On Sat, 26 Apr 2025 17:22:09 GMT, Chen Liang <[email protected]> wrote:
>> src/java.base/share/classes/java/math/BigInteger.java line 2721:
>>
>>> 2719: if (!pow.equals(ONE)) {
>>> 2720: for (int i = 0; i < blockLen; i++)
>>> 2721: pow = pow.multiply(pow);
>>
>> Majority of the time we have `blockLen == maxExpLen`. We should cache that
>> pow-to-maxExpLen result too, if we have `maxExpLen >= nLen` initially. Maybe
>> also calculate power-to-`nLen % maxExpLen` as that will be used in the final
>> round of the loop.
>
> No, pow is always being modified, ignore this, my bad.
> Majority of the time we have `blockLen == maxExpLen`. We should cache that
> pow-to-maxExpLen result too, if we have `maxExpLen >= nLen` initially. Maybe
> also calculate power-to-`nLen % maxExpLen` as that will be used in the final
> round of the loop.
I don't get the point, since `pow` changes its value at every iteration and
here the property of the "power of a power" is used, i.e. `pow^(2^n) ==
(((pow^2)^2)...)^2` `n` times to shift the exponent of the power, so I don't
see how caching pow-to-maxExpLen would be useful.
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PR Review Comment: https://git.openjdk.org/jdk/pull/24690#discussion_r2061511811
