This is a pet peeve of mine: there is a table with benchmark nrs but no link to code to verify this. And in the case of JavaScript benchmarks, no explanation gi

This is a pet peeve of mine: there is a table with benchmark nrs but no link to code to verify this. And in the case of JavaScript benchmarks, no explanation given for which JS engine was used either. So I just did it myself. Maybe I made a mistake in porting it but at least you can verify and fix the benchmarks yourself now in that case. Your intuition seems correct, because the optimized version is slower for me - both on Firefox nor on Chrome. But using the Math.clz32 version I suggested elsewhere is always faster. One other issue I have is with using () => {} as the callback. So I added a stateful callback with a small side-effect to verify whether or not this loop optimization even matters, or whether the callback overhead should be expected to dwarf it. The results do suggest optimizing the loop is worth it. I also tried using a Uint32Array backing array, which has identical performance! That is a good sign regarding plain array optimizations[1]. On lower values the optimized options are faster, as expected although the clz32 does significantly better, and in the case of Firefox helps it (almost) catch up to Chrome. [0] https://jsbenchit.org/?src=219dd9ed01e98533590fc8de40c886f4 https://jsbenchit.org/?src=219dd9ed01e98533590fc8de40c886f4 fully set [1] https://jsbenchit.org/?src=b82e3a2e9631f5e781fc9ff796072985 https://jsbenchit.org/?src=b82e3a2e9631f5e781fc9ff796072985 fully set, typed array [2] https://jsbenchit.org/?src=2dc59964ac15bbc22d58f1f9ee0a6d3e https://jsbenchit.org/?src=2dc59964ac15bbc22d58f1f9ee0a6d3e 50% randomly set [3] https://jsbenchit.org/?src=3faa2eb84da523890923549c3b316f2e https://jsbenchit.org/?src=3faa2eb84da523890923549c3b316f2e 25% randomly set in lower half [4] https://jsbenchit.org/?src=646bf8088d0cd2808e236518b7eaa944 https://jsbenchit.org/?src=646bf8088d0cd2808e236518b7eaa944 one random bit set per word [5] https://jsbenchit.org/?src=4982f7e3557153267e23b4a88732d6a4 https://jsbenchit.org/?src=4982f7e3557153267e23b4a88732d6a4 one random bit set every two words [6] https://jsbenchit.org/?src=e4ac3cb90b4a395dd7a873fd51267d48 https://jsbenchit.org/?src=e4ac3cb90b4a395dd7a873fd51267d48 empty bitset (sanity check)