'Undecidable problems' diaporamas de présentation

Reductions

Reductions. Problem is reduced to problem. If we can solve problem then we can solve problem. Definition:. Language is reduced to language There is a computable function ( reduction ) such that:. Recall:. Computable function : .

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Chapter 8 Introduction to Turing Machines

Chapter 8 Introduction to Turing Machines. Rothenberg, Germany. Outline. Problems that Computers Cannot Solve The Turing Machine (TM) Programming Techniques for TM’s Extensions to the Basic TM Restricted TM’s TM’s and Computers. 8.0 Introduction. Concepts to be taught ---

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More Undecidable Problems

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The Post Correspondence Problem

The Post Correspondence Problem. Some undecidable problems for context-free languages:. Is ?. are context-free grammars. Is context-free grammar ambiguous?. We need a tool to prove that the previous problems for context-free languages

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The Science of Insecurity

The Science of Insecurity. Len Sassaman Meredith L. Patterson Sergey Bratus. Tribute to Len Sassaman. Anonymity/ privacy researcher, cypherpunk Moved to language-theoretic security in 2009 Because the future of an open Internet depends on smoothing out the attack surface. 1980 - 2011.

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David Evans http://www.cs.virginia.edu/evans

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Undecidable Problems From Language Theory

Undecidable Problems From Language Theory. Lecture 33 Section 5.1 Wed, Nov 7, 2007. Reducibility. A problem A is reducible to a problem B if a solution to B gives us a solution to A . More specifically, an instance of problem A can be restated as an instance of problem B .

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Undecidable Problems From Language Theory

Undecidable Problems From Language Theory. Lecture 33 Section 5.1 Wed, Nov 7, 2007. Reducibility. A problem A is reducible to a problem B if a solution to B gives us a solution to A . More specifically, an instance of problem A can be restated as an instance of problem B .

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Decidability

Decidability. A decision problem is a problem for which the answer is either "yes" or "no". A decidable problem is a decision problem that has a solution algorithm. A semidecidable problem is a decision problem for which there is a decision procedure

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CS 3240: Languages and Computation

CS 3240: Languages and Computation. Turing Machines. Properties of CFGs. Undecidable problems for CFL. Turing Machines. Reducibility among problems. Turing Machine. Moves of a TM. Acceptance by halting. Variations of TMs. Project 1. Building an Expanded Suffix Tree.

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