Undecidable problems about turing machines pdf writer

A problem is decidable if we can construct a Turing machine which will halt in finite amount of time for every input and give answer as 'yes' or 'no'. A decidable problem has an algorithm to determine the answer for a given input. Note: Two popular undecidable problems are halting problem of CISC462, Fall 2018, Decidability and undecidability 1 DECIDABILITY AND UNDECIDABILITY Decidable problems from language theory For simple machine models, such as nite automata or pushdown automata, many decision problems are solvable. In the case of deterministic nite automata, problems like equivalence can be solved even in polynomial time. Given two total Turing machines, is it undecidable problem to detect whether they give the same output on all inputs? The problem. Do two halting Turing machines accept the same language I would say that in general it is undecidable: in fact, this problem can be reduced to the Halting Turing Machines And Undecidability notes for Computer Science Engineering (CSE) is made by best teachers who have written some of the best books of Computer Science Engineering (CSE). For an undecidable language, there is no Turing Machine which accepts the language and makes a decision for every input string w (TM can make decision for some input string though). A decision problem P is called "undecidable" if the language L of all yes instances to P is not decidable. Undecidable languages are not recursive languages, but sometimes, they may be recursively enumerable Part 2: Undecidability. In this second part of the post we'll discuss about undecidability. A problem is said undecidable if there's no algorithm to solve it, that is, no TM that is guaranteed to halt on all its inputs.. The Turing Machine Paradox. Question: Are Turing machines powerful enough so that for any language there exists a corresponding TM that defines it? 3 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. It's important to note that Halting problem depends on what programs we're considering. The halting problem on Turing machines is undecidable. Conversely, the halting problem on finite state automata is easily decidable; all finite state automata halt. Thus it's important to specify the model. The halting problem on usual computers is also No undecidable problem can ever be solved by a computer or computer program of any kind. In particular, there is no Turing machine to solve an undecidable problem. We have not said that undecidable means we don't know of a solution today but might find one tomorrow. It means we can never find an algorithm for the problem. Can a Turing machine be both decidable and undecidable relative to itself? Ask Question A Turing machine doesn't come with an oracle. The oracle comes from outside. Proving that the halting problem is not Turing-reducible to the acceptance problem for Turing machines. 1. If the machine keeps computing forever, we consider that the machine has rejected the string but it does so in an infinite number of steps. Thus, if the machine accepts a string, it must do so in a finite number of steps! A Language of a Turing Machi