On Mon, 13 Feb 2023 16:10:14 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> We can improve various String methods such as `startsWith`, `endsWith` and
>> `regionMatches` by leveraging the intrinsified mismatch methods in
>> `ArraysSupport`.
>
> Claes Redestad has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Clarify coder shift in startsWith
Case-insensitive regionMatches could be improved by using
ArraysSupport.mismatch to skip over long common substrings:
PR:
Benchmark (size) (utf16) Mode Cnt Score Error
Units
StringComparisons.regionMatchesCI 6 false avgt 15 8.248 ± 0.427
ns/op
StringComparisons.regionMatchesCI 15 false avgt 15 11.408 ± 0.429
ns/op
StringComparisons.regionMatchesCI 1024 false avgt 15 328.796 ± 7.191
ns/op
Arrays.mismatch:
Benchmark (size) (utf16) Mode Cnt Score Error
Units
StringComparisons.regionMatchesCI 6 false avgt 15 10.608 ± 0.302
ns/op
StringComparisons.regionMatchesCI 15 false avgt 15 8.772 ± 0.347
ns/op
StringComparisons.regionMatchesCI 1024 false avgt 15 31.070 ± 1.783
ns/op
Patch on top of your PR:
Index: src/java.base/share/classes/java/lang/StringLatin1.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/src/java.base/share/classes/java/lang/StringLatin1.java
b/src/java.base/share/classes/java/lang/StringLatin1.java
--- a/src/java.base/share/classes/java/lang/StringLatin1.java (revision
6cac333d8f9f34e16168447c60f28a6b0d31623f)
+++ b/src/java.base/share/classes/java/lang/StringLatin1.java (date
1676305817928)
@@ -384,6 +384,14 @@
byte[] other, int ooffset, int len) {
int last = toffset + len;
while (toffset < last) {
+ int mismatch = ArraysSupport.mismatch(value, toffset, other,
ooffset, len);
+ if (mismatch == -1) {
+ return true;
+ } else {
+ toffset += mismatch;
+ ooffset += mismatch;
+ len -= mismatch + 1;
+ }
char c1 = (char)(value[toffset++] & 0xff);
char c2 = (char)(other[ooffset++] & 0xff);
if (c1 == c2) {
Index: test/micro/org/openjdk/bench/java/lang/StringComparisons.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/test/micro/org/openjdk/bench/java/lang/StringComparisons.java
b/test/micro/org/openjdk/bench/java/lang/StringComparisons.java
--- a/test/micro/org/openjdk/bench/java/lang/StringComparisons.java
(revision 6cac333d8f9f34e16168447c60f28a6b0d31623f)
+++ b/test/micro/org/openjdk/bench/java/lang/StringComparisons.java (date
1676305817914)
@@ -49,6 +49,7 @@
public String endsWithA;
public String endsWithB;
public String startsWithA;
+ public String endsWitha;
@Setup
public void setup() {
@@ -56,6 +57,7 @@
string = c.repeat(size);
equalString = c.repeat(size);
endsWithA = c.repeat(size).concat("A");
+ endsWitha = c.repeat(size).concat("a");
endsWithB = c.repeat(size).concat("B");
startsWithA = "A" + (c.repeat(size));
}
@@ -75,6 +77,11 @@
return endsWithA.regionMatches(0, endsWithB, 0, endsWithB.length());
}
+ @Benchmark
+ public boolean regionMatchesIC() {
+ return endsWithA.regionMatches(true,0, endsWitha, 0,
endsWitha.length());
+ }
+
@Benchmark
public boolean regionMatchesRange() {
return startsWithA.regionMatches(1, endsWithB, 0, endsWithB.length() -
1);
-------------
PR: https://git.openjdk.org/jdk/pull/12528
