Lecture15_Part2

Lecture15_Part2 - Introduction 1. We know that A is...

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Unformatted text preview: Introduction 1. We know that A is undecidable. 2. We want to prove B is undecidable. 3. We assume that B is decidable and use this assumption to prove that A is decidable. 4. We conclude that B is undecidable. Note: The reduction is from A to B. 6 Schematic of a Reduction Using a decider for L to construct a decider for ATM , is called reducing L to ATM . Note: Once we prove that a certain language L is undecidable, we can prove that some other language, say L' , is undecidable, by reducing L' to L. 5 Demonstration Demonstration 2. We want to prove B is undecidable. We pick HALTTM to play the role of B that is: We want to prove that HALTTM is undecidable. 3. We assume that B is decidable and use this assumption to prove that A is decidable. 1. We know that A is undecidable. The only undecidable language we know, so far, is ATM whose undecidability was proven directly. So we pick ATM to play the role of A. 2. We want to prove B is undecidable. 7 8 ...
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This note was uploaded on 04/30/2009 for the course CSE 105 taught by Professor Paturi during the Winter '99 term at UCSD.

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