Long.bitCount micro-optimization

[Brian Burkhalter]

Thanks for running the numbers.

On May 8, 2017, at 5:42 PM, Isaac Levy <isaac.r.levy at gmail.com> wrote:

> bitCountInt      avgt   10  44550.630 ± 2670.294  ns/op

[41880, 47221]

> bitCountIntNew   avgt   10  33904.058 ± 1108.438  ns/op

[32796, 35012]

> bitCountLong     avgt   10  58638.138 ± 3736.014  ns/op

[54902, 62374]

> bitCountLongNew  avgt   10  38700.601 ±  526.648  ns/op

[38174, 39227]

So the ranges don’t overlap which is important.

> JDK 1.8.0_131, 2.3ghz Core i7, each run counting numbers 0 to 2^14


Thing is one needs to run the benchmark on a variety of hardware. I went through a lot of this sort of thing myself when evaluating among other things for example the crossover thresholds for the Karatsuba and Toom-Cook multiplication algorithms in BigInteger multiplication. There was a lot of variation.

Thanks,

Brian