CS536: Science of Programming, Fall 2023

• Section 01: In-person class
• Section 02: In-person class, PhD qualifier section
• Section 03: Online

Course Outcomes

By the end of the class, you should be able to answer:

• How does verification differ from testing?
• How do we understand the semantics of programs?
• How do semantics affect the way we understand program correctness?
• What rules of reasoning can we use to discuss program correctness?
• How is correctness of parallel programs different?
• What if program execution isn't deterministic?

Prerequisites: CS330 and CS331

Schedule

Note: this schedule is incomplete, tentative and subject to change.

		Topic	Notes
Aug.	21	Intro	Slides
	23	Propositional logic	Slides	Practice	HW1 Out
	28	Pred. logic, State update and substitution	Notes	Practice
	30	Expressions and types	Notes	Practice
Sep.	4	No class - Labor Day
	6	Statements and operational semantics	Notes	Practice	HW1 Due
	11	Big-step semantics, divergence, runtime errors	Notes	Practice	HW2 Out
	13	Hoare triples I	Notes	Practice
	18	Hoare triples II	(cont'd)	Practice
	20	Hoare triples III	Notes		HW2 Due
	25	Proofs and Proof Outlines	Notes	Practice
	27	Weakest preconditions I	Notes	Practice
Oct.	2	Weakest preconditions II	Notes	Practice
	4	Strongest postconditions	Notes	Practice
	9	No class - Fall break
	11	Loop invariants I	Notes	Practice
	16	Loop invariants II	(Cont'd)	Practice
	18	Review session
	23	Midterm Exam
	25	Proof Outlines	Notes	Practice	HW5 Out
	30	Loop bounds	Notes	Practice
Nov.	1	Array Assignments	Notes	Practice
	6	Pointers and local reasoning	Notes		HW5 Due
	8	Separation logic	Notes		HW6 Out
	13	Separation logic	(cont'd)
	15	Sequential nondeterminism	Notes	Practice
	20	Parallel program basics	Notes	Practice	HW6 Due, HW7 Out
	22	No class - Thanksgiving break
	27	Class cancelled
	29	Concurrent separation logic/Wrap-up	Slides		HW7 Due
Dec.	5	Final Exam - 2-4pm

Resources

Textbook:

There is no required textbook for the course. Class notes will be provided.

If you really want a book to reference, the following are OK but entirely optional (list and notes courtesy of Jim Sasaki):

• The Science of Programming, by David Gries, Springer-Verlag, © 1981. Unfortunately the book uses weird notation and has a number of typographical errors and doesn't include everything we'll be covering.
• Most of the course material comes from Verification of Sequential and Concurrent Programs (3rd edition), by Krzysztof R. Apt, Frank S. de Boer, and Ernst-Rüdiger Olderog, © 2009, Springer-Verlag. But don't get this book: It's expensive and written for a very theoretical audience.

Also, here are some potentially helpful references for reviewing propositional and predicate logic (these are very important topics for understanding the course material; they will be reviewed briefly the first week of class but it is mostly assumed you already have some logic background; again this list is courtesy of Jim Sasaki):

1. One reference is online at myIIT Library > Databases > Books 24x7. Search for Fundamentals of Discrete Math for Computer Science: A Problem-Solving Primer by Tom Jenkyns and Ben Stephenson, Springer © 2013.  Study Sections 3.2 (Boolean Expressions and Truth Tables) and 3.3 (Predicates and Quantifiers).
2. There is a CodeGuage site with an Elementary Logic course. A quick spin through that might be helpful. Unfortunately, it seems they only discuss predicates with outermost quantifiers. (E.g., ∃x.∃y.p, but not predicates like (∃x.p) → (∃y.q).)
3. There's a handout at Cornell that is a more detailed introduction to predicate calculus. Two notes: We write (e.g.) (∀x.P) ∧ ∃y.Q where they write (∀x)(P ∧ (∃y)Q). We write logical equivalence as "⇔"; they use

   LE

   ↔

   .
Other Resources:

Logic proof checker

Dafny installation instructions

Dafny documentation

Policies

Attendance

Sections 01 and 02 will meet on campus. Live attendance is encouraged; the ability to hear the material and ask questions live is valuable, and while participation is not an explicit part of your grade, it may be used to "break ties." That said, attendance is not mandatory, and the occasional absence will not count against you and doesn't need to be excused. If you are in Sections 01 and 02 and are consistently not able to come to lecture for some reason, discuss this with the instructor. I do not currently plan to livestream lectures, but they will be recorded.

