source: vis_dev/vis-2.3/share/help/model_checkCmd.txt @ 50

  model_check - perform fair CTL model checking on a flattened network
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   model_check [-b] [-c] [-d <dbg_level>] [-f <dbg_file>] [-g <hints_file>]
   [-h]  [-i]  [-m] [-r] [-t <time_out_period>][-v <verbosity_level>] [-D
   <dc_level>] [-F] [-S <schedule>] [-V] [-B] [-I] [-C] [-w <node_file>] [-W]
   [-G] <ctl_file>

   Performs fair CTL model checking on a flattened network. Before calling this
   command, the user should have initialized the design by calling the command
   [1]init_verify. Regardless of the options, no 'false positives' or 'false
   negatives' will occur: the result is correct for the given circuit.

   Properties to be verified should be provided as CTL formulas in the file
   ctl_file. Note that the support of any wire referred to in a formula should
   consist only of latches. For the precise syntax of CTL formulas, see the
   [2]VIS CTL and LTL syntax manual.

   Properties  of  the form AG f, where f is a formula not involving path
   quantifiers are referred to as invariants; for such properties it may be
   substantially faster to use the [3]check_invariant command.

   A fairness constraint can be specified by invoking the [4]read_fairness
   command; if none is specified, all paths are taken to be fair. If some
   initial states do not lie on a fair path, the model checker prints a message
   to this effect.

   A  formula passes iff it is true for all initial states of the system.
   Therefore, in the presence of multiple initial states, if a formula fails,
   the negation of the formula may also fail.

   If  a  formula does not pass, a (potentially partial) proof of failure
   (referred to as a debug trace) is demonstrated. Fair paths are represented
   by a finite sequence of states (the stem) leading to a fair cycle, i.e. a
   cycle on which there is a state from each fairness condition. The level of
   detail of the proof can be specified (see option -d).

   Both  backward (future tense CTL formulas) and forward (past tense CTL
   formulas) model checking can be performed. Forward model checking is based
   on Iwashita's ICCAD96 paper. Future tense CTL formulas are automatically
   converted to past tense ones as much as possible in forward model checking.

   Command options:

   -b
          Use backward analysis when performing debugging; the default is to
          use forward analysis. This should be tried when the debugger spends a
          large amount of time when creating a path to a fair cycle. This
          option is not compatible with forward model checking option (-F).

   -c
          Use the formula tree so that there is no sharing of sub-formulae
          among the formulae in the input file. This option is useful in the
          following scenario - formulae A, B and C are being checked in order
          and  there  is sub-formula sharing between A and C. If the BDDs
          corresponding to the shared sub-formula is huge then computation for
          B might not be able to finish without using this option.

   -d <dbg_level>
          Specify the amount of debugging performed when the system fails a
          formula being checked. Note that it may not always be possible to
          give a simple counter-example to show that a formula is false, since
          this may require enumerating all paths from a state. In such a case
          the model checker will print a message to this effect. This option is
          incompatible with -F.

          dbg_level must be one of the following:

          0: No debugging performed. dbg_level=0 is the default.

          1: Debugging with minimal output: generate counter-examples for
          universal formulas (formulas of the form AX|AF|AU|AG) and witnesses
          for existential formulas (formulas of the form EX|EF|EU|EG). States
          on a path are not further analyzed.

          2:  Same as dbg_level=1, but more verbose. (The subformulas are
          printed, too.)

          3: Maximal automatic debugging: as for level 1, except that states
          occurring on paths will be recursively analyzed.

          4: Manual debugging: at each state, the user is queried if more
          feedback is desired.

   -f <dbg_file>
          Write the debugger output to dbg_file. This option is incompatible
          with  -F. Notes: when you use -d4 (interactive mode), -f is not
          recommended, since you can't see the output of vis on stdout.

   -g <hints_file>
          Use guided search. The file hints_file contains a series of hints. A
          hint is a formula that does not contain any temporal operators, so
          hints_file has the same syntax as a file of invariants used for
          check_invariant. The hints are used in the order given to change the
          transition relation. In the case of least fixpoints (EF, EU), the
          transition relation is conjoined with the hint, whereas for greatest
          fixpoints the transition relation is disjoined with the negation of
          the hint. If the hints are cleverly chosen, this may speed up the
          computation  considerably,  because  a  search with the changed
          transition relation may be much simpler than one with the original
          transition relation, and results obtained can be reused, so that we
          may never have to do a complicated search with the original relation.
          Note: hints in terms of primary inputs are not useful for greatest
          fixpoints. See also: Ravi and Somenzi, Hints to accelerate symbolic
          traversal. CHARME'99; Bloem, Ravi, and Somenzi, Efficient Decision
          Procedures  for Model Checking of Linear Time Logic Properties,
          CAV'99; Bloem, Ravi, and Somenzi, Symbolic Guided Search for CTL
          Model Checking, DAC'00.

