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Re: [tlaplus] TLAPS-proved invariant violated in TLC?
Hehe, I never thought my cargo cult approach could be of any good use. :D
On 17.10.2015 10:32, Stephan Merz wrote:
> Dear Jaak,
> what should not have worked in your proof are the level-2 steps that prove a non-temporal obligation "BY PTL". (Note that the proof does not even use the CASE assumption or the definitions of formulas NextComponent.)
> I just tried this and PTL indeed accepts these steps. It wrongly considers the assumption "Invariant" to occur in a boxed context (i.e., it assumes it to always hold) and therefore has no problem proving that Invariant' must be true. In fact, it even accepts the bogus proof
> <1>2. Invariant /\ [Next]_vars => Invariant'
> <2> SUFFICES ASSUME Invariant,
> PROVE Invariant'
> <2> QED BY PTL
> This is a serious bug in the handling of temporal contexts that we need to fix in the code of TLAPS. Until we do so, please be sure not to use PTL for a non-temporal proof in the context of a SUFFICES ASSUME ... PROOF step.
> Thanks for reporting this!
>> On 16 Oct 2015, at 13:07, Jaak Ristioja <jaak.r...@xxxxxxxx> wrote:
>> During designing a (proprietary) protocol I've reached a point where
>> I've proved (all highlighted green in TLA+ Toolbox) an invariant like
>> THEOREM InvariantHolds == Spec => Invariant \* All green
>> <1>1. Init => Invariant PROOF OMITTED \* For this e-mail
>> <1>2. Invariant /\ [Next]_vars => Invariant'
>> <2> SUFFICES ASSUME Invariant
>> PROVE Invariant'
>> <2>1. CASE NextComponent BY PTL
>> <2>2. CASE NextComponent2 BY PTL
>> \* ...
>> <2>3. QED BY <2>1, <2>2 (* ... *) DEF Next
>> <1>3. QED BY <1>1, <1>2, PTL DEF Spec
>> But when I run the protocol TLC it reports that the invariant Invariant
>> is violated. After debugging this for a while I found a bug in my
>> Invariant which explains why it failed in TLC. Is it incorrect of me to
>> assume TLAPS has successfully proved the theorem when the TLA+ Toolbox
>> hightlights the theorem all green a pressing CTRL+G on it twice? Am I
>> doing something wrong or is this a bug?
>> Best regards,
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