How To Show Language Is Undecidable

how to show language is undecidable

Halting Problem Halting Problem is Undecidable
Undecidable Languages Equivalent language: AH = { TM M halts on input w} Need to show AH is undecidable We know ATM = { TM M accepts w} is undecidable Show ATM is reducible to AH (Theorem 5.1 in text) Suppose AH is decidable there’s a decider MH for AH Then, we can construct a decider DTM for ATM: On input , run MH on . If MH rejects, then REJ (this takes care …... The problem is known to be undecidable (but semidecidable). Your language L is indeed undecidable. This can be shown by reducing the halting problem to L: For the halting problem instance (N, y), create a new machine M for the L problem. On input x, M simulates (N, y) for length(x) steps.

how to show language is undecidable

6.8 The Post Correspondence Problem

Lecture 17: Proving Undecidability 13 Acceptance Language A TM= { < M, w> M is a TM description and M accepts input w} We proved ATM is undecidable last class. Since we know ATM is undecidable, we can show a new language B is undecidable if a machine that can decide B could be used to build a machine that can decide ATM....
This known undecidable language can be any language for which undecidability has been proved in the textbook, in lectures, in class handouts, or in homework problems (but …

how to show language is undecidable

Homework 8 Undecidable languages
The Totality Problem is Undecidable. The halting problem can be used to show that other problems are undecidable. Totality Problem: A function (or program) F is said to be total if F(x) is defined for all x (or similarly, if F(x) halts for all x). how to stop your period instantly Explicit undecidable language The previous theorem shows that undecidable languages exist but it doesn’t give any hint how such languages might look like. The following theorem shows an explicit language that is undecidable.. How to show your ip address in command prompt

How To Show Language Is Undecidable

Turing Decidable and Recognizable Languages

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How To Show Language Is Undecidable

More Undecidable Problems Rice’s Theorem Post’s Correspondence Problem Some Real Problems. 2 Properties of Languages Any set of languages is a property of languages. Example: The infiniteness property is the set of infinite languages. 3 Properties of Langauges – (2) As always, languages must be defined by some descriptive device. The most general device we know is the TM. Thus, we shall

  • Today: Undecidability, Recognition, Enumeration, all that good stuff Definition: A Turing Machine is a 7-tuple One can often show that a language L is undecidable by showing that if L is decidable, then so is ATM We reduce ATM to the language L ATM ≤ L We showed: ATM ≤ HALT TM and ATM ≤ ¬¬¬¬EMPTY TM Mapping Reductions f : Σ* →→→Σ* is a computable function if there is a
  • Show that the language of codes for TM’s M that, when started with a blank tape, eventually writes a 1 somewhere on the tape is undecidable. We will reduce from the problem of deciding whether a Turing machine accepts a given
  • Formulate this problem as a language, and show that it is undecidable. 11. Consider the problem of determining whether a Turing machine M on an input w ever attempts to move its head left when its head is on the left-most tape cell. Formulate this problem as a language and show that it is undecidable. 12. Consider the problem of determining whether a Turing machine M on an input w ever
  • Lecture 7: Other undecidable languages, Rice’s theorem, and Reductions Valentine Kabanets October 4, 2016 1 Semi-decidable vs. decidable We know that a language …

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