Section 03 is an online section; you will watch the lectures online at your leisure but complete the same assignments and exams as the in-person students. For classroom capacity reasons, Section 03 students should not attend in-person without the permission of the instructor.

PhD Qualifier section

PhD students who wish to use this course to satisfy the written qualifying requirement must be enrolled in Section 02 (even if you are not able to attend class in person; please let me know if this is the case, but I won't hold it against you). Students in this section will complete the same assignments and exams as the other sections, but may be graded to a different standard.

Grading

Final grades will be based on the following:

40%	Homeworks (6-8, may not be evenly weighted)
25%	Midterm Exam (Oct. 23)
35%	Final Exam

Final letter grades will be calculated as follows:


>=85	A
70-85	B
60-70	C
<60	E

My main grading policy is fairness: asking for a higher grade (without pointing to specific things that have been graded incorrectly) won't succeed, because that wouldn't be fair to the rest of the students. I understand that this is a required class for many students and there may be unpleasant consequences for earning less than a certain grade, however that absolutely cannot be a factor in your grade.

Late Days/Late Work

Each student has 8 "late days" to use on homeworks over the course of the semester. Using a late day extends the deadline by 24 hours. You do not need to let us know you're using late days; they'll be deducted automatically when you hand in the work.

Important: No more than two late days may be used on any one assignment. Late days may not be used on exams.

After 48 hours, late work will not be accepted without the instructor's permission (and will be granted only for good reasons, e.g., medical emergencies).

If you've used up your late days, work up to 2 days late (without prior permission from the instructor) will be accepted with a penalty of 10% per day.

Exams

Section 01 and 02 students will take the midterm exam in person at the normal class time. Section 03 students should expect an email to make arrangements to take the exam. If they can take the exam in class, this is preferred, but arrangements for remote exams are also possible. The final exam will be during finals week at a time to be determined by the Registrar. More details will be announced later.

Collaboration and Using Outside Sources

All work submitted for credit (homework and exams) must be your own individual work. Some examples of violations of this policy are sharing answers with other students (this is a violation for all students involved, even if the answers were the original work of one of the students), looking up answers to questions on the web, and using generative AI tools like ChatGPT^* (note that these are just some examples, but not an exhaustive list).

One exception is that you are free to get help from the instructor, TAs, and Illinois Tech's Academic Resource Center. These resources are here for you, and you can (and should!) use them if you need to. If you are working with a tutor outside of Illinois Tech or have a similar situation, please discuss the situation with the instructor as soon as possible and before submitting any work.

All violations of this policy will result in a zero on the relevant assignment or exam, and a report to the university's academic honesty office (which may result in additional penalties with repeated violations). For more information about what constitutes academic dishonesty and the policies we are required to follow if we discover dishonesty, please view the university's Code of Academic Honesty.

If you're ever in doubt about whether something would violate the policy, don't hesitate to contact the instructor or TA. It's always better to ask and be sure.

^*Why can't I use ChatGPT? I feel the need to explain this particular rule in more detail. Generative AI tools are likely to be with us for the long run and if you use what you learn in CS536 after the semester is over (and I hope you will!) you might well use such tools to assist with some of the more tedious parts, so you might well wonder why you can't use them during the class. The short(-ish) answer is that ChatGPT is a language model. Sophisticated as it may be, it has no model of formal logic, a necessary component of producing formal proofs. Without a background in logic and proof methods, which you'll be learning in this class, you have no way of knowing if a proof from an outside source is correct, mostly correct, or entirely wrong. While this is a graduate-level class, you are learning the basics of a new set of skills, and when learning a new skill, it's important to learn to do it yourself so that you have the skills to understand and sanity-check answers that, when you're more advanced, you might be able to get with the assistance of a tool. Think of it like when you were first learning arithmetic and had to do so without a calculator. The rule was frustrating for us all then, and I expect this rule will cause some frustration now, but it's necessary for learning the basics of a new set of skills.

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Disability Accommodations

Reasonable accommodations will be made for students with documented disabilities. To obtain a letter of accommodation, contact the Center for Disability Resources at https://www.iit.edu/cdr.