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CS311
Automata and Complexity Theory
Admistrative Stuff
• Instructor: Shahab Baqai ([email protected])Room # 428, Ext 4428
• Lectures: Mon & Wed 1530 – 1710 hrs. A-9
• Tutorials: As & When needed
• Office Hrs: Mon & Wed 1720 – 1820 hrs
• TAs: 3~4 (TBA) – Check course web foroffice hours etc
• Prerequisite: CS211 - Discrete Mathematics
•Website: http://suraj.lums.edu.pk/~cs311a04
Admistrative Stuff (cont.)
Questions: We prefer that you post your question to the class discussion form. The TA will try to respond to all questions on the form within 24 hours (48 hours Max). This way everyone gets the benefit of reading the replies, and it helps to reduce the number of repeat questions.
For questions that are not suitable to be posted to the newsgroup (e.g. questions about your grade), you can email your TA directly although there is no guarantee of when you will receive a reply.
Course Organization
Text Book: SJ. E. Hopcroft, R. Motwani, and J. D. Ullman Introduction to Automata Theory,Languages, and Computation, Second Edition,Addison-Wesley, New York, 2001.
Sections: There are two parallel sections. The material covered in each will be the same. The 6~8 assignments, midterm and Final will becommon. Each section may have different quizzes.
Weights: Homework 06~08%Quizzes 17~19%Midterm 35%Final Exam 40%
What we will do
•Automata = abstract computing devices
•Turing studied Turing Machines (= computers)before there were any real computers
•We will also look at simpler devices thanTuring machines (Finite State Automata, Pushdown Automata, . . . ), and specification means, such as grammars and regular expressions.
•NP-hardness = what cannot be efficiently computed
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Computation
CPU memory
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CPU
input memory
output memory
Program memory
temporary memory
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CPU
input memory
output memoryProgram memory
temporary memory
3)( xxf
compute xx
compute xx 2
Example:
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CPU
input memory
output memoryProgram memory
temporary memory
3)( xxf
compute xx
compute xx 2
2x
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CPU
input memory
output memoryProgram memory
temporary memory3)( xxf
compute xx
compute xx 2
2x
42*2 z82*)( zxf
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CPU
input memory
output memoryProgram memory
temporary memory3)( xxf
compute xx
compute xx 2
2x
42*2 z82*)( zxf
8)( xf
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Automaton
CPU
input memory
output memory
Program memory
temporary memory
Automaton
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Different Kinds of Automata
Automata are distinguished by the temporary memory
• Finite Automata: no temporary memory
• Pushdown Automata: stack
• Turing Machines: random access memory
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input memory
output memory
temporary memory
Finite
Automaton
Finite Automaton
Example: Vending Machines
(small computing power)
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input memory
output memory
Stack
Pushdown
Automaton
Pushdown Automaton
Example: Compilers for Programming Languages
(medium computing power)
Push, Pop
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input memory
output memory
Random Access Memory
Turing
Machine
Turing Machine
Examples: Any Algorithm
(highest computing power)
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Finite
Automata
Pushdown
Automata
Turing
Machine
Power of Automata
Less power More power
Solve more
computational problems