diff options
Diffstat (limited to 'enum.c')
-rw-r--r-- | enum.c | 17 |
1 files changed, 11 insertions, 6 deletions
@@ -3644,8 +3644,11 @@ sum_iter(VALUE i, struct enum_sum_memo *memo) } } else if (RB_FLOAT_TYPE_P(v)) { - /* Kahan's compensated summation algorithm */ - double x, y, t; + /* + * Kahan-Babuska balancing compensated summation algorithm + * See http://link.springer.com/article/10.1007/s00607-005-0139-x + */ + double x, t; float_value: if (RB_FLOAT_TYPE_P(i)) @@ -3662,9 +3665,11 @@ sum_iter(VALUE i, struct enum_sum_memo *memo) goto some_value; } - y = x - c; - t = f + y; - c = (t - f) - y; + t = f + x; + if (fabs(f) >= fabs(x)) + c += ((f - t) + x); + else + c += ((x - t) + f); f = t; } else { @@ -3788,7 +3793,7 @@ enum_sum(int argc, VALUE* argv, VALUE obj) rb_block_call(obj, id_each, 0, 0, enum_sum_i, (VALUE)&memo); if (memo.float_value) { - return DBL2NUM(memo.f); + return DBL2NUM(memo.f + memo.c); } else { if (memo.n != 0) |