RFR [9]: 8050142: Optimize java.util.Formatter

[Andrej Golovnin]

Hi Claes,

it looks good. And I have one minor improvement. Take look at the following
lines of the method FormatSpecifier#hexDouble(double, int):

3532                             // Get exponent and append at the end.
3533                             String exp = res.substring(idx + 1);
3534                             int iexp = Integer.parseInt(exp) -54;
3535                             return res.substring(0, idx) + "p"
3536                                 + Integer.toString(iexp);

The lines 3535-3536 are translated by the compiler to:

new StringBuilder().append(res.substring(0,
idx)).append("p").append(Integer.toString(iexp)).toString();

If we rewrite it to use StringBuilder, we can avoid creation of
intermediate String objects, e.g.:

3535                             return new StringBuilder().append(res, 0,
idx).append('p')
3536                                 .append(iexp).toString();

But I'm not sure how common is the usage of #hexDouble-method. Maybe this
change is not worth it.

Best regards,
Andrej Golovnin



On Mon, Jul 14, 2014 at 2:23 PM, Claes Redestad <claes.redestad at oracle.com>
wrote:

> Hi again,
>
>  updated webrev: http://cr.openjdk.java.net/~redestad/8050142/webrev.1
>
>  changes:
>  - specify capacity on line 2931 as suggested by Andrej Golovnin
>  - exp.append("0") -> exp.append('0') on line 3781
>  - merged append+justify into appendJustified as suggested by Peter Levart
>  - replaced the reoccuring pattern of appending a number of zeros into a
> call to trailingZeros
>
>  performance difference seemingly at noise levels in micros, but bonus to
> readability and Formatter*.class-files are now a total of 246 bytes smaller
>
> /Claes
>
>
> On 2014-07-14 13:29, Claes Redestad wrote:
>
>> Hi Peter,
>>
>> On 2014-07-14 13:25, Peter Levart wrote:
>>
>>> On 07/14/2014 12:07 PM, Claes Redestad wrote:
>>>
>>>> Hi,
>>>>
>>>>  please review this patch which optimizes away some allocations from
>>>> java.util.Formatter and achieve 1.1-1.3x speedups of micros targetting
>>>> String.format. See bug for more details.
>>>>
>>>>  webrev: http://cr.openjdk.java.net/~redestad/8050142/webrev.0
>>>>  bug: https://bugs.openjdk.java.net/browse/JDK-8050142
>>>>
>>>>  Testing: JPRT, jtreg (java/lang/String, java/util/Formatter),
>>>> SPECjbb2013 and microbenchmarks
>>>>
>>>>  Thanks!
>>>>
>>>>  /Claes
>>>>
>>>
>>> Hi Claes,
>>>
>>> Since justify() result is always appended to the resulting Appendable,
>>> you could merge the functionality and eliminate constructing intermediary
>>> StringBuilder altogether:
>>>
>>> http://cr.openjdk.java.net/~plevart/jdk9-dev/Formatter/webrev.01/
>>>
>>>  Looks good, especially eliminating the need for two different append
>> methods. I'll update based on this and other suggestions.
>>
>> /Claes
>>
>>> Regards, Peter
>>>
>>
>>
>