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TLA+ Threads example
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| SPECIFICATION Spec | |
| PROPERTY Liveness | |
| CHECK_DEADLOCK FALSE |
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| ---- MODULE threads ---- | |
| EXTENDS Integers, Sequences | |
| VARIABLES pc, counter, tmp | |
| vars == <<pc, counter, tmp>> | |
| NumThreads == 2 | |
| Threads == 1..NumThreads | |
| States == {"start", "inc", "done"} | |
| Trans(thread, from, to) == | |
| /\ pc[thread] = from | |
| /\ pc' = [pc EXCEPT ![thread] = to] | |
| Init == | |
| /\ pc = [t \in Threads |-> "start"] | |
| /\ counter = 0 | |
| /\ tmp = [t \in Threads |-> 0] | |
| GetCounter(t) == | |
| /\ tmp' = [tmp EXCEPT ![t] = counter] | |
| /\ UNCHANGED counter | |
| IncCounter(t) == | |
| /\ counter' = tmp[t] + 1 | |
| /\ UNCHANGED tmp | |
| Next == | |
| \/ \E t \in Threads: | |
| \* Step to get the counter value | |
| \/ /\ Trans(t, "start", "inc") | |
| /\ GetCounter(t) | |
| \* Step to increment the counter | |
| \/ /\ Trans(t, "inc", "done") | |
| /\ IncCounter(t) | |
| Spec == Init /\ [][Next]_vars | |
| Liveness == <>[](global = NumThreads) | |
| ==== |
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