On Sun, 17 Sep 2023 16:01:33 GMT, Shaojin Wen <d...@openjdk.org> wrote:
> @cl4es made performance optimizations for the simple specifiers of > String.format in PR https://github.com/openjdk/jdk/pull/2830. Based on the > same idea, I continued to make improvements. I made patterns like %2d %02d > also be optimized. > > The following are the test results based on MacBookPro M1 Pro: > > > -Benchmark Mode Cnt Score Error Units > -StringFormat.complexFormat avgt 15 1862.233 ? 217.479 ns/op > -StringFormat.int02Format avgt 15 312.491 ? 26.021 ns/op > -StringFormat.intFormat avgt 15 84.432 ? 4.145 ns/op > -StringFormat.longFormat avgt 15 87.330 ? 6.111 ns/op > -StringFormat.stringFormat avgt 15 63.985 ? 11.366 ns/op > -StringFormat.stringIntFormat avgt 15 87.422 ? 0.147 ns/op > -StringFormat.widthStringFormat avgt 15 250.740 ? 32.639 ns/op > -StringFormat.widthStringIntFormat avgt 15 312.474 ? 16.309 ns/op > > +Benchmark Mode Cnt Score Error Units > +StringFormat.complexFormat avgt 15 740.626 ? 66.671 ns/op > (+151.45) > +StringFormat.int02Format avgt 15 131.049 ? 0.432 ns/op > (+138.46) > +StringFormat.intFormat avgt 15 67.229 ? 4.155 ns/op > (+25.59) > +StringFormat.longFormat avgt 15 66.444 ? 0.614 ns/op > (+31.44) > +StringFormat.stringFormat avgt 15 62.619 ? 4.652 ns/op (+2.19) > +StringFormat.stringIntFormat avgt 15 89.606 ? 13.966 ns/op (-2.44) > +StringFormat.widthStringFormat avgt 15 52.462 ? 15.649 ns/op > (+377.95) > +StringFormat.widthStringIntFormat avgt 15 101.814 ? 3.147 ns/op > (+206.91) src/java.base/share/classes/java/util/FormatProcessor.java line 234: > 232: } > 233: > 234: char c = fragment.charAt(i); I think that `c` can be checked against `%` or `n` right here. A consequence is that the parser will never be `reset()` and there's no need for the `if` below. src/java.base/share/classes/java/util/FormatProcessor.java line 257: > 255: group = fragment.substring(i - 1, i + off + 1); > 256: } else { > 257: group = String.valueOf(c); The original code throws when (1) there is a match _and_ (2) it is not at the end of the fragment or it is not needed. AFAIU, here, `off` can only be `0`, which means that the parser didn't find a match. Throwing an exception is different behavior than the original code. Let me know if I'm wrong with my understanding of the proposed code. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/15776#discussion_r1362465703 PR Review Comment: https://git.openjdk.org/jdk/pull/15776#discussion_r1362469833
