File 2954-Change-mwc59-multiplier.patch of Package erlang

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File 2954-Change-mwc59-multiplier.patch of Package erlang (Revision 391c6b6c651eed25824a4cd58b48efbd)

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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>
 
 
 This generator uses the multiplier 2^32 and the modulus
- 16#7f17555&nbsp;*&nbsp;2^32&nbsp;-&nbsp;1,
+ 16#7fa6502&nbsp;*&nbsp;2^32&nbsp;-&nbsp;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: 
 <c>C&nbsp;=&nbsp;<anno>CX0</anno>&nbsp;bsr&nbsp;32</c> 
 <c>X&nbsp;=&nbsp;<anno>CX0</anno>&nbsp;band&nbsp;((1&nbsp;bsl&nbsp;32)-1))</c> 
- <c><anno>CX1</anno>&nbsp;=&nbsp;16#7f17555&nbsp;*&nbsp;X&nbsp;+&nbsp;C</c>
+ <c><anno>CX1</anno>&nbsp;=&nbsp;16#7fa6502&nbsp;*&nbsp;X&nbsp;+&nbsp;C</c>
 
 
 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

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File 2954-Change-mwc59-multiplier.patch of Package erlang (Revision 391c6b6c651eed25824a4cd58b48efbd)

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