          For formulae that contain both least and greatest fixpoints, the
          behavior depends on the flag guided_search_hint_type. If it is set to
          local (default) then every subformula is evaluated to completion,
          using all hints in order, before the next subformula is started. For
          pure   ACTL   or   pure   ECTL   formulae,   we  can  also  set
          guided_search_hint_type to global, in which case the entire formula
          is evaluated for one hint before moving on to the next hint, using
          underapproximations. The description of the options for guided search
          can be found in the help page for print_guided_search_options.

          model_check will call reachability without any guided search, even if
          -g is used. If you want to perform reachability with guided search,
          call rch directly.

          Incompatible with -F.

   -h
          Print the command usage.

   -i
          Print  input  values  causing transitions between states during
          debugging. Both primary and pseudo inputs are printed. This option is
          incompatible with -F.

   -m
          Pipe debugger output through the UNIX utility more. This option is
          incompatible with -F.

   -r
          Reduce the FSM derived from the flattened network with respect to
          each formula being checked. By default, the FSM is reduced with
          respect to the conjunction of the formulae in the input file. If this
          option is used and don't cares are being used for simplification,
          then  subformula sharing is disabled (result might be incorrect
          otherwise).

          The truth of a formula may be independent of parts of the network
          (such as when wires have been abstracted; see [5]flatten_hierarchy).
          These parts are effectively removed when this option is invoked; this
          may result in more efficient model checking.

   -t <timeOutPeriod>
          Specify the time out period (in seconds) after which the command
          aborts. By default this option is set to infinity.

   -v <verbosity_level>
          Specify verbosity level. This sets the amount of feedback on CPU
          usage and code status.
          verbosity_level must be one of the following:

          0: No feedback provided. This is the default.

          1: Feedback on code location.

          2: Feedback on code location and CPU usage.

   -B
          Check for vacuously passing formulae using the algorithm of Beer et
          al. (CAV97). The algorithm applies to a subset of ACTL (w-ACTL) and
          replaces the smallest important subformula of a passing property with
          either  FALSE or TRUE depending on its negation parity. It then
          applies model checking to the resulting witness formula. If the
          witness formula also passes, then the original formula is deemed to
          pass vacuously. If the witness formula fails, a counterexample to it
          provides an interesting witness to the original passing formula. See
          the CAV97 paper for the definitions of w-ACTL, important subformula,
          and interesting witness. In short, one of the operands of a binary
          operator in a w-ACTL formula must be a propositional formula. See
          also the -V option.

   -C
          Compute coverage of all observable signals in a set of CTL formulae
          using  the algorithm of Hoskote, Kam, Ho, Zhao (DAC'99). If the
          verbosity level (-v option) is equal to 0, only the coverage stats
          are printed. If verbosity level is greater than zero, then detailed
          information of the computation at each step of the algorithm is also
          provided. Debug information is provided in the form of states not
          covered for each observable signal if the dbg_level (-d option) is
          greater  than 0. The number of states printed is set by the vis
          environment variable 'nr_uncoveredstates'. By default the number of
          states printed is 1. The value of nr_uncoveredstates can be set using
          the set command. See also the -I option.

   -D <dc_level>
          Specify extent to which don't cares are used to simplify MDDs in
          model checking. Don't cares are minterms on which the values taken by
          functions do not affect the computation; potentially, these minterms
          can be used to simplify MDDs and reduce the time taken to perform
          model checking. The -g flag for guided search does not affect the way
          in which the don't-care conditions are computed.
          dc_level must be one of the following:

          0 : No don't cares are used.

          1 : Use unreachable states as don't cares. This is the default.

          2 : Use unreachable states as don't cares and in the EU computation,
          use 'frontiers' for image computation.

          3  : First compute an overapproximation of the reachable states
          (ARDC), and use that as the cares set. Use `frontiers' for image
          computation. For help on controlling options for ARDC, look up help
          on the command: [6]print_ardc_options. Refer to Moon, Jang, Somenzi,
          Pixley, Yuan, "Approximate Reachability Don't Cares for {CTL} Model
          Checking",  ICCAD98,  and to two papers by Cho et al, IEEE TCAD
          December 1996: one is for State Space Decomposition and the other is
          for Approximate FSM Traversal.

