"Steven D'Aprano" wrote in message news:[email protected]...
On Sun, 14 Jan 2018 10:30:31 +0200, Frank Millman wrote:
> I can detect a cycle in a path. It is possible for there to be more than
> one gateway in the path. I want to identify the gateway that actually
> triggered the cycle, but I have not figured out a way to do this.
You don't need a gateway to get a cycle. Suppose you have nodes
A -> B -> C -> D -> B
that's a cycle with no gateways.
[skip more good examples]
The usual way of fixing this sort of thing for systems intended for non-
expert use is to have a (user-configurable?) limit on the number of
steps, and have the process raise an error once it reaches the limit.
> After that, in the path returning to the previous node, there is another
> gateway that checks a counter. If the boolean check fails three times,
> terminate the process.
What boolean check? You mentioned a counter -- that's normally considered
to be an integer.
Sorry, I left out a couple of steps. In my imaginary process, every time the
boolean check in the first gateway fails, it increments a counter. The
second gateway checks the counter, and terminates the process if it exceeds
a limit.
Try googling for "Halting problem" to learn why you cannot, in general,
prove that all cycles will eventually terminate. You may be able to
identify *some* non-terminating graphs, but you cannot determine all of
them.
I will do so. Thanks for clearing up some confusion and giving me some
pointers.
Frank
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