8315585: Optimization for decimal to string #23310

wenshao · 2025-01-25T07:25:40Z

Continue to complete PR #16006 and PR #21593 to improve BigDecimal::toString and BigDecimal::toPlainString performance and reduce duplicate code

Progress

Change must not contain extraneous whitespace
Commit message must refer to an issue
Change must be properly reviewed (2 reviews required, with at least 2 Reviewers)

Issue

JDK-8315585: Optimization for decimal to string (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/23310/head:pull/23310
$ git checkout pull/23310

Update a local copy of the PR:
$ git checkout pull/23310
$ git pull https://git.openjdk.org/jdk.git pull/23310/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 23310

View PR using the GUI difftool:
$ git pr show -t 23310

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/23310.diff

Using Webrev

Link to Webrev Comment

bridgekeeper · 2025-01-25T07:26:28Z

👋 Welcome back swen! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-01-25T07:26:37Z

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

openjdk · 2025-01-25T07:27:07Z

@wenshao The following label will be automatically applied to this pull request:

core-libs

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

j3graham · 2025-01-25T07:43:29Z

src/java.base/share/classes/jdk/internal/util/DecimalDigits.java

-     * @param buf   target buffer, UTF16-coded.
-     * @return index of the most significant digit or minus sign, if present
-     */
-    public static int getChars(long i, int index, char[] buf) {


Before dropping this method, there is another candidate to use it here :

jdk/src/java.base/share/classes/jdk/internal/math/FloatingDecimal.java

Line 367 in 1d2eb2f

private void developLongDigits( int decExponent, long lvalue, int insignificantDigits ){

I took a look at the FloatingDecimal related code. The relevant code in FloatingDecimal can be refactored and simplified so that the removed code does not need to be used.

I submitted a PR to simplify FloatingDecimal #23311

liach · 2025-01-26T18:43:35Z

A great cleanup that consolidates scale2, unscaledAbsString, and unscaledString.

j3graham · 2025-01-26T19:31:08Z

src/java.base/share/classes/java/math/BigDecimal.java

        } else if (insertionPoint > 0) { /* Point goes inside intVal */
-            buf = new StringBuilder(intString);
-            buf.insert(insertionPoint, '.');
+            buf = new StringBuilder();


Could calculate the precise size for the StringBuilder

The performance will degrade if you precompute the length of the StringBuilder.

That’s interesting - should the precomputed lengths be removed in the other ones as well?

j3graham · 2025-01-26T19:32:29Z

src/java.base/share/classes/java/math/BigDecimal.java

-                buf.insert(0, '-');
+                buf.append('-');
+            buf.append(intString)
+                    .insert(insertionPoint + (signum < 0 ? 1 : 0), '.');


Instead of the insert, could do an append of the prefix, then dot, then the suffix.

buf.append(intString, 0, insertionPoint) .append('.') .append(intString, insertionPoint, intString.length());

This is another way to write it, but the performance will be reduced.

j3graham · 2025-01-26T19:52:08Z

src/java.base/share/classes/java/math/BigDecimal.java

+    }
+
+    private String layoutCharsE(boolean sci, String coeff, int coeffLen, long adjusted) {
+        StringBuilder buf = new StringBuilder(32);


The comment above about constructing a buffer probably belongs here. Also could calculate a better approximation of the size - possibly coeffLen+14 if that comment is accurate.

This reverts commit ddc2a86.

bridgekeeper · 2025-05-04T19:45:32Z

@wenshao This pull request has been inactive for more than 8 weeks and will now be automatically closed. If you would like to continue working on this pull request in the future, feel free to reopen it! This can be done using the /open pull request command.

# Conflicts: # src/java.base/share/classes/java/math/BigDecimal.java # src/java.base/share/classes/jdk/internal/util/DecimalDigits.java # test/micro/org/openjdk/bench/java/math/BigDecimals.java

wenshao · 2025-05-25T09:46:42Z

/open

openjdk · 2025-05-25T09:47:29Z

@wenshao This pull request is now open

bridgekeeper · 2025-07-20T14:51:03Z

@wenshao This pull request has been inactive for more than 8 weeks and will be automatically closed if another 8 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

wenshao · 2025-07-20T23:27:05Z

/touch

openjdk · 2025-07-20T23:28:07Z

@wenshao The pull request is being re-evaluated and the inactivity timeout has been reset.

openjdk · 2025-08-20T22:14:32Z

@wenshao this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout dec_to_str_202501
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

# Conflicts: # src/java.base/share/classes/java/math/BigDecimal.java

…Latin1Bytes Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

bridgekeeper · 2025-10-19T04:04:52Z

@wenshao This pull request has been inactive for more than 8 weeks and will be automatically closed if another 8 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

wenshao · 2025-10-20T00:37:24Z

/touch

openjdk · 2025-10-20T00:39:11Z

@wenshao The pull request is being re-evaluated and the inactivity timeout has been reset.

bridgekeeper · 2025-12-15T02:39:55Z

@wenshao This pull request has been inactive for more than 8 weeks and will be automatically closed if another 8 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

wenshao · 2025-12-15T05:57:54Z

/touch

openjdk · 2025-12-15T05:58:15Z

@wenshao The pull request is being re-evaluated and the inactivity timeout has been reset.

