From e324d29e2b5f78c3b38b293e19976205d6fcdb7d Mon Sep 17 00:00:00 2001 From: mrkn Date: Wed, 23 Mar 2016 12:41:00 +0000 Subject: * enum.c (ary_inject_op): Use Kahan's compensated summation algorithm for summing up float values. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54237 b2dd03c8-39d4-4d8f-98ff-823fe69b080e --- ChangeLog | 5 +++++ enum.c | 15 +++++++++++---- test/ruby/test_enum.rb | 7 +++++++ 3 files changed, 23 insertions(+), 4 deletions(-) diff --git a/ChangeLog b/ChangeLog index bf56c10b06..3dee449135 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +Wed Mar 23 21:38:00 2016 Kenta Murata + + * enum.c (ary_inject_op): Use Kahan's compensated summation algorithm + for summing up float values. + Wed Mar 23 20:56:59 2016 Nobuyoshi Nakada * strftime.c (rb_strftime_with_timespec): append formatted results diff --git a/enum.c b/enum.c index 3cef60c7ce..e6ca6ab0fc 100644 --- a/enum.c +++ b/enum.c @@ -634,7 +634,7 @@ ary_inject_op(VALUE ary, VALUE init, VALUE op) ID id; VALUE v, e; long i, n; - double f; + double f, c; if (RARRAY_LEN(ary) == 0) return init == Qundef ? Qnil : init; @@ -686,16 +686,23 @@ ary_inject_op(VALUE ary, VALUE init, VALUE op) rb_method_basic_definition_p(rb_cFloat, idPLUS)) { f = RFLOAT_VALUE(v); sum_float: + c = 0.0; while (1) { + double y, t; e = RARRAY_AREF(ary, i); if (RB_FLOAT_TYPE_P(e)) - f += RFLOAT_VALUE(e); + y = RFLOAT_VALUE(e) - c; else if (FIXNUM_P(e)) - f += FIX2LONG(e); + y = FIX2LONG(e) - c; else if (RB_TYPE_P(e, T_BIGNUM)) - f += rb_big2dbl(e); + y = rb_big2dbl(e) - c; else break; + + t = f + y; + c = (t - f) - y; + f = t; + i++; if (RARRAY_LEN(ary) <= i) return DBL2NUM(f); diff --git a/test/ruby/test_enum.rb b/test/ruby/test_enum.rb index 97730f919f..ba973e2d48 100644 --- a/test/ruby/test_enum.rb +++ b/test/ruby/test_enum.rb @@ -217,6 +217,13 @@ class TestEnumerable < Test::Unit::TestCase assert_float_equal(10.0, [3.0, 5].inject(2.0, :+)) assert_float_equal((FIXNUM_MAX+1).to_f, [0.0, FIXNUM_MAX+1].inject(:+)) assert_equal(2.0+3.0i, [2.0, 3.0i].inject(:+)) + + large_number = 100000000 + small_number = 1e-9 + until (large_number + small_number) == large_number + small_number /= 10 + end + assert_equal(large_number+(small_number*10), [large_number, *[small_number]*10].inject(:+)) end def test_inject_array_plus_redefined -- cgit v1.2.3