manual_seed

→None

manual_seed(seed: _int)

source

Set the seed of the default Philox counter-based random number generator.

The Lucid RNG uses a Philox-4×32 counter-based PRNG (Salmon et al., 2011). Unlike stateful RNGs (e.g. Mersenne Twister), Philox is a keyed bijection: given a 64-bit key $k$ (the seed) and a 64-bit counter $c$ , it produces a deterministic 128-bit output block via 10 rounds of the Philox permutation:

(r_0, r_1, r_2, r_3) = \text{Philox}_{4 \times 32}(k,\, c)

Setting the seed to a fixed value $k_0$ fully determines the entire subsequent sampling stream, enabling reproducible experiments.

Parameters

seedint

Non-negative 64-bit integer seed. The same seed always produces the same sequence of random values on the same hardware.

Notes

Calling manual_seed resets the counter to $0$ in addition to updating the key $k$ . Two calls with the same seed produce identical streams regardless of how many samples were drawn in between.

For multi-process reproducibility, seed each worker with a distinct derived seed, e.g. manual_seed(base_seed + worker_id), to avoid correlated streams across processes.

Examples

>>> import lucid
>>> lucid.manual_seed(42)
>>> a = lucid.rand(3)
>>> lucid.manual_seed(42)
>>> b = lucid.rand(3)
>>> (a - b).abs().max().item()
0.0