src/java.base/share/classes/java/math/BigDecimal.java

liach · 2025-12-15T23:30:06Z

src/java.base/share/classes/java/math/BigDecimal.java

+            buf.append(coeff.charAt(0)); // first character
+            if (coeffLen > 1) {          // more to come
+                buf.append('.')
+                   .append(coeff, 1, coeffLen);


Is this right that the old end is coeffLen - 1 but the new end is coeffLen? I don't see why there should be no more -1.

src/java.base/share/classes/java/math/BigDecimal.java

wenshao added 2 commits January 25, 2025 11:26

add benchmark

4040d76

optimize toString/toPlainString

635882f

wenshao marked this pull request as draft January 25, 2025 07:26

openjdk bot added the core-libs core-libs-dev@openjdk.org label Jan 25, 2025

j3graham reviewed Jan 25, 2025

View reviewed changes

wenshao added 4 commits January 25, 2025 22:16

optimize scale2

7ed19c8

static scale2

7b82f78

optimize scale2 int

edffa0f

bug fix

72ed1b7

j3graham reviewed Jan 26, 2025

View reviewed changes

wenshao added 12 commits January 27, 2025 09:35

bug fix

cb6786b

code style

57cc7b2

use getBytes & JLA instead of StringBuilder

0d2b3aa

code style

4a857cf

code style

057d006

revert use StringBuilder

a41a34b

from @j3graham

a734f61

intCompact getValueString & int scale2

3ed3354

remove unnecessary abs

d99a963

simplify scale2

ddc2a86

Revert "simplify scale2"

d78b07c

This reverts commit ddc2a86.

refactor

4ee8837

wenshao changed the title ~~Optimization for decimal to string~~ 8315585 : Optimization for decimal to string Jan 27, 2025

wenshao changed the title ~~8315585 : Optimization for decimal to string~~ 8315585: Optimization for decimal to string Jan 27, 2025

Merge remote-tracking branch 'upstream/master' into dec_to_str_202501

a5a07ce

bridgekeeper bot closed this May 4, 2025

Merge remote-tracking branch 'upstream/master' into dec_to_str_202501

b4c142d

# Conflicts: # src/java.base/share/classes/java/math/BigDecimal.java # src/java.base/share/classes/jdk/internal/util/DecimalDigits.java # test/micro/org/openjdk/bench/java/math/BigDecimals.java

openjdk bot reopened this May 25, 2025

wenshao marked this pull request as draft May 25, 2025 09:47

openjdk bot removed the rfr Pull request is ready for review label May 25, 2025

wenshao mentioned this pull request Jun 14, 2025

8365832: Optimize FloatingDecimal and DigitList with byte[] and cleanup #23311

Closed

3 tasks

openjdk bot added the merge-conflict Pull request has merge conflict with target branch label Aug 20, 2025

Merge remote-tracking branch 'upstream/master' into dec_to_str_202501

3c3b740

# Conflicts: # src/java.base/share/classes/java/math/BigDecimal.java

openjdk bot removed the merge-conflict Pull request has merge conflict with target branch label Aug 23, 2025

Refactor BigDecimal string creation to use JLA.uncheckedNewStringWith…

d7e2934

…Latin1Bytes Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

liach reviewed Dec 15, 2025

View reviewed changes

wenshao added 4 commits December 16, 2025 09:14

getValueString -> getCompactValueString, from @liach

50c21ca

comments, from @liach

a95ef6e

simplify layoutChars

2345fb9

Merge remote-tracking branch 'upstream/master' into dec_to_str_202501

32d95b3

wenshao requested a review from liach December 16, 2025 06:23

8315585: Optimization for decimal to string #23310

Are you sure you want to change the base?

8315585: Optimization for decimal to string #23310

Conversation

wenshao commented Jan 25, 2025 • edited by openjdk bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Progress

Issue

Reviewing

Uh oh!

bridgekeeper bot commented Jan 25, 2025

Uh oh!

openjdk bot commented Jan 25, 2025

Uh oh!

openjdk bot commented Jan 25, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

liach commented Jan 26, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

bridgekeeper bot commented May 4, 2025

Uh oh!

wenshao commented May 25, 2025

Uh oh!

openjdk bot commented May 25, 2025

Uh oh!

bridgekeeper bot commented Jul 20, 2025

Uh oh!

wenshao commented Jul 20, 2025

Uh oh!

openjdk bot commented Jul 20, 2025

Uh oh!

openjdk bot commented Aug 20, 2025

Uh oh!

bridgekeeper bot commented Oct 19, 2025

Uh oh!

wenshao commented Oct 20, 2025

Uh oh!

openjdk bot commented Oct 20, 2025

Uh oh!

bridgekeeper bot commented Dec 15, 2025

Uh oh!

wenshao commented Dec 15, 2025

Uh oh!

openjdk bot commented Dec 15, 2025

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Milestone

Development

Uh oh!

5 participants

wenshao commented Jan 25, 2025 •

edited by openjdk bot

Loading

openjdk bot commented Jan 25, 2025 •

edited

Loading