Grading with partial score
Sometimes a problem does not need to be solved perfectly. The user may have too little time to think about every possible testcase, the problem may be so hard that even passing some tests is quite an achievement, or sometimes one does not want to discourage users by showing them just a plain "wrong answer" message. It all of these cases, a partial score judge may be used. The author is still able to verify the programmer's skills, but now he or she may do it more precisely: having two users with "wrong answer" says less than having one with a score of 50% and one with a score of 75%.