13 Apr
2023
13 Apr
'23
5:47 p.m.
Hi Yoav,
Sorry for this delayed answer.
Yoav Ben Shimon <yoavbenshimon(a)gmail.com> writes:
I ran into a couple of issues when using SPOT in a
project. I'll be
glad for any assistance.
1) I am calling sat_minimize from a python script using the spot
python library. Is there any way to set a timeout on this function
call? Or do I have to use the CLI if I want a timeout?
I'm not aware of easy ways to deal with timeouts at the function level.
Those are usually set at the process level by using alarm() to trigger a
signal, and then usually killing the process when receiving this signal.
It seems easier to just runs this minimization as a separate process,
and use Python's subprocess module with a timeout.
2) I am manipulating an automaton generated from an
LTL formula, and
then printing it in HOA format. Is there a way to guarantee that the
initial state is the state numbered 0?
You should generally not assume that the initial state is 0.
You could swap the initial state with state 0 in a rather crude way
by iterating on the edge vector and fixing all source and destinations,
but that will cause issue if some named-properties are attached to the
automaton as those could be vectors indexed by state numbers (e.g., a
vector of strings naming each state). See the attachment for an
example that also removes all named properties as a security.
Another idea: the current version of the formater for the LBTT format
(compatible only with generalized Büchi acceptance) does relabels all
states in such a way that the initial state is 0. So while
ltl2tgba XXXGa
will print an HOA that does not start at state 0, using
ltl2tgba XXXGa --lbtt | autfilt
will print an HOA that start at 0. There is however nothing in the LBTT
format that forces us to start at 0, so this is unfortunately just
a side effect of how things are implemented.
If not, is there any other way to control the naming
of states?
You are probably talking about the numbering of states, but just for
completeness I'll add that the HOA format also allows you to name
states: those are strings attached to each state. In python you can
do
aut.set_state_names(["name for state 0",
"name for state 1", ...,
"name for state n-1"])
and those will be preserved in the HOA.
