File 2193-Update-after-feedback.patch of Package erlang

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File 2193-Update-after-feedback.patch of Package erlang (Revision 33fb1bfcfb3bce757d0f7cfc6a9a3eaf)

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From 877c714f5c46224447e8e362111ad1e25f4c12b9 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Thu, 31 Mar 2022 10:46:58 +0200
Subject: [PATCH 03/11] Update after feedback

* Rephrase some documentation
* Optimize with redundant masks to improve JIT
* Add more measure/1 benchmark items
---
 lib/stdlib/doc/src/rand.xml    |  6 +--
 lib/stdlib/src/rand.erl        | 17 +++++++--
 lib/stdlib/test/rand_SUITE.erl | 68 ++++++++++++++++++++++++++++++++--
 3 files changed, 82 insertions(+), 9 deletions(-)

diff --git a/lib/stdlib/doc/src/rand.xml b/lib/stdlib/doc/src/rand.xml
index 361692f33c..d45d0effca 100644
--- a/lib/stdlib/doc/src/rand.xml
+++ b/lib/stdlib/doc/src/rand.xml
@@ -912,7 +912,7 @@ end.</pre>
             few bits (under 35),
             is not a power of 2 generator (range 1 .. (2^35 - 32)),
             offers no help in generating numbers on a specified range,
-            etc...
+            and so on.
           </p>
           <p>
             But for pseudo random load distribution
@@ -974,8 +974,8 @@ end.</pre>
             But for pseudo random load distribution
             and such it might be useful, since it is extremely fast.
             The <seemfa marker="#mcg35/1"><c>mcg35/1</c></seemfa>
-            generator above has got less statistical artifacts,
-            but instead other pecularities since it is not
+            generator above has less statistical artifacts,
+            but instead it has other peculiarities since it is not
             a power of 2 generator.
           </p>
         </note>
diff --git a/lib/stdlib/src/rand.erl b/lib/stdlib/src/rand.erl
index d9ae09100e..d498bcdda5 100644
--- a/lib/stdlib/src/rand.erl
+++ b/lib/stdlib/src/rand.erl
@@ -1456,8 +1456,13 @@ dummy_seed({A1, A2, A3}) ->
 -type mcg35_state() :: 1..(?MCG35_M-1).
 
 -spec mcg35(X0 :: mcg35_state()) -> X1 :: mcg35_state().
-mcg35(X0) ->
-    X = ?MCG35_A * X0,
+mcg35(X0) -> % when is_integer(X0), 1 =< X0, X0 < ?MCG35_M ->
+    %% The mask operation on the input tricks the JIT into
+    %% realizing that all following operations does not
+    %% need bignum handling.  The suggested guard test above
+    %% could have had the same effect but it did not, and, alas,
+    %% needs much more native code to execute than a 'band'.
+    X = ?MCG35_A * ?MASK(?MCG35_B, X0),
     %% rem M = rem (2^B - D), optimization to avoid 'rem'
     X1 = ?MASK(?MCG35_B, X) + ?MCG35_D*(X bsr ?MCG35_B),
     if
@@ -1497,8 +1502,14 @@ mcg35(X0) ->
 -type lcg35_state() :: 0..?MASK(?LCG35_B).
 
 -spec lcg35(X0 :: lcg35_state()) -> X1 :: lcg35_state().
+%%lcg35(X0) when is_integer(X0), 0 =< X0, X0 =< ?MASK(?LCG35_B) ->
 lcg35(X0) ->
-    ?MASK(?LCG35_B, ?LCG35_A * X0 + ?LCG35_C).
+    %% The mask operation on the input tricks the JIT into
+    %% realizing that all following operations does not
+    %% need bignum handling.  The suggested guard test above
+    %% could have had the same effect but it did not, and, alas,
+    %% needs much more native code to execute than a 'band'.
+    ?MASK(?LCG35_B, ?LCG35_A * ?MASK(?LCG35_B, X0) + ?LCG35_C).
 
