Speed up strongRound by avoiding string casting

[marvinhagemeister]

I'm currently profiling my build pipeline and noticed that the strongRound function showed up a couple of times, followed immediately with a bit of GC cleanup shortly after. We can speed up that function by avoiding the string casting caused by Number.prototype.toFixed().

In my project's build pipeline with lots of svg icons this saves about 1.4s in total.

[marvinhagemeister]

Alright CI is now passing here too. Didn't account for the powCache needing to expand to floatPrecision + 1 instead of just floatPrecision due to the narrowing logic in strongRound in my earlier version of the PR.

[marvinhagemeister]

Totally forgot about the ** operator. I think that's a cleaner approach compared to caching it and the precision value is typically rather low. Don't see a meaningful difference between the two when profiling.

[bnoordhuis]

Hi @marvinhagemeister, I was reading your blog post and I noticed this potential issue:

precision can go up to 19 if I read this file right (but seems to default to 3?) so you can lose some... ah, er... precision when multiplying it with another large number:

Math.round(Number.MAX_SAFE_INTEGER * 10**19) / 10**19  // off by one
Math.round(4294967295 * 10**19) / 10**19  // 4294967295.0000005
Math.round(16777215 * 10**19) / 10**19  // 16777214.999999998

I assume that's okay here because num won't be that big but I can't say for sure from context.

[marvinhagemeister]

Good catch, yeah with higher precision values this can become an issue. The precision setting is typically used to reduce precision to make the SVG smaller. So far I've only seen precision settings of 1-3 in the wild.