

Where can we find the 7032154 patch to review it ?

  Dima

On Tue, Feb 26, 2013 at 12:50 AM, Brian Burkhalter
<brian.burkhalter at oracle.com> wrote:
> Hi Dima,
>
> On Feb 25, 2013, at 1:14 AM, Dmitry Nadezhin wrote:
>
> I looked at your fix of sunbug=6358355  "Fix Float.parseFloat to round
> correctly and preserve monotonicity".
> […]
>
> 1) The line in floatValue() method
> fValue = (float) doubleValue();
>
> fValue can become Float.POSITIVE_INFINITY.
> It causes incorrect result on input like this
> […]
>
> It can be fixed in such a way
> fValue = Math.max(Float.MIN_VALUE, Math.min(Float.MAX_VALUE, (float)
> doubleValue()));
>
>
> Thanks for the catch!
>
> 2)  The line in floatValue() method.
> // difference is exactly half an ULP
> // round to some other value maybe, then finish
> fValue += 0.5f*ulp( fValue, overvalue );
>
> When fValue is subnormal, the right-hand sign evaluates to 0, fValue
> remains unchanged.
> This is similar to the bug 4396272 - Parsing doubles fails to follow
> IEEE for largest decimal that should yield 0.
> […]
>
>
> It can be fixed in such a way
> fValue = (float) (fValue + 0.5*ulp(fValue, overvalue));
> Constant 0.5 instead of 0.5f causes double evaluation of right-hand
> side, so it doesn'nt underflow.
>
>
> I was intending to comment on this as well.
>
> Once approved, I was thinking that the patch for 7192954 "Fix
> Float.parseFloat to round correctly and preserve monotonicity" should be
> applied first followed by patches for 4396272 "Parsing doubles fails to
> follow IEEE for largest decimal that should yield 0" and
> "BigInteger.doubleValue() is depressingly slow." I initiated some of these
> reviews out of this sequence as I had not become aware of all the linkages.
>
> I am actually also wondering whether the patch for 7032154 "Performance
> tuning of sun.misc.FloatingDecimal/FormattedFloatingDecimal," which I just
> learned of today, should perhaps be dealt with prior to any of the above?
>
> Thanks,
>
> Brian