RFR: 8334755: Asymptotically faster implementation of square root algorithm [v30]

[Raffaello Giulietti]

On Thu, 18 Jul 2024 14:49:19 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> I did it, although I'm afraid it takes up too much running time due to the overhead of BigInteger's wrapping...
>
> I mean only restricted to unsigned `long` perfect squares, something like the following, but written as a proper test
> 
> 
>         long i = 0;
>         for (; i < 1L << 32; ++i) {
>             long x = i * i;
>             long s = (long) Math.sqrt(x >= 0 ? x : x + 0x1p64);
>             if (!(s + 1 == i || s == i)) {
>                 System.out.format("oops... i=%d, but s=%d%n", i, s);
>                 System.exit(1);
>             }
>         }

It takes about 5 s on my laptop.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19710#discussion_r1682990602