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Implement fft for g1 values

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This commit is contained in:
danielsanchezq 2024-06-11 18:08:19 +02:00
parent 3620cdc8ae
commit 8d56ab7eb6
1 changed files with 33 additions and 7 deletions
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40
da/kzg_rs/fft.py
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@ -1,7 +1,34 @@
from typing import Sequence
from typing import Sequence, List
from eth2spec.deneb.mainnet import BLSFieldElement
from eth2spec.utils import bls
from da.kzg_rs.common import G1
def fft_g1(vals: Sequence[G1], roots_of_unity: Sequence[BLSFieldElement], modulus: int) -> List[G1]:
if len(vals) == 1:
return vals
L = fft_g1(vals[::2], roots_of_unity[::2], modulus)
R = fft_g1(vals[1::2], roots_of_unity[::2], modulus)
o = [bls.Z1() for _ in vals]
for i, (x, y) in enumerate(zip(L, R)):
y_times_root = bls.multiply(y, roots_of_unity[i])
o[i] = (x + y_times_root)
o[i + len(L)] = x + -y_times_root
return o
def ifft_g1(vals: Sequence[G1], roots_of_unity: Sequence[BLSFieldElement], modulus: int) -> List[G1]:
assert len(vals) == len(roots_of_unity)
# modular inverse
invlen = pow(len(vals), modulus-2, modulus)
return [
bls.multiply(x, invlen)
for x in fft_g1(
vals, [roots_of_unity[0], *roots_of_unity[:0:-1]], modulus
)
]
def _fft(
vals: Sequence[BLSFieldElement],
@ -14,24 +41,23 @@ def _fft(
R = _fft(vals[1::2], roots_of_unity[::2], modulus)
o = [BLSFieldElement(0) for _ in vals]
for i, (x, y) in enumerate(zip(L, R)):
y_times_root = (int(y) * int(roots_of_unity[i])) % modulus
y_times_root = BLSFieldElement((int(y) * int(roots_of_unity[i])) % modulus)
o[i] = BLSFieldElement((int(x) + y_times_root) % modulus)
o[i + len(L)] = BLSFieldElement((int(x) - y_times_root + modulus) % modulus)
o[i + len(L)] = BLSFieldElement((int(x) - int(y_times_root) + modulus) % modulus)
return o
def fft(vals, root_of_unity, modulus):
assert len(vals) == len(root_of_unity)
return _fft(vals, root_of_unity, modulus)
def ifft(vals, root_of_unity, modulus):
assert len(vals) == len(root_of_unity)
def ifft(vals, roots_of_unity, modulus):
assert len(vals) == len(roots_of_unity)
# modular inverse
invlen = pow(len(vals), modulus-2, modulus)
return [
BLSFieldElement((int(x) * invlen) % modulus)
for x in _fft(
vals, [root_of_unity[0], *root_of_unity[:0:-1]], modulus
vals, [roots_of_unity[0], *roots_of_unity[:0:-1]], modulus
)
]