File 5694-Change-mwc59-multiplier.patch of Package erlang
From 7e9261cae537c1824373848512d279c0e9245cd2 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Tue, 3 May 2022 14:44:42 +0200
Subject: [PATCH 4/6] Change `mwc59` multiplier
---
lib/stdlib/doc/src/rand.xml | 6 +++---
lib/stdlib/src/rand.erl | 13 +++++--------
lib/stdlib/test/rand_SUITE.erl | 12 ++++++------
3 files changed, 14 insertions(+), 17 deletions(-)
diff --git a/lib/stdlib/doc/src/rand.xml b/lib/stdlib/doc/src/rand.xml
index 22135d3443..839c6c0ce5 100644
--- a/lib/stdlib/doc/src/rand.xml
+++ b/lib/stdlib/doc/src/rand.xml
@@ -898,7 +898,7 @@ end.</pre>
</p>
<p>
This generator uses the multiplier 2^32 and the modulus
- 16#7f17555 * 2^32 - 1,
+ 16#7fa6502 * 2^32 - 1,
which have been selected,
in collaboration with Sebastiano Vigna,
to avoid bignum operations
@@ -906,7 +906,7 @@ end.</pre>
It can be written as:<br/>
<c>C = <anno>CX0</anno> bsr 32</c><br/>
<c>X = <anno>CX0</anno> band ((1 bsl 32)-1))</c><br/>
- <c><anno>CX1</anno> = 16#7f17555 * X + C</c>
+ <c><anno>CX1</anno> = 16#7fa6502 * X + C</c>
</p>
<p>
The quality of the generated bits is best in the low end;
@@ -946,7 +946,7 @@ end.</pre>
than the default generator, which in itself
is a quality concern, although when used with the
value scramblers it passes strict PRNG tests
- (TestU01 BigCrush and PractRand 2 TB).
+ (most of TestU01 BigCrush and PractRand 2 TB).
The generator is significantly faster than
<seemfa marker="#exsp_next/1"><c>exsp_next/1</c></seemfa>
but with a bit lower quality.
diff --git a/lib/stdlib/src/rand.erl b/lib/stdlib/src/rand.erl
index 5f94804bfb..47766f2547 100644
--- a/lib/stdlib/src/rand.erl
+++ b/lib/stdlib/src/rand.erl
@@ -1476,9 +1476,9 @@ dummy_seed({A1, A2, A3}) ->
%% and a double Xorshift to get all bits good enough.
%%
%% The chosen parameters are:
-%% A = 16#7f17555
+%% A = 16#7fa6502
%% B = 32
-%% Single Xorshift: 10
+%% Single Xorshift: 16
%% Double Xorshift: 8, 16
%%
%% These parameters gives the MWC "digit" size 32 bits
@@ -1493,17 +1493,14 @@ dummy_seed({A1, A2, A3}) ->
%%% -define(MWC_A, (6)).
%%% -define(MWC_B, (3)).
-%%% -define(MWC59_A, (16#20075dc0)).
-%%% -define(MWC59_A, (16#1ffb0729)).
+%%% -define(MWC59_A, (16#20075dc0)). % 16#1ffb0729
%%% -define(MWC59_B, (29)).
-%%% -define(MWC59_A, (16#7fa6502)).
--define(MWC59_A, (16#7f17555)).
-%%% -define(MWC59_A, (16#3f35301)).
+-define(MWC59_A, (16#7fa6502)). % 16#7f17555 16#3f35301
-define(MWC59_B, (32)).
-define(MWC59_P, ((?MWC59_A bsl ?MWC59_B) - 1)).
--define(MWC59_XS, 10).
+-define(MWC59_XS, 16).
-define(MWC59_XS1, 8).
-define(MWC59_XS2, 16).
diff --git a/lib/stdlib/test/rand_SUITE.erl b/lib/stdlib/test/rand_SUITE.erl
index 90ea2890e8..eabb9396ad 100644
--- a/lib/stdlib/test/rand_SUITE.erl
+++ b/lib/stdlib/test/rand_SUITE.erl
@@ -214,20 +214,20 @@ mwc59_api(Config) when is_list(Config) ->
mwc59_api(1, 1000000).
mwc59_api(CX0, 0) ->
- CX = 298134347579367847,
+ CX = 216355295181821136,
{CX, CX} = {CX0, CX},
V0 = rand:mwc59_value(CX0),
- V = 44296811804442023,
+ V = 215617979550160080,
{V, V} = {V0, V},
W0 = rand:mwc59_full_value(CX0),
- W = 43477957222139559,
+ W = 70209996550472912,
{W, W} = {W0, W},
F0 = rand:mwc59_float(CX0),
F = (W band ((1 bsl 53) - 1)) * (1 / (1 bsl 53)),
{F, F} = {F0, F},
ok;
mwc59_api(CX, N)
- when is_integer(CX), 1 =< CX, CX < (16#7f17555 bsl 32) - 1 ->
+ when is_integer(CX), 1 =< CX, CX < (16#7fa6502 bsl 32) - 1 ->
V = rand:mwc59_value(CX),
W = rand:mwc59_full_value(CX),
F = rand:mwc59_float(CX),
@@ -1354,7 +1354,7 @@ do_measure(Iterations) ->
_ =
measure_1(
fun (_Mod, _State) ->
- Range = (16#7f17555 bsl 32) - 1,
+ Range = (16#7fa6502 bsl 32) - 1,
fun (St0) ->
St1 = rand:mwc59(St0),
V = St1,
@@ -1455,7 +1455,7 @@ do_measure(Iterations) ->
_ =
measure_1(
fun (_Mod, _State) ->
- Range = (16#7f17555 bsl 32) - 1,
+ Range = (16#7fa6502 bsl 32) - 1,
fun (St0) ->
case
put(mwc59_procdict,
--
2.35.3
