TikhonJelvis / imp

Some scripts for analyzing IMP programs with the Z3 automatic theorem prover, originally written for my Compose 2016 talk.
http://jelv.is/talks/compose-2016
BSD 3-Clause "New" or "Revised" License
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Proofs of (non-looping) non-termination and associated pattern synthesis #4

Open void4 opened 5 months ago

void4 commented 5 months ago

I've been wondering if it is possible to add a non-termination proof ability to IMP. I don't understand any of the existing methods used in provers like AProVE yet, but they seem to try to generate patterns rules/"shapes" which describe recurring behavior compactly, because an "infinite loop unroll" is not possible.

I don't know how to describe the following thought formally, but I'll try:

Most non-termination provers only seem to handle looping non-termination, which can be difficult enough. But the "shape" of non-looping non-terminating behavior can be arbitrarily complex. Existing provers only seem to be capable of generating/recognizing a limited set of "shapes" of behaviors - could some form of synthesis be used to define/explore more (or even all) of them?

In other words, it feels to me like if the types of pattern rules a prover supports is limited, it will never be able to find all forms of non-termination. Is it possible for some kind of "turing-complete-pattern-synthesis" to have a chance to encounter all possible non-halting patterns at least "in the limit"?