 
 %% =====================================================================
diff --git a/lib/stdlib/test/rand_SUITE.erl b/lib/stdlib/test/rand_SUITE.erl
index 9eed862a66..0c82076422 100644
--- a/lib/stdlib/test/rand_SUITE.erl
+++ b/lib/stdlib/test/rand_SUITE.erl
@@ -1184,6 +1184,22 @@ do_measure(_Config) ->
                     State)
           end,
           unique_phash2, TMarkUniformRange10000, OverheadUniformRange1000),
+    _ =
+        measure_1(
+          fun (_) -> 10000 end,
+          fun (State, Range, _) ->
+                  measure_loop(
+                    fun (State0) ->
+                            %% Just a 'rem' with slightly skewed distribution
+                            case os:system_time(microsecond) rem Range of
+                                R
+                                  when is_integer(R), 0 =< R, R < Range ->
+                                    State0
+                            end
+                    end,
+                    State)
+          end,
+          system_time_rem, TMarkUniformRange10000, OverheadUniformRange1000),
     %%
     ct:pal("~nRNG uniform integer 32 bit performance~n",[]),
     [TMarkUniform32Bit,OverheadUniform32Bit|_] =
@@ -1245,6 +1261,24 @@ do_measure(_Config) ->
                     State)
           end,
           unique_phash2, TMarkUniform32Bit, OverheadUniform32Bit),
+    _ =
+        measure_1(
+          fun (_) -> 1 bsl 32 end,
+          fun (State, Range, _) ->
+                  measure_loop(
+                    fun (State0) ->
+                            case
+                                os:system_time(microsecond)
+                                band ((1 bsl 32) - 1)
+                            of
+                                R
+                                  when is_integer(R), 0 =< R, R < Range ->
+                                    State0
+                            end
+                    end,
+                    State)
+          end,
+          system_time_rem, TMarkUniform32Bit, OverheadUniform32Bit),
     %%
     ct:pal("~nRNG uniform integer half range performance~n",[]),
     _ =
@@ -1365,7 +1399,10 @@ do_measure(_Config) ->
           unique_phash2, TMarkUniformFullRange, OverheadUniformFullRange),
     _ =
         measure_1(
-          fun (State) -> half_range(State) bsl 1 end,
+          fun (State) ->
+                  rand:seed(State),
+                  half_range(State) bsl 1
+          end,
           fun (State, Range, Mod) ->
                   measure_loop(
                     fun (St) ->
@@ -1377,6 +1414,26 @@ do_measure(_Config) ->
                     State)
           end,
           procdict, TMarkUniformFullRange, OverheadUniformFullRange),
+    _ =
+        measure_1(
+          fun (State) ->
+                  _ = put(lcg35_procdict, State),
+                  1 bsl 35
+          end,
+          fun (State, Range, _) ->
+                  measure_loop(
+                    fun (State0) ->
+                            case
+                                put(lcg35_procdict,
+                                    rand:lcg35(get(lcg35_procdict)))
+                            of
+                                R when is_integer(R), 0 =< R, R < Range ->
+                                    State0
+                            end
+                    end,
+                    State)
+          end,
+          lcg35_procdict, TMarkUniformFullRange, OverheadUniformFullRange),
     %%
     ct:pal("~nRNG uniform integer full range + 1 performance~n",[]),
     _ =
@@ -1629,23 +1686,28 @@ measure_1(RangeFun, Fun, Alg, TMark, Overhead) ->
                 {?MODULE, <<>>};
             unique_phash2 ->
                 {?MODULE, ignored_state};
+            system_time_rem ->
+                {?MODULE, ignored_state};
             mcg35_inline ->
                 {_, S} = rand:seed_s(dummy),
                 {?MODULE, (S rem ((1 bsl 35)-31 - 1)) + 1};
             lcg35_inline ->
                 {_, S} = rand:seed_s(dummy),
                 {?MODULE, S bsr (58-35)};
+            lcg35_procdict ->
+                {_, S} = rand:seed_s(dummy),
+                {?MODULE, S bsr (58-35)};
             exsp_inline ->
                 {_, S} = rand:seed_s(exsp),
                 {?MODULE, S};
             procdict ->
-                {rand, rand:seed(exsss)};
+                {rand, rand:seed_s(exsss)};
             _ ->
                 {rand, rand:seed_s(Alg)}
         end,
-    Range = RangeFun(State),
     Pid = spawn_link(
             fun() ->
+                    Range = RangeFun(State),
                     {T, ok} = timer:tc(fun () -> Fun(State, Range, Mod) end),
                     Time = T - Overhead,
                     Percent =
-- 
2.34.1

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File 2193-Update-after-feedback.patch of Package erlang (Revision 33fb1bfcfb3bce757d0f7cfc6a9a3eaf)

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