Path: ...!3.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory,sci.logic Subject: Re: Termination analyzer defined ---RICHARD IS WRONG !!! Date: Tue, 14 May 2024 09:18:40 -0500 Organization: A noiseless patient Spider Lines: 48 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Tue, 14 May 2024 16:18:40 +0200 (CEST) Injection-Info: dont-email.me; posting-host="e9b15de5cbd4b611ca4438a3f5fabf94"; logging-data="234727"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18gHnr6RXekF3nMb9BWMZZQ" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:53nSfUF8H9FyaTgSfS4RU5XxT4I= In-Reply-To: Content-Language: en-US Bytes: 3075 On 5/14/2024 4:34 AM, Mikko wrote: > On 2024-05-13 18:07:37 +0000, Jeff Barnett said: > >> On 5/13/2024 3:06 AM, Mikko wrote: >> >>> Anyway, if an analyzer can never tell whether a program terminates >>> with every possible input then it is not a termination analyzer. >> >> I don't think the above is true in the way you meant it. Recall that >> the collection of all Turing machines with blank input tapes is the >> same set of computations as the collection with arbitrary input tapes. >> It's always possible to take any specific machine, T, and initial >> tape, I, and produce machine T' with blank initial input tape that is >> equivalent: T' initially writes I on its tape (say one character >> output per state in sequence) then continues with the set of states >> that comprises T. >> >> So it is obvious that a termination analyzer (AKA a halt decider) >> restricted to blank tape problems will do quite nicely and it is also >> quite obvious that no such entity exists. > > You only discuss halting decisions with specific inputs. THerefore you say > nothing about termination analyzers and don't show any mistake in my > comment. > 00 int H(ptr x, ptr x) // ptr is pointer to int function 01 int D(ptr x) 02 { 03 int Halt_Status = H(x, x); 04 if (Halt_Status) 05 HERE: goto HERE; 06 return Halt_Status; 07 } 08 09 int main() 10 { 11 H(D,D); 12 } In any case you diverged away form the whole point of this thread. Richard is wrong when he says that there exists an H/D pair such that D simulated by H ever reaches past its own line 03. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer