diff options
Diffstat (limited to 'lib/stdlib/doc/src/rand.xml')
| -rw-r--r-- | lib/stdlib/doc/src/rand.xml | 61 |
1 files changed, 55 insertions, 6 deletions
diff --git a/lib/stdlib/doc/src/rand.xml b/lib/stdlib/doc/src/rand.xml index 21f680a0ee..25eec216ef 100644 --- a/lib/stdlib/doc/src/rand.xml +++ b/lib/stdlib/doc/src/rand.xml @@ -67,6 +67,26 @@ <p>Xorshift1024*, 64 bits precision and a period of 2^1024-1</p> <p>Jump function: equivalent to 2^512 calls</p> </item> + <tag><c>exro928ss</c></tag> + <item> + <p>Xoroshiro928**, 58 bits precision and a period of 2^928-1</p> + <p>Jump function: equivalent to 2^512 calls</p> + <p> + This is a 58 bit version of Xoroshiro1024**, + from the 2018 paper by David Blackman and Sebastiano Vigna: + <url href="http://vigna.di.unimi.it/ftp/papers/ScrambledLinear.pdf"> + Scrambled Linear Pseudorandom Number Generators + </url> + that on a 64 bit Erlang system executes only about 30% slower than + the default <c>exrop</c> algorithm but with much longer period + and better statistical properties, and on the flip side + a larger state. + </p> + <p> + Many thanks to Sebastiano Vigna for his help with + the 58 bit adaption. + </p> + </item> <tag><c>exsp</c></tag> <item> <p>Xorshift116+, 58 bits precision and period of 2^116-1</p> @@ -195,8 +215,8 @@ SND0 = math:sqrt(-2 * math:log(R5)) * math:cos(math:pi() * R6)</pre> </note> <p> - For all these generators the lowest bit(s) has got - a slightly less random behaviour than all other bits. + For all these generators except <c>exro928ss</c> the lowest bit(s) + has got a slightly less random behaviour than all other bits. 1 bit for <c>exrop</c> (and <c>exsp</c>), and 3 bits for <c>exs1024s</c>. See for example the explanation in the @@ -254,11 +274,32 @@ tests. We suggest to use a sign test to extract a random Boolean value.</pre> </desc> </datatype> <datatype> - <name name="exs64_state"/> - <desc><p>Algorithm specific internal state</p></desc> + <name name="seed"/> + <desc> + <p> + A seed value for the generator. + </p> + <p> + A list of integers sets the generator's internal state directly, + after algorithm-dependent checks of the value + and masking to the proper word size. + </p> + <p> + An integer is used as the initial state for a SplitMix64 generator. + The output values of that is then used for setting + the generator's internal state + after masking to the proper word size + and if needed avoiding zero values. + </p> + <p> + A traditional 3-tuple of integers seed is passed through + algorithm-dependent hashing functions to create + the generator's initial state. + </p> + </desc> </datatype> <datatype> - <name name="exsplus_state"/> + <name name="exrop_state"/> <desc><p>Algorithm specific internal state</p></desc> </datatype> <datatype> @@ -266,7 +307,15 @@ tests. We suggest to use a sign test to extract a random Boolean value.</pre> <desc><p>Algorithm specific internal state</p></desc> </datatype> <datatype> - <name name="exrop_state"/> + <name name="exro928_state"/> + <desc><p>Algorithm specific internal state</p></desc> + </datatype> + <datatype> + <name name="exsplus_state"/> + <desc><p>Algorithm specific internal state</p></desc> + </datatype> + <datatype> + <name name="exs64_state"/> <desc><p>Algorithm specific internal state</p></desc> </datatype> </datatypes> |