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