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

Dmitry Nadezhin dmitry.nadezhin at gmail.com
Tue Feb 26 02:58:36 UTC 2013

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.POSITIVEINFINITY. It causes incorrect result on input like this […] It can be fixed in such a way fValue = Math.max(Float.MINVALUE, Math.min(Float.MAXVALUE, (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

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