Perhaps you have hit this bug... http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43434 My rough guess if you really care about speed splitting the task into multiple processes on multiple cores will win you way more than tweaking this loop. -- John Carter Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : john.carter@xxxxxxxxxxxxx New Zealand