Complexity
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Contents |
Resources
- Complexity Theory, by Arora and Barak
- The Complexity Zoo (invaluable reference page for definitions of classes)
Course Outline
- Why P-time (TMs, invariance of machine models, basic hierarchy theorems) (Chapter 1)
- Trust but verify (nondeterminism): non-d space. Savitch's theorem, non-d time, Cook's theorem, Reductions
- Let's play a game: PSPACE, QBF, ptime-hierarchy in terms of alternating TMs ?
- Can someone please prove a lower bound ? Circuits, why non-uniformity is needed, lower bounds for circuits, relation to parallel computing
- Should I toss a coin ? randomness, BPP, RP, BPP and circuit classes; hardness vs randomness
- Let's talk ! Interaction, IP, PSPACE, PCPs, communication complexity. Link to approximation hardness.
- Wave/particle ? rudimentary quantum complexity: BQP vs NP.
- Computation and Logic: Fagin's theorem
Things deliberately omitted because the audience is not specialist theory: oracles, natural proofs, sparseness, details of MA/AM/MIP=NEXP, Toda's theorem
For more, see Bill Gasarch's post and the comments.
Surprising things
- complementing affects time (we don't know that NP = co-NP) but not space (NSPACE = co-NSPACE!)
- non-determinism affects time (P ? NP) but not space (PSPACE = NPSPACE)
People/Research Groups
Books
- Complexity Theory: A Modern Approach by Arora and Barak
- Computational Complexity by Christos Papadimitriou
- Theory: Exploring the Limits of Efficient Algorithms by Ingo Wegener
- Computers and Intractability: A Guide to the Theory of NP-Completeness by Garey Johnson
- Elements of the Theory of Computation by Lewis Papadimitriou
- Automata and Computability by Kozen
- This book by Kozen is more advanced, but is nicely structured in bite-sized chapters.
- Introduction to the Theory of Computation by Michael Sipser
- An online book by Elaine Rich
Conferences
Blogs
- by William Gasarch
- In Theory, by Luca Trevisan.
- by Kurt Van Etten
Misc Links
- What is Theoretical Computer Science? by Sanjeev Arora
- A short history of computational complexity
- A graphical taxonomy of complexity classes
- The Theoretical Computer Science (TCS) Advocacy Wiki
- BEATCS
- Computational Complexity of Games and Puzzles
- A compendium of NP optimization problems maintained by Pierluigi Crescenzi and Viggo Kann
Non-trivial Trivia (.....pardon the oxymoron)
1. Did you know how many complexity classes are there ?
guess.....guess more.....here's the answer
2. Did ever you ever think that P and NP weren't "quite" properly named ?
Well, here's someone who thinks so !!
3. One may draw inspiration from the size of this group !!
Theoreticians aren't that scary creatures afterall :)
4. The myriad complexity classes offer a potential research problem to NLP researchers
5. .........more to follow
0*. And last but not the least here's a reason (courtesy Suresh) as to why we should keep this informal discussion group going
[*] - numbered zero because I think that it ought to be the first and most important reason but anyhow decided to put it at the end