November 1

November 1 - CSCI 2670 Introduction to Theory of Computing...

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CSCI 2670 Introduction to Theory of Computing November 1, 2005
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November 1, 2005 Agenda • Last week •Today – Review one undecidability proof – Rice’s Theorem – Reductions (Section 5.3)
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November 1, 2005 Announcements Announcements • Homework due next Tuesday (11/8) – 5.7, 5.12 (do not use Rice’s Theorem), 5.20, 5.22, 5.30 b •O ld
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November 1, 2005 An undecidable language Let REGULAR TM = {<M> | M is a TM and L(M) is a regular language} Theorem : REGULAR TM is undecidable Proof : Assume R decides REGULAR TM and use R to decide A TM (reduce the A TM problem to the REGULAR TM problem). As before, make a new TM, M 2 , that accepts a regular language iff M accepts w.
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Proof (cont.) Consider the following TM S = “On input <M,w> 1. Construct the following TM M 2 M 2 = “On input x 1. If x = 0 n 1 n for some n, accept 2. Otherwise, run M on w. If M accepts w, accept 2. Run R on M
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This note was uploaded on 02/07/2011 for the course CS 501 taught by Professor Sm during the Spring '11 term at Indiana.

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November 1 - CSCI 2670 Introduction to Theory of Computing...

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