On Thu, 16 May 2024 11:13:24 GMT, Chen Liang <li...@openjdk.org> wrote:
>> It seems reasonable to assume `null` values are not constant-folded. For >> straight-out-of-the-box usage, there is no apparent significant difference >> as indicated by a new benchmark I just added: >> >> >> Benchmark Mode Cnt Score Error >> Units >> StableStaticBenchmark.atomic thrpt 10 5729.683 ? 502.023 >> ops/us >> StableStaticBenchmark.dcl thrpt 10 6069.222 ? 951.784 >> ops/us >> StableStaticBenchmark.dclHolder thrpt 10 5502.102 ? 1630.627 >> ops/us >> StableStaticBenchmark.stable thrpt 10 12737.158 ? 1746.456 >> ops/us <- Non-null benchmark >> StableStaticBenchmark.stableHolder thrpt 10 12053.978 ? 1421.527 >> ops/us >> StableStaticBenchmark.stableList thrpt 10 12443.870 ? 2084.607 >> ops/us >> StableStaticBenchmark.stableNull thrpt 10 13164.232 ? 591.284 >> ops/us <- Added null benchmark >> StableStaticBenchmark.stableRecordHolder thrpt 10 13638.893 ? 1250.895 >> ops/us >> StableStaticBenchmark.staticCHI thrpt 10 13639.220 ? 1190.922 >> ops/us >> >> >> If the `null` value participates in a much larger constant-folding tree, >> there might be a significant difference. I am afraid moving the order would >> have detrimental effects on instance performance: >> >> Checking value first: >> >> >> Benchmark Mode Cnt Score Error Units >> StableBenchmark.atomic thrpt 10 246.460 ? 75.417 ops/us >> StableBenchmark.dcl thrpt 10 243.481 ? 35.021 ops/us >> StableBenchmark.stable thrpt 10 4977.693 ? 675.926 ops/us >> <- Non-null >> StableBenchmark.stableHoldingList thrpt 10 3614.460 ? 275.140 ops/us >> StableBenchmark.stableList thrpt 10 3328.155 ? 898.202 ops/us >> StableBenchmark.stableListStored thrpt 10 3842.174 ? 535.902 ops/us >> StableBenchmark.stableNull thrpt 10 6217.737 ? 840.376 ops/us >> <- null >> StableBenchmark.supplier thrpt 10 9369.934 ? 1449.182 ops/us >> >> >> Checking null first: >> >> >> Benchmark Mode Cnt Score Error Units >> StableBenchmark.atomic thrpt 10 287.640 ? 17.858 ops/us >> StableBenchmark.dcl thrpt 10 250.398 ? 20.874 ops/us >> StableBenchmark.stable thrpt 10 3745.885 ? 1040.534 ops/us >> <- Non-null >> StableBenchmark.stableHoldingList thrpt 10 2982.129 ? 503.492 ops/us >> StableBenchmar... > > I think the result would be more convincing if the stable case is changed to > `sum += (stable.orThrow() == null ? 0 : 1) + (stable2.orThrow() == null ? 0 : > 1);` as adding by 1 might be somewhat better optimized by JIT. I have instead changed parts of the `stableNull()` body to: sum += (stableNull.orThrow() == null ? VALUE : VALUE2) + (stableNull2.orThrow() == null ? VALUE : VALUE2); ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/18794#discussion_r1603205135
