Foreign field backend #203
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| */ | ||
| function computeFieldConstants(p: bigint) { | ||
| // figure out the factorization p - 1 = 2^M * t | ||
| let oddFactor = p - 1n; |
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Nit: the names make it somewhat hard to read.
Is p - 1n necessarily odd? If p is a prime number, as its naming can also suggest, then oddFactor usually starts by being even (and stays so by subsequent >> 1n). In any case. it's not ensured by the parameter type.
Maybe that's the right name, though. Can you refer to a source where this is used/defined?
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The code right below that line divides oddFactor by 2 as many times as needed to become odd.
so this code, as the comment hints at (but could've used clearer naming), figures out the factorization
p - 1 = 2^twoadicity * oddFactor, for a prime p (well for any number)
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we need the oddFactor in some algorithms -- for example, right below in the same function to find a primitive root of unity
This PR generalizes the bigint finite field code to work for all fields.
This enables foreign field tests in o1-labs/o1js#1220
We also add a file with a range of concrete finite fields that can be used for testing and in examples.