source: vis_dev/vis-2.3/share/help/approximate_model_checkCmd.txt @ 60

  approximate_model_check - perform ACTL model checking on an abstracted and
  flattened network
     _________________________________________________________________

   approximate_model_check [-h] [-v <verbosity_level>] <ctl_file>

   Performs  ACTL  model checking on an abstracted and flattened network.
   Predefined  abstractions are performed prior to model checking. Before
   calling this command, the user should have initialized the design by calling
   the command [1]init_verify.

   The command includes two dual algorithms. The user should set appropriate
   environment  parameters  associated with the command to execute proper
   algorithm. By default, the command makes its effort to prove whether given
   ACTL formula is positive. To check whether the ACTL formula is negative,
   user should set the environment parameter amc_prove_false prior to executing
   the command. See [2]below for the environment parameters associated with
   this command.

   Properties to be verified should be provided as ACTL formulas in the file
   <ctl_file>. The command only accepts ACTL formulas. Mixed, ECTL expressions
   are not supported. ACTL formulas are those in which all quantifiers are
   universal and negation is only allowed at the level of atomic propositions.
   For the precise syntax of CTL formulas, see the [3]VIS CTL and LTL syntax
   manual.

   The command is designed to tackle the state explosion problem we encounter
   when dealing with large and complex circuits. Based on the initial size of
   the  group, the command constructs over- or under-approximation of the
   transition relation of the system. A group (subsystem) is a portion of the
   original circuit containing a subset of the latches and their next state
   functions.   The  initial  size  of  a  group  can  be  set  with  the
   [4]amc_sizeof_group environment variable. These initial approximations may
   not contain every detail of the exact system. However they may contain
   enough information to determine whether the formula is positive or negative.
   Starting from an initial coarse approximation, the command makes its effort
   to  prove whether given ACTL formula is positive or negative. When the
   procedure  fails  to  prove  correctness  of  the formula with initial
   approximations, it automatically refines the approximations. It repeats the
   process until the algorithm produces a reliable result or the available
   resources are exhausted.

   Due to the overhead procedures, for some circuits, the exact [5]model_check
   method may evaluate formulas faster with less resources. If any formula
   evaluates to false, a debug trace is reported.

   The command does not use fairness constraints even if they have been read
   with the [6]read_fairness command.

   Command options: 

   -h
          Print the command usage.

   -v <verbosity_level>
          Specify  verbosity  level.  verbosity_level  must be one of the
          following:

          0 : No feedback provided. This is the default.
          1 : Some feedback.
          2 : Lots of feedback.

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

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

   Environment Parameters:

   Environment parameters should be set using the set command from the VIS
   shell
   (e.g. vis> set amc_prove_false).

   amc_prove_false 
          When the parameter is set, the command makes its effort to prove
          whether given ACTL formula is negative. The command constructs a set
          of under-approximations of the transition relations of the system.
          When the formula evaluates to false, a debug trace is reported by
          default.

   amc_grouping_method <grouping method> 
          Specifies grouping method. Grouping method is a method for grouping
          number of latches into single subsystem. Two methods are supported.

          Grouping based on hierarchy(default) : The method groups latches
          based on the hierarchy of the system. Normally, complex circuits are
          designed  in  multiple processes. Furthermore, processes form a
          hierarchy. The method uses this information provided by the original
          design. When a design described in high level description language is
          transformed into low level BLIF format, the processes are transformed
          into subcircuits. The method groups those latches that are within
          same subcircuit.

          Grouping based on latch dependencies(latch_dependency): The method
          groups  those latches that are closely related. Closely related
          latches are those who has many (transitive) connections between them.

          When the parameter is not specified, the command by default uses
          hierarchical grouping method.

   amc_sizeof_group <integer value> 
          Determines the number of latches in each group(subsystem). The
          default value is 8. The initial size of the subsystem determines the
          initial degree of approximations of the transition relations. There's
          no proven rule of setting the value. Some experimental results show
          that setting the value to about 5-20% of overall number of latches is
          reasonable(e.g. if the system contains 100 latches set the value to
          5-20). However, the suggested range may not work well with some
          examples.

   amc_DC_level <integer value> 
          Specifies don't care levels. Default level is 0. Absence of the
          parameter sets the amc_DC_level to 0.
          amc_DC_level must be one of the following:

        0: No don't cares are used. This is the default.

        1: Use unreachable states as don't cares.

        2: Aggressively use DC's to simplify MDD's in model checking.

          Using don't cares may take more time for some examples since the
          approximate model checker computes the reachable states for each
          subsystem. For some large circuits it is undesirable to set don't
          care level.

   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".

   See also commands : model_check, incremental_ctl_verification

   Examples:
   Here are some example sequences of the VIS executions using the approximate
   model checker.

   read_blif_mv abp/abp.mv
   flatten_hierarchy
   static_order
   build_partition_mdds
   set amc_sizeof_group 4
   approximate_model_check abp/abpt.ctl
   time
   quit

   read_blif_mv coherence/coherence.mv
   flatten_hierarchy
   static_order
   build_partition_mdds
   set amc_sizeof_group 8
   set amc_prove_false
   set amc_DC_level 0
   approximate_model_check coherence/coherence2.ctl
   time
   quit

   The algorithm used by approximate_model_check is described in detail in
   [7]ftp://vlsi.colorado.edu/pub/iccad96.ps
     _________________________________________________________________

   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/html/approximate_model_checkCmd.html#environment
   3. file://localhost/projects/development/hsv/vis/common/doc/ctl/ctl/ctl.html
   4. file://localhost/projects/development/hsv/vis/common/doc/html/approximate_model_checkCmd.html#sizeofgroup
   5. file://localhost/projects/development/hsv/vis/common/doc/html/model_checkCmd.html
   6. file://localhost/projects/development/hsv/vis/common/doc/html/read_fairnessCmd.html
   7. ftp://vlsi.colorado.edu/pub/iccad96.ps