18.404/6.5400 Fall 2024
Introduction to the Theory of Computation

Subject Evaluation

Please take a few minutes to evaluate 18.404/6.5400. The deadline is Monday, December 16 at 9am.

If you've attended some recitations or office hours, your TAs (see below for names) would especially appreciate comments on their teaching. We read all comments about how to improve the course.

Information, Problem Sets, and Study Materials

** Access requires MIT certificates.

Homework submission instructions. Upload a single file with all non-optional problems to Gradescope by the due date. Handwritten is ok as long as we can read it easily, otherwise use latex. When Gradescope prompts you, mark the pages containing each problem. If you upload several files, the last upload file replaces all previous files, so upload the complete set. Do not upload individual problems separately.

Late homework submission. You may submit any individual problems after the due date, before 11:59pm the following day, for a 1 point per problem late penalty deduction. In each pset, you may submit some problems or problem parts on time and others late. (The penalty will be 10% of the part's point value.) At Noon on the due date, the regular Gradescope assignment for non-optional problems will close and a new "late submission" assignment will appear. Upload only those non-optional problems you wish to be counted as late, together in a single file. You may resubmit problems you submitted previously if you wish to change your answer, but these will be marked late and get the 1 point penalty. DO NOT RESUBMIT UNCHANGED PROBLEMS you submitted previously. The late submissions (even if unmarked) will override earlier submissions. Note: We cannot accept unexcused (see "Student Support" below) homework after the late submission deadline.

Optional problem submission. Submit the optional problems to a separate "optional problem" assignment. That assignment is configured to accept both on-time and late submissions. You will receive the usual 1 point penalty for a late optional problem. Optional problem parts may not be submitted separately for lateness consideration.

Regrade requests. If you feel that your work was incorrectly graded, you may submit a regrade request through Gradescope. Please review your graded papers promptly; regrade requests are accepted only for two weeks from the original pset due date. Please do not abuse the regrade system by making lots of frivolous requests; we have limited grader capacity.

If you need to communicate with us about the psets (e.g., medical extensions), email the grading team.

Resources

Course Staff

Special Review Sessions for the Final Exam

Office Hours

Lectures and Recitation Sections

Lectures are held in room 54-100 on Tuesdays and Thursdays from 2:30 to 4pm.
The one-hour recitations meet Fridays at the following times and rooms:

Recitation Notes

Notes are generally posted by the Tuesday following the Friday recitation.
  1. September 6 - Anna's notes - source
  2. September 13 - Sarah's notes - source
    September 20 - No classes (student holiday)
  3. September 27 - Leo G's notes - source
  4. October 4 - Zimi's notes - source
  5. October 11 - Leo Y's notes - source
  6. October 18 - Zed's notes - source
  7. October 25 - Anna's notes - source
  8. November 1 - Sarah's notes - source
  9. November 8 - Zed's notes - source
  10. November 15 - Jonathan's notes - source
  11. November 22 - Sean's notes - source
  12. December 6 - Nathan's notes - source

Course Schedule

  1. 9/5  Introduction, finite automata, regular expressions §1.1
  2. 9/10  Nondeterminism, closure properties, Reg Exprs → FA §1.2-1.3
  3. 9/12  Reg Exprs ← FA, Proving non-regularity via pumping lemma, CFGs §1.4-2.1
  4. 9/17  Context free languages, Pushdown Automata, CFG ⇆ PDA §2.2
  5. 9/19  Context-free pumping lemma, Turing machines §2.3,3.1 Pset 1 DUE (noon)
  6. 9/24  TM variants, Church-Turing thesis §3.2-3.3
  7. 9/26  Decision problems for automata and grammars §4.1
  8. 10/1  Undecidability §4.2
  9. 10/3  Reducibility §5.1,5.3 Pset 2 DUE (noon)
  10. 10/8  Computation history method §5.2
  11. 10/10  Recursion theorem, Logic §6.1-6.2
    10/15  NO CLASS --- Student Holiday
  12. 10/17  Time complexity §7.1 Pset 3 DUE (noon)
  13. 10/22  P and NP, SAT, Poly-time reducibility §7.2-7.3
  14. 10/24  Midterm Exam (during regular lecture time, in Walker)
  15. 10/29  NP-completeness §7.5
  16. 10/31  Cook-Levin theorem §7.4
  17. 11/5  Space complexity, PSPACE §8.1-8.2
  18. 11/7  Savitch's theorem, PSPACE-completeness §8.3 Pset 4 DUE (noon)
  19. 11/12  Games, Generalized geography, L and NL §8.3-8.4
  20. 11/14  NL-completeness, NL = coNL §8.4
  21. 11/19  Hierarchy theorems §9.1
  22. 11/21  Provably intractable problems, oracles §9.2 Pset 5 DUE (noon)
  23. 11/26  Probabilistic computation, BPP §10.2
    11/28  NO CLASS --- Thanksgiving
  24. 12/3  An interesting language in BPP, Arithmetization §10.2
  25. 12/5  Interactive proof systems, IP §10.4 Pset 6 DUE (noon)
  26. 12/10  coNP ⊆ IP §10.4

Midterm exam: Thursday, October 24, 2:30 - 4pm, Walker (Building 50), top floor.
Final exam: Monday, December 16, 1:30-4:30, DuPont Gym.

Student Support

If you are dealing with a personal or medical issue that may affect your participation in any MIT class, please discuss it with Student Support Services (S3) at 617-253-4861. Graduate students may contact GradSupport. We cannot excuse you from coursework without support from S3 or GradSupport.

For serious urgent matters at any time, every student may contact the 24x7 Dean on Call at (617) 253-1212.

If you may require disability accommodations, please speak early in the semester with Associate Dean Kathleen Monagle then let me know so that we can work together to get your accommodation logistics in place.

2020 Lectures

Required background. To succeed in this course, you need experience and skill with mathematical concepts, theorems, and proofs. If you did reasonably well in 18.062, 18.200, or any other substantial, proof-oriented mathematics subject, you should be fine. The course moves quickly, covering about 90% of the textbook. The problem sets generally require proving some statement, and creativity in finding proofs will be necessary.

Accessibility