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 --- enum.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'enum.c') 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); -- cgit v1.2.3