diff options
Diffstat (limited to 'doc/source/reference/random/parallel.rst')
| -rw-r--r-- | doc/source/reference/random/parallel.rst | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/doc/source/reference/random/parallel.rst b/doc/source/reference/random/parallel.rst index 2f79f22d8..721584014 100644 --- a/doc/source/reference/random/parallel.rst +++ b/doc/source/reference/random/parallel.rst @@ -18,10 +18,10 @@ a `~BitGenerator`. It uses hashing techniques to ensure that low-quality seeds are turned into high quality initial states (at least, with very high probability). -For example, `~mt19937.MT19937` has a state consisting of 624 +For example, `MT19937` has a state consisting of 624 `uint32` integers. A naive way to take a 32-bit integer seed would be to just set the last element of the state to the 32-bit seed and leave the rest 0s. This is -a valid state for `~mt19937.MT19937`, but not a good one. The Mersenne Twister +a valid state for `MT19937`, but not a good one. The Mersenne Twister algorithm `suffers if there are too many 0s`_. Similarly, two adjacent 32-bit integer seeds (i.e. ``12345`` and ``12346``) would produce very similar streams. @@ -91,15 +91,15 @@ territory ([2]_). .. [2] In this calculation, we can ignore the amount of numbers drawn from each stream. Each of the PRNGs we provide has some extra protection built in that avoids overlaps if the `~SeedSequence` pools differ in the - slightest bit. `~pcg64.PCG64` has :math:`2^{127}` separate cycles + slightest bit. `PCG64` has :math:`2^{127}` separate cycles determined by the seed in addition to the position in the :math:`2^{128}` long period for each cycle, so one has to both get on or near the same cycle *and* seed a nearby position in the cycle. - `~philox.Philox` has completely independent cycles determined by the seed. - `~sfc64.SFC64` incorporates a 64-bit counter so every unique seed is at + `Philox` has completely independent cycles determined by the seed. + `SFC64` incorporates a 64-bit counter so every unique seed is at least :math:`2^{64}` iterations away from any other seed. And - finally, `~mt19937.MT19937` has just an unimaginably huge period. Getting - a collision internal to `~SeedSequence` is the way a failure would be + finally, `MT19937` has just an unimaginably huge period. Getting + a collision internal to `SeedSequence` is the way a failure would be observed. .. _`implements an algorithm`: http://www.pcg-random.org/posts/developing-a-seed_seq-alternative.html @@ -113,10 +113,10 @@ territory ([2]_). Independent Streams ------------------- -:class:`~philox.Philox` is a counter-based RNG based which generates values by +`Philox` is a counter-based RNG based which generates values by encrypting an incrementing counter using weak cryptographic primitives. The seed determines the key that is used for the encryption. Unique keys create -unique, independent streams. :class:`~philox.Philox` lets you bypass the +unique, independent streams. `Philox` lets you bypass the seeding algorithm to directly set the 128-bit key. Similar, but different, keys will still create independent streams. |