Improve performances of BigDecimal.numberOfDecimalDigits().

[glureau]

During a performance study on our app, we notice that numberOfDecimalDigits was taking a lot of time during our calculations.

I've made an adjustment and processed to a simple benchmark on a M3 Pro with this test

    @Test
    fun perfTest() {
        val bd = BigDecimal.parseString("1.0")
        val duration = measureTime {
            repeat(1_000_000) { bd.numberOfDecimalDigits() }
        }
        println("Duration: $duration")
    }

Initial results before the changes:

platform	Run #1	Run #2	Run #3
iosSimulator	19.12s	17.95s	17.91s
JVM	536ms	538.7ms	559.1ms
macosArm64	18.2s	18.3s	18.1s

After the changes of the first commit, I obtain

platform	Run #1	Run #2	Run #3	Comparison best of 3
iosSimulator	2.02s	2.01s	2.10s	reduction of 88%
JVM	90.6ms	75.2ms	88.5ms	reduction of 86%
macosArm64	2.10s	2.06s	2.07s	reduction of 88%

Major changes:

• removeTrailingZeroes is comparing with == ZERO which has quite a big impact (I would like to suggest a second commit where I change all of them by isZero() which is more powerful and gives the same result if I'm right.
• removeTrailingZeroes needs to maintain reminder/quotient which requires another check, more memory allocation and is eventually 3x more time (JVM) than my proposal.

[CLAassistant]

All committers have signed the CLA.

[ionspin]

Thank you for the great work! If you can sort out the CLA-Assistant we could get this meged! And don't worry about signing commits, that part I can skip.

[glureau]

Thank you! It would be wonderful if I can get a release with that change soon. 🙏🏻 Also I'm a bit confused, I've signed it but the bot still say it's not signed :(

[ionspin]

I think the actual commit has to have the same email address you used to sign up with GitHub, I haven't read this article but I feel it's roughly in the direction of the solution :) https://docs.github.com/en/pull-requests/committing-changes-to-your-project/troubleshooting-commits/why-are-my-commits-linked-to-the-wrong-user

Oh and for the release, as soon as we merge it should be available in snapshot version.

[glureau]

It required a click on "recheck" 🤦🏻 CLA SIGNED ✅

[glureau]

Also I was expecting CI to run tests as I don't have the best config right now to run them. Should I do something to start them on CI?

EDIT: I'll prepare another PR for replacing all other == ZERO by isZero(), if it make sense to you.

[ionspin]

The CI requires manual approval for pull requests, so no worries I'll run that. As far as replacing == ZERO with isZero to be honest I can't answer right now, I'd have to go through the source and remind myself for that particular case. If you want to submit a pull request with that change, I think that would help have an overview of where it was used.

Also you have an extra bracket in the test that makes it not compile, I'll leave a comment to point it out.

[ionspin]

Merged, thanks once more! Once the CI is complete it will publish new snapshot version

[ionspin]

Deployed, your changes should be available in 0.3.10-SNAPSHOT https://oss.sonatype.org/content/repositories/snapshots/com/ionspin/kotlin/bignum/0.3.10-SNAPSHOT/