diff options
Diffstat (limited to 'lib/stdlib/src/random.erl')
| -rw-r--r-- | lib/stdlib/src/random.erl | 66 |
1 files changed, 42 insertions, 24 deletions
diff --git a/lib/stdlib/src/random.erl b/lib/stdlib/src/random.erl index 01227c29b4..d7b51a151c 100644 --- a/lib/stdlib/src/random.erl +++ b/lib/stdlib/src/random.erl @@ -1,7 +1,7 @@ %% %% %CopyrightBegin% %% -%% Copyright Ericsson AB 1996-2009. All Rights Reserved. +%% Copyright Ericsson AB 1996-2011. All Rights Reserved. %% %% The contents of this file are subject to the Erlang Public License, %% Version 1.1, (the "License"); you may not use this file except in @@ -26,6 +26,10 @@ -export([seed/0, seed/1, seed/3, uniform/0, uniform/1, uniform_s/1, uniform_s/2, seed0/0]). +-define(PRIME1, 30269). +-define(PRIME2, 30307). +-define(PRIME3, 30323). + %%----------------------------------------------------------------------- %% The type of the state @@ -44,12 +48,19 @@ seed0() -> -spec seed() -> ran(). seed() -> - reseed(seed0()). + case seed_put(seed0()) of + undefined -> seed0(); + {_,_,_} = Tuple -> Tuple + end. + %% seed({A1, A2, A3}) %% Seed random number generation --spec seed({integer(), integer(), integer()}) -> 'undefined' | ran(). +-spec seed({A1, A2, A3}) -> 'undefined' | ran() when + A1 :: integer(), + A2 :: integer(), + A3 :: integer(). seed({A1, A2, A3}) -> seed(A1, A2, A3). @@ -57,20 +68,21 @@ seed({A1, A2, A3}) -> %% seed(A1, A2, A3) %% Seed random number generation --spec seed(integer(), integer(), integer()) -> 'undefined' | ran(). +-spec seed(A1, A2, A3) -> 'undefined' | ran() when + A1 :: integer(), + A2 :: integer(), + A3 :: integer(). seed(A1, A2, A3) -> - put(random_seed, - {abs(A1) rem 30269, abs(A2) rem 30307, abs(A3) rem 30323}). + seed_put({(abs(A1) rem (?PRIME1-1)) + 1, % Avoid seed numbers that are + (abs(A2) rem (?PRIME2-1)) + 1, % even divisors of the + (abs(A3) rem (?PRIME3-1)) + 1}). % corresponding primes. --spec reseed(ran()) -> ran(). - -reseed({A1, A2, A3}) -> - case seed(A1, A2, A3) of - undefined -> seed0(); - {_,_,_} = Tuple -> Tuple - end. +-spec seed_put(ran()) -> 'undefined' | ran(). + +seed_put(Seed) -> + put(random_seed, Seed). %% uniform() %% Returns a random float between 0 and 1. @@ -82,18 +94,19 @@ uniform() -> undefined -> seed0(); Tuple -> Tuple end, - B1 = (A1*171) rem 30269, - B2 = (A2*172) rem 30307, - B3 = (A3*170) rem 30323, + B1 = (A1*171) rem ?PRIME1, + B2 = (A2*172) rem ?PRIME2, + B3 = (A3*170) rem ?PRIME3, put(random_seed, {B1,B2,B3}), - R = A1/30269 + A2/30307 + A3/30323, + R = B1/?PRIME1 + B2/?PRIME2 + B3/?PRIME3, R - trunc(R). %% uniform(N) -> I %% Given an integer N >= 1, uniform(N) returns a random integer %% between 1 and N. --spec uniform(pos_integer()) -> pos_integer(). +-spec uniform(N) -> pos_integer() when + N :: pos_integer(). uniform(N) when is_integer(N), N >= 1 -> trunc(uniform() * N) + 1. @@ -104,20 +117,25 @@ uniform(N) when is_integer(N), N >= 1 -> %% uniform_s(State) -> {F, NewState} %% Returns a random float between 0 and 1. --spec uniform_s(ran()) -> {float(), ran()}. +-spec uniform_s(State0) -> {float(), State1} when + State0 :: ran(), + State1 :: ran(). uniform_s({A1, A2, A3}) -> - B1 = (A1*171) rem 30269, - B2 = (A2*172) rem 30307, - B3 = (A3*170) rem 30323, - R = A1/30269 + A2/30307 + A3/30323, + B1 = (A1*171) rem ?PRIME1, + B2 = (A2*172) rem ?PRIME2, + B3 = (A3*170) rem ?PRIME3, + R = B1/?PRIME1 + B2/?PRIME2 + B3/?PRIME3, {R - trunc(R), {B1,B2,B3}}. %% uniform_s(N, State) -> {I, NewState} %% Given an integer N >= 1, uniform(N) returns a random integer %% between 1 and N. --spec uniform_s(pos_integer(), ran()) -> {integer(), ran()}. +-spec uniform_s(N, State0) -> {integer(), State1} when + N :: pos_integer(), + State0 :: ran(), + State1 :: ran(). uniform_s(N, State0) when is_integer(N), N >= 1 -> {F, State1} = uniform_s(State0), |