Removing State Variables

From: Fabio Somenzi (Fabio@colorado.edu)
Date: Sat May 26 2001 - 15:44:16 MDT

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    >>>>> "vg" == vanessa goyal <vanessa_goyal@rediffmail.com> writes:

     vg> In the example of ARBITER three controllers have register for
     vg> passtoken variable. There are no states in which more than one
     vg> passtoken will be set. so we can remove such states and reduce
     vg> state space. Is it possible in VIS?

    No, it is not possible. There are algorithms to detect that some
    state variables are expressible as combinations of others. There have
    been a couple of experimental implementations in VIS, but none has
    been included in the released version thus far.

    The earliest work on the subject is probably

    @INPROCEEDINGS { Berthe90 ,
            AUTHOR = "C. Berthet and O. Coudert and J. C. Madre" ,
            BOOKTITLE = iccd ,
            MONTH = oct ,
            TITLE = "New Ideas on Symbolic Manipulation of Finite State Machines" ,
            YEAR = "1990"
            }

    One of the most recent is:

    @INCOLLECTION { Yang99b ,
            ADDRESS = "Berlin" ,
            AUTHOR = "B. Yang and R. Simmons and R. E. Bryant and D. R. O'Hallaron" ,
            BOOKTITLE = "Eleventh Conference on Computer Aided Verification (CAV'99)" ,
            EDITOR = "N. Halbwachs and D. Peled" ,
            NOTE = "LNCS 1633" ,
            PAGES = "328-340" ,
            PUBLISHER = "Springer-Verlag" ,
            TITLE = "Optimizing Symbolic Model Checking for Constraint-Rich Models" ,
            YEAR = "1999"
            }

    Fabio



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