Re: query automaton

[Vladimir Makarov <vmakarov at redhat dot com>]

Alex Turjan wrote:
> Dear Vladimir,     
>   
> > Not really.  There is no requirement for "the units
> > part of the alternatives of a reservation must belong to the
> > same automaton".  Querying should also work in this
> > case because function cpu_unit_reservation_p checks all
> > automata for an unit reservation. 
> >     
> Indeed it checks all automata but Im afraid that according to my pipeline description this check is not enough to guarantee a correct scheduling decision, e.g.,
> suppose the following insn reservation: 
>
> (define_reservation "move"  "(  (unit1_aut1, unit1_aut2) |              (*)
>                                 (unit2_aut1, unit2_aut2)  ) 
>
> ,where unitN_autM refers to unit N from automata M. In this case there are 2 automata. 
> Now supose a scheduling state S made of the individual states of the two automatons S=<S_aut1,S_aut2>. According to what I see happening in insn-automata.c (and target.dfa), from S_aut1 there is a transition for unit1_aut1 and from S_aut2 there is a transition for unit2_aut2. 
>
> It seems that the automata do not communicate with each other. As a consequence, 
> A scheduling decision which results in the resource reservation  
> (unit1_aut1, unit2_aut2)  would not be rejected, while it should. 
>  
> In my opinion, the current implementation sees the reservation defined in (*)
> As equivalent to the following one
> (define_reservation "move"  "(  (unit1_aut1| unit2_aut1) ,
>                                 (unit1_aut2| unit2_aut2)  ) 
> Which does not seem  true to me. 
>
> Is there a way for automatons to communicate so that the alternative 
> (unit1_aut1, unit2_aut2) would be rejected?
>
>   
Last two days, I've been working on this issue.  I found that you are 
right, genautomata permits to generate incorrect automata although I did 
not find that it is a case for major current description which I checked.

I found the issue is complicated.  Genuatomata has already a check for 
correct automata generations in check_regexp_units_distribution but that 
is not enough.  I am working on formulation of general rules for correct 
automata generation and implementation of their check.  I think it will 
take a week or two to do this and check how does it work for all current 
automata description.

Alex, thanks for pointing out this issue to me.