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random: Add description to the jumping methods of Xoshiro256StarStar #1991

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Merged
merged 2 commits into from
Nov 16, 2022
Merged

random: Add description to the jumping methods of Xoshiro256StarStar #1991

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458f787
random: Add description to the jumping methods of Xoshiro256StarStar
TimWolla Nov 10, 2022
191c0c0
random: Improve explanation of Xoshiro jumping
TimWolla Nov 15, 2022
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20 changes: 16 additions & 4 deletions reference/random/random/engine/xoshiro256starstar/jump.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,17 @@
<void />
</methodsynopsis>
<para>

Moves the algorithm’s state ahead by 2<superscript>128</superscript> steps, as if
<function>Random\Engine\Xoshiro256StarStar::generate</function> was called
2<superscript>128</superscript> times.
</para>
<para>
The purpose of a jump is to facilitate the creation of a new <classname>Random\Engine\Xoshiro256StarStar</classname>
engine from an existing seeded <classname>Random\Engine\Xoshiro256StarStar</classname> engine.
The seeded engine acts as a blueprint, which can be <link linkend="language.oop5.cloning">cloned</link>
and repeatedly jumped to create 2<superscript>128</superscript> non-overlapping sequences with
2<superscript>128</superscript> values each.
</para>

&warn.undocumented.func;

</refsect1>

<refsect1 role="parameters">
Expand Down Expand Up @@ -53,6 +59,12 @@
</example>
</refsect1>

<refsect1 role="seealso">
&reftitle.seealso;
<simplelist>
<member><function>Random\Engine\Xoshiro256StarStar::jumpLong</function></member>
</simplelist>
</refsect1>

</refentry>
<!-- Keep this comment at the end of the file
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25 changes: 21 additions & 4 deletions reference/random/random/engine/xoshiro256starstar/jumplong.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -12,11 +12,22 @@
<void />
</methodsynopsis>
<para>

Moves the algorithm’s state ahead by 2<superscript>192</superscript> steps, as if
<function>Random\Engine\Xoshiro256StarStar::generate</function> was called
2<superscript>192</superscript> times.
</para>
<para>
The purpose of a long jump is to facilitate the creation of a new <classname>Random\Engine\Xoshiro256StarStar</classname>
engine from an existing seeded <classname>Random\Engine\Xoshiro256StarStar</classname> engine.
The seeded engine acts as a blueprint, which can be <link linkend="language.oop5.cloning">cloned</link>
and repeatedly jumped to create 2<superscript>64</superscript> non-overlapping sequences with
2<superscript>192</superscript> values each.
</para>
<para>
Long jumping may be combined with <function>Random\Engine\Xoshiro256StarStar::jump</function>ing
to further split each of the 2<superscript>64</superscript> sequences generated by long jumping,
into 2<superscript>128</superscript> sequences of 2<superscript>64</superscript> values each.
</para>

&warn.undocumented.func;

</refsect1>

<refsect1 role="parameters">
Expand Down Expand Up @@ -53,6 +64,12 @@
</example>
</refsect1>

<refsect1 role="seealso">
&reftitle.seealso;
<simplelist>
<member><function>Random\Engine\Xoshiro256StarStar::jump</function></member>
</simplelist>
</refsect1>

</refentry>
<!-- Keep this comment at the end of the file
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