Lecture: SAT & SMT, Part 1

Date: 1/23/17

Reading

• Required reading: How to read a research paper, Michael Mitzenmacher, online, 2002.
• Required reading: The Verifying Compiler: A Grand Challenge for Computing Research, Tony Hoare, Journal of the ACM, Vol. 50, No. 1, 2003.

No summaries are necessary for this class.

Preparation

Install Z3. Download the latest release 4.5.0 from https://github.com/Z3Prover/z3/releases.

Make sure the Python binding works. You may need to add the path to Z3’s bin directory to the environment variable PYTHONPATH.

$ python
Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from z3 import *
>>> x = Int('x')
>>> prove(x < x + 1)
proved
>>> 

Class notes

• Administrative
  • Class structure reminder
  • First assignment due this Friday. Turn in via Blackboard.
    • Too easy? Challenge problems too hard? Can be the basis for a project if so
    • Use Piazza for questions
• Tools
  • Dafny
  • Coq
  • Lean
  • TLA+
  • F*
  • Rosette
  • Isabelle/HOL
  • Other interactive provers: ACL2, Twelf, PVS
• How to read a research paper
  • Not reading a textbook. Be skeptical! But also look for good insights you can use.
  • Interact with the paper!
    • Highlighter + red pen
• The Verifying Compiler: A Grand Challenge for Computing Research
  • Clear measure of success
  • Research oriented: Industry very good at incremental advances
  • Updates to the list of challenges he mentions
  • Note the difference between a verified compiler and a verifying compiler
    • We will read CompCert paper
    • You can try out VCC
    • Are we done?
  • How important is verification of legacy code?
  • Note reference to tremendous improvement in SAT solving
  • Note repeated references to desire for trustworthy/secure software
• SAT/SMT: Why start here?
  • Very successful
  • Can be used for lots of things, not just verification
  • Supports automation, which I’m a big fan of
• Z3 64-bit encoding example
  • Original C version le16.c, le64.c
  • Z3 interpretation le16.py, le64.c