def robust_decode(self, z, encoded):
x = [self.point(zi).value for zi in z]
args = [x, encoded, self.d + 1, self.modulus]
if self.use_omega_powers:
args += [z, self.point.omega.value, self.point.order]
decoded, error_poly = gao_interpolate(
*args, use_omega_powers=self.use_omega_powers)
if decoded is None:
return None, None
errors = []
if len(error_poly) > 1:
if self.use_omega_powers:
err_eval = fft(error_poly, self.point.omega.value,
self.modulus, self.point.order)[:self.point.n]
else:
x = [self.point(i).value for i in range(self.point.n)]
err_eval = vandermonde_batch_evaluate(x, [error_poly],
self.modulus)[0]
errors = [i for i in range(self.point.n) if err_eval[i] == 0]
return decoded, errors
def test_fft():
# Given
coeffs = [0, 1]
p = 13
omega = 5
n = 4
# When
fft_rep = fft(coeffs, omega, p, n)
# Then
assert fft_rep == [1, 5, 12, 8]
def test_fft_big(galois_field, galois_field_roots):
# Given
d = 20
p = galois_field.modulus
r = 5
n = 2**r
omega = galois_field_roots[r]
coeffs = [galois_field.random().value for _ in range(d)]
# When
fft_rep = fft(coeffs, omega, p, n)
# Then
assert len(fft_rep) == n
for i in range(n):
x = pow(omega, i, p)
assert fft_rep[i] == sum(coeffs[j] * pow(x, j, p)
for j in range(d)) % p
def encode_one(self, data):
return fft(data, self.omega, self.modulus, self.order)[:self.n]
