DigitList bug in recent patch

[Brian Burkhalter]

Interesting. This week I was just running some regression tests against the updated patch for 7032154 (not yet posted) and the only failures I found were in the HALF_* cases in TieRoundingTest.

I'll check out what you reported while looking into it.

Thanks,

Brian

On Mar 27, 2013, at 12:50 AM, Frank Ding wrote:

> Current JDK gives the output of "78.0001".
> 
> Best regards,
> Frank
> 
> On 3/27/2013 3:48 PM, Frank Ding wrote:
>> Hi guys,
>>  We noticed there is a recent change (patch @ http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/bc1f16f5566f ) that changed the behavior of the following program.
>> 
>> import java.math.RoundingMode;
>> public class TestNumberFormat {
>> 
>>    public static void main(String[] args) {
>> 
>>        java.text.NumberFormat numberFormat = java.text.NumberFormat.getInstance(
>>                java.util.Locale.US);
>>        double v = 78.00005;
>>        numberFormat.setMaximumFractionDigits(4);
>>        numberFormat.setRoundingMode(RoundingMode.HALF_EVEN);
>>        numberFormat.setMinimumFractionDigits(0);
>>        numberFormat.setGroupingUsed(false);
>>        String ret = numberFormat.format(v);
>>        System.out.println(ret);
>>    }
>> }
>> 
>> Note the rounding mode HALF_EVEN and the expected output should be "78" which can also be verified by running previous jdk (before b73).
>> 
>> Stepping into code and the suspicious code is in DigitList.shouldRoundUp().  allDecimalDigits is false so true is returned, causing the last digit in fraction part to be 1.
>>            case HALF_EVEN:
>>                // Implement IEEE half-even rounding
>>                if (digits[maximumDigits] > '5') {
>>                    return true;
>>                } else if (digits[maximumDigits] == '5' ) {
>>                    if (maximumDigits == (count - 1)) {
>>                        // the rounding position is exactly the last index :
>>                        if (alreadyRounded)
>>                            // If FloatingDecimal rounded up (value was below tie),
>>                            // then we should not round up again.
>>                            return false;
>> 
>>                        if (!allDecimalDigits)
>>                            // Otherwise if the digits dont represent exact value,
>>                            // value was above tie and FloatingDecimal truncated
>>                            // digits to tie. We must round up.
>>                            return true;
>> 
>> Since I am not familiar of the numeric conversion, can any one shed your light on it?
>> 
>> Best regards,
>> Frank
>