   -F
          Use forward model checking based on Iwashita's method in ICCAD96.
          Future tense CTL formulas are automatically converted to past tense
          ones as much as possible. Converted forward formulas are printed when
          verbosity is greater than 0. Debug options (-b, -d, -f, -i, and -m)
          are  ignored  with this option. We have seen that forward model
          checking was much faster than backward in many cases, also forward
          was much slower than backward in many cases.

   -I
          Compute coverage of all observable signals in a set of CTL formulae
          using  an  improved  algorithm of Jayakumar, Purandare, Somenzi
          (DAC'03). If the verbosity level (-v option) is equal to 0, only the
          coverage stats are printed. If verbosity level is greater than zero,
          then detailed information of the computation at each step of the
          algorithm is also provided. Debug information is provided in the form
          of states not covered for each observable signal if the dbg_level (-d
          option) is greater than 0. The number of states printed is set by the
          vis environment variable 'nr_uncoveredstates'. By default the number
          of states printed is 1. The value of nr_uncoveredstates can be set
          using the set command. Compared to the -C option, this one produces
          more accurate results and deals with a larger subset of CTL.

   -S <schedule>
          Specify schedule for GSH algorithm, which generalizes the Emerson-Lei
          algorithm and is used to compute greatest fixpoints. The choice of
          schedule  affects the sequence in which EX and EU operators are
          applied. It makes a difference only when fairness constraints are
          specified.
          <schedule> must be one of the following:

          EL : EU and EX operators strictly alternate. This is the default.

          EL1 : EX is applied once for every application of all EUs.

          EL2 : EX is applied repeatedly after each application of all EUs.

          budget : a hybrid of EL and EL2.

          random : enabled operators are applied in (pseudo-)random order.

          off : GSH is disabled, and the old algorithm is used instead. The old
          algorithm uses the EL schedule, but the termination checks are less
          sophisticated than in GSH.

   -V
          Check for vacuously passing formulae with the algorithm of Purandare
          and Somenzi (CAV2002). The algorithm applies to all of CTL, and to
          both  passing and failing properties. It says whether a passing
          formula may be strengthened and still pass, and whether a failing
          formula may be weakened and still fail. It considers all leaves of a
          formula that are under one negation parity (e.g., not descendants of
          a XOR or EQ node) for replacement by either TRUE or FALSE. See also
          the -B option.

   -w <node_file> This option invoked the algorithm to generate an error trace
          divided into fated and free segements. Fate represents the
          inevitability and free is asserted when there is no inevitability.
          This can be formulated as a two-player concurrent reachability game.
          The two players are the environment and the system. The node_file is
          given to specify the variables the are controlled by the system.

   -W
   This option represents the case that all input variables are controlled by
          system.

   -G
   We proposed two algorithm to generate segemented counter example. They are
          general and restrcited algorithm. Bu default we use restricted
          algorithm. We can invoke general algorithm with -G option. For more
          information, please check the STTT'04 paper of Jin et al., "Fate and
          Free Will in Error Traces"

   <ctl_file>
          File containing CTL formulas to be model checked.

   Related "set" options:

   ctl_change_bracket <yes/no>
          Vl2mv automatically converts "[]" to "<>" in node names, therefore
          CTL parser does the same thing. However, in some cases a user does
          not want to change node names in CTL parsing. Then, use this set
          option by giving "no". Default is "yes".

   guided_search_hint_type
          Switches between local and global hints (see the -g option, or the
          help page for set).

   See also commands : approximate_model_check, incremental_ctl_verification
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   Last updated on 20100410 00h02

References

   1. file://localhost/projects/development/hsv/vis/common/doc/html/init_verifyCmd.html
   2. file://localhost/projects/development/hsv/vis/common/doc/ctl/ctl/ctl.html
   3. file://localhost/projects/development/hsv/vis/common/doc/html/check_invariantCmd.html
   4. file://localhost/projects/development/hsv/vis/common/doc/html/read_fairnessCmd.html
   5. file://localhost/projects/development/hsv/vis/common/doc/html/flatten_hierarchyCmd.html
   6. file://localhost/projects/development/hsv/vis/common/doc/html/print_ardc_optionsCmd.html