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authorGuilherme Andrade <[email protected]>2017-03-22 22:15:15 +0000
committerGuilherme Andrade <[email protected]>2017-03-22 22:15:15 +0000
commitc84e541b78cb9ee63a02db2240903ddd6131793a (patch)
tree245382e7310e5bcbec9a98a0aa3b7b4b7dc4b008 /lib/crypto/src
parentec1e5bc7ff8101b7db4fa5d67bbbed652a9238c8 (diff)
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Attempt faster approach to strong random floats
Diffstat (limited to 'lib/crypto/src')
-rw-r--r--lib/crypto/src/crypto.erl13
1 files changed, 5 insertions, 8 deletions
diff --git a/lib/crypto/src/crypto.erl b/lib/crypto/src/crypto.erl
index 777b5cd1c6..d8bc13b537 100644
--- a/lib/crypto/src/crypto.erl
+++ b/lib/crypto/src/crypto.erl
@@ -49,6 +49,9 @@
%% This should correspond to the similar macro in crypto.c
-define(MAX_BYTES_TO_NIF, 20000). %% Current value is: erlang:system_info(context_reductions) * 10
+%% Used by strong_rand_float/0
+-define(HALF_DBL_EPSILON, 1.1102230246251565e-16). % math:pow(2, -53)
+
%%-type ecdsa_digest_type() :: 'md5' | 'sha' | 'sha256' | 'sha384' | 'sha512'.
-type crypto_integer() :: binary() | integer().
%%-type ec_named_curve() :: atom().
@@ -342,14 +345,8 @@ strong_rand_range(BinRange) when is_binary(BinRange) ->
strong_rand_range_nif(_BinRange) -> ?nif_stub.
strong_rand_float() ->
- % This could be optimized by having its own NIF
- Sign = 0, % positive
- Exponent = 1023, % on the interval [1.0, 2.0[
- BinFraction = strong_rand_range(1 bsl 52), % the whole interval above
- Fraction = bin_to_int(BinFraction),
- <<Value:64/big-float>> = <<Sign:1, Exponent:11, Fraction:52>>,
- Value - 1.0.
-
+ WholeRange = strong_rand_range(1 bsl 53),
+ ?HALF_DBL_EPSILON * bytes_to_integer(WholeRange).
rand_uniform(From,To) when is_binary(From), is_binary(To) ->
case rand_uniform_nif(From,To) of