Small number parsing fast path

[konstin]

We found that replacing

let value = number.as_str().parse::<BigInt>().unwrap();

with

// Optimization: `Natural` and thereby `Integer` add up digits from bytes to convert
// from string. This is much less efficient than the highly optimized std
// string-to-number parser and we know that most numbers are small.
// i32::MAX is 2147483647 (10 digits), so all 9 digit numbers are representable as
// i32. We can't guarantee that `32_bit_limbs` isn't set, so we limit ourselves to
// i32 instead of i64.
let value = if number.as_str().len() < 10 {
    Integer::from(i32::from_str(number.as_str()).unwrap())
} else {
   Integer::from_str(number.as_str()).unwrap()
};

for cases where we know that radix is 10 gives a significant speedup for our use case (parsing a lot of number which are generally small). It would be great if malachite would natively contain such an optimization, which could be extended by e.g. checking whether the first by is -.

[mhogrefe]

Thanks for pointing this out. I'll include this optimization in the next release.

[mhogrefe]

Fixed in 0.4.3.

See https://github.com/mhogrefe/malachite/blob/v0.4.3/malachite-nz/src/natural/conversion/string/from_string.rs#L204; that is the optimization for Naturals, and the Integer and Rational parsing code forwards to it.

[mhogrefe]

Sorry, v0.4.3 had some wrong dependencies. Please use v0.4.4 instead.