The implementation is then run against a test suite to check its correctness. Since this part of problem set grading is run automatically, it is vital that students submit their implementations in the form expected by the 6.170 autograder. This allows students to make sure their code is in the right place, includes all the required files, and basically works. This program packages the student's implementation for submission.
Students can run it as often as they wish until the problem set is due.
When the problem set is due, the TAs will run a program that fetches all the students' implementations. This program allows students to resubmit their implementation. If a student's implementation fails the TA test suite, the student can fix the code and resubmit a certain number of times without penalty. The student receives an email with the result of the resubmission. See the General Information handout for details about the requirements for, and rewards from, using returnin.