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* 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
This commit is contained in:
mrkn 2016-03-23 12:41:00 +00:00
parent 5396d8a1ab
commit e324d29e2b
3 changed files with 23 additions and 4 deletions
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5
ChangeLog
View File

@ -1,3 +1,8 @@
Wed Mar 23 21:38:00 2016 Kenta Murata <mrkn@mrkn.jp>
* 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 <nobu@ruby-lang.org>
* strftime.c (rb_strftime_with_timespec): append formatted results

15
enum.c
View File

@ -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);

7
test/ruby/test_enum.rb
View File

@ -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