Java 8 RFR 8010430: Math.round has surprising behavior for odd values of ulp 1

[Brian Burkhalter]

With respect to this issue, the argument satisfies the condition

a == (int)a

or

a == (long)a

so there really is no tie, unless I am missing something. The problem is that in the current implementation the intermediate result

a + 0.5

is rounded according to the IEEE standard so the conditions above are no longer true.

On Aug 23, 2013, at 1:24 PM, Dmitry Nadezhin wrote:

> The specification of java.lang.Math.round() says
>    * Returns the closest {@code int} to the argument, with ties
>     * rounding up.
> 
> It is not clarified what is "ties rounding up".
> I guess that it should correspond to the direction "roundTiesToAway" of
> IEEE 754-2008
> and to the java.math.RoundingMode.HALF_UP .
> 
> They round
> +0.5 -> +1
> -0.5 -> -1
> 
> The current implementation of java.lang.Math.round() rounds
> +0.5 -> +1
> -0.5 -> 0
> 
> "ties rounding up" should match IEEE754 standard and other JDK math class,
> shouldn't it ?