RFR [9]: 8050142: Optimize java.util.Formatter (original) (raw)

Andrej Golovnin andrej.golovnin at gmail.com
Mon Jul 14 13:09:07 UTC 2014

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

More information about the core-libs-dev mailing list