def philox(W, N, ctr, key, Nrounds=None):
"""
W: word length (32, 64)
N: number of generated items, 2 or 4
Nrounds: number of rounds (up to 16)
inn: counter, array(N, numpy.uint${W}) --- counter
k: key, array(N/2, numpy.uint${W}) --- key
returns: array(N, numpy.uint${W})
"""
assert W in (32, 64)
assert N in (2, 4)
if Nrounds is None:
Nrounds = 10
assert Nrounds <= 16
with ignore_integer_overflow():
for rnd in range(Nrounds):
ctr = philox_round(W, N, rnd, ctr, key)
return ctr
def threefry(W, N, ctr, key, Nrounds=None):
"""
W: word length (32, 64)
N: number of generated items, 2 or 4
Nrounds: number of rounds (up to 72)
ctr: counter, array(N, numpy.uint${W})
key: key, array(N, numpy.uint${W})
returns: array(N, numpy.uint${W})
Note: for W=64, N=4 and Nrounds=72 it is the same as Threefish algorithm from Skein,
only without the 128-bit "tweak" which is applied to the key.
With this tweak it is possible to upgrade this algorithm from PRNG to QRNG.
"""
assert W in (32, 64)
assert N in (2, 4)
if Nrounds is None:
Nrounds = 20
dtype = numpy.uint32 if W == 32 else numpy.uint64
if N == 2:
assert Nrounds <= 32
ks = numpy.empty(3, dtype)
else:
assert Nrounds <= 72
ks = numpy.empty(5, dtype)
X = numpy.empty(N, dtype)
assert ctr.size == key.size == N
ks[N] = THREEFRY_KS_PARITY[W]
for i in range(N):
ks[i] = key[i]
X[i] = ctr[i]
ks[N] ^= key[i]
# Insert initial key before round 0
for i in range(N):
X[i] += ks[i]
R = THREEFRY_ROTATION[(W, N)]
with ignore_integer_overflow():
for rnd in range(Nrounds):
# FIXME: In the current version of Random123 (1.06),
# there is a bug in R_idx calculation for N == 2, where
# R_idx = rnd % 8 if rnd < 20 else (rnd - 4) % 8
# instead of what goes below.
# When this bug is fixed, Random123 and this implementation
# will start to produce identical results again,
# and this comment can be removed.
R_idx = rnd % 8
if N == 2:
X[0] += X[1]
X[1] = threefry_rotate(W, R[R_idx, 0], X[1])
X[1] ^= X[0]
else:
idx1 = 1 if rnd % 2 == 0 else 3
idx2 = 3 if rnd % 2 == 0 else 1
X[0] += X[idx1]
X[idx1] = threefry_rotate(W, R[R_idx, 0], X[idx1])
X[idx1] ^= X[0]
X[2] += X[idx2]
X[idx2] = threefry_rotate(W, R[R_idx, 1], X[idx2])
X[idx2] ^= X[2]
if rnd % 4 == 3:
for i in range(N):
X[i] += ks[(rnd // 4 + i + 1) % (N + 1)]
X[N-1] += dtype(rnd // 4 + 1)
return X