On Wed, 6 Sep 2023 16:10:23 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> src/java.base/share/classes/java/util/HexFormat.java line 644:
>>
>>> 642: return (char)('a' - 10 + value);
>>> 643: }
>>> 644: return (char)('A' - 10 + value);
>>
>> Not sure if this would adversely impact performance, but what about
>> factoring out these lines in a private method? They are repeated in
>> `toHighHexDigit`.
>
> Surprisingly this does carry some cost in the microbenchmarks on my M1. Might
> be noise, but it seems rather consistent so I'll need to investigate.
This:
diff --git a/src/java.base/share/classes/java/util/HexFormat.java
b/src/java.base/share/classes/java/util/HexFormat.java
index 107c362cbc2..177548c03f7 100644
--- a/src/java.base/share/classes/java/util/HexFormat.java
+++ b/src/java.base/share/classes/java/util/HexFormat.java
@@ -634,14 +634,7 @@ private static String escapeNL(String string) {
* @return the hexadecimal character for the low 4 bits {@code 0-3} of the
value
*/
public char toLowHexDigit(int value) {
- value = value & 0xf;
- if (value < 10) {
- return (char)('0' + value);
- }
- if (digitCase == Case.LOWERCASE) {
- return (char)('a' - 10 + value);
- }
- return (char)('A' - 10 + value);
+ return toHexDigit(value & 0xf);
}
/**
@@ -655,7 +648,10 @@ public char toLowHexDigit(int value) {
* @return the hexadecimal character for the bits {@code 4-7} of the value
*/
public char toHighHexDigit(int value) {
- value = (value >> 4) & 0xf;
+ return toHexDigit((value >> 4) & 0xf);
+ }
+
+ private char toHexDigit(int value) {
if (value < 10) {
return (char)('0' + value);
}
.. clearly increase cost across all micros:
Name Cnt Base Error Test Error Unit
Diff%
HexFormatBench.appenderLower 15 1,046 ± 0,041 1,301 ± 0,017 us/op
-24,4% (p = 0,000*)
HexFormatBench.appenderLowerCached 15 1,056 ± 0,055 1,175 ± 0,115 us/op
-11,3% (p = 0,001*)
HexFormatBench.appenderUpper 15 1,059 ± 0,055 1,303 ± 0,012 us/op
-23,0% (p = 0,000*)
HexFormatBench.appenderUpperCached 15 1,099 ± 0,014 1,451 ± 0,267 us/op
-32,0% (p = 0,000*)
HexFormatBench.toHexLower 15 0,322 ± 0,002 0,338 ± 0,005 us/op
-4,8% (p = 0,000*)
HexFormatBench.toHexLowerCached 15 0,324 ± 0,003 0,411 ± 0,005 us/op
-27,0% (p = 0,000*)
HexFormatBench.toHexUpper 15 0,324 ± 0,003 0,340 ± 0,003 us/op
-4,9% (p = 0,000*)
HexFormatBench.toHexUpperCached 15 0,322 ± 0,001 0,411 ± 0,004 us/op
-27,6% (p = 0,000*)
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/15591#discussion_r1317728161
