VERIFY(1) Local Manual VERIFY(1)

NAME

verify — model-check a system of communicating machines

SYNOPSIS

verify [option ...] [scm-file]

DESCRIPTION

The verify tool reads the model given in the specified scm-file and model-checks it. If scm-file is omitted, the model is read from the standard input.

The model contains the description of a system of communicating machines along with, optionally, the specification of a set of bad configurations. See scm(5) for a description of the scm input language.

Upon succesful termination, verify either reports that the model is safe (if no bad configuration is reachable), or provides a counter-example trace (leading to some bad configuration).

Note that, depending on the input model and on the options that are used, verify may abort, or compute indefinitely. This problem cannot be avoided due to the undecidability of the model-checking problem for systems of communicating machines.

OPTIONS

Main Options

-mc-engine engine
Specifies the main algorithm used for model-checking. The following engines are available:
absint
Static analysis based on abstract interpretation.
armc
Abstract regular model-checking.
cegar
Counter-example guided abstraction refinement. This algorithm maintains an abstract graph whose nodes form a partition of the model's configuration space. Refinement consists in splitting abstract nodes visited by a spurious counter-example, according to a generated trace invariant. This is the default.
lart
Lazy abstraction refinement tree. This algorithm builds an abstract reachability tree, and maintains node covering information to truncate the tree. Branches leading to bad configurations are refined by strengthening nodes according to a generated trace invariant.
-tc-engine engine
Specifies the trace-checking algorithm used by some model-checkers. Here, trace-checking consists in analyzing a given abstract counter-example to determine whether it is feasible or spurious, and, in the latter case, provide a trace invariant “explaining” spuriousness. The following engines are available:
apinv-bwd
Perform an adaptive extrapolated symbolic pre computation along the abstract counter-example, starting from the failure abstract node. This is the default.
apinv-fwd
Reversed version of apinv-bwd (uses post).
upinv-fwd
Perform a uniform extrapolated symbolic post computation along the abstract counter-example.
upinv-bwd
Reversed version of upinv-fwd (uses pre).
This option only impacts the cegar model-checking engine.
-k-min start
The extrapolation operator is parameterized by a non-negative integer k. This option specifies the starting value of k. The model/trace-checking algorithms first try with k = start (which produces the coarsest over-approximation) and then iteratively increase k until the analysis is precise enough (or k becomes greater than the bound specified by -k-max). The start must be a nonnegative integer. The default is 0.

As an exception (a hack), it is also possible to specify a start of -1 (see option -extrapolation below).

-k-max stop
Specifies the largest value that model/trace-checking algorithms may use for the extrapolation parameter k. The stop must be a nonnegative integer. The default is 2.
-tc-discard-states
Removes abstract states from the trace before passing it to the trace-checking engine. With this option, abstract counter-examples are more likely to be feasible. But, for spurious counter-examples, trace invariant generation may require more precision (i.e., a higher extrapolation parameter).
-tc-validate
Validates each result provided by the trace-checking engine, and print an error message when validation fails.
-limit limit
Limit the number of model-checker iterations to limit. Note that iterations are not comparable between model-checking engines. The limit must be a nonnegative integer. OCaml's max_int is used by default.
-no-validation
The model-checking engine returns either a safe inductive invariant, or a counter-example trace. By default, this result is validated by a simple, independent algorithm. This option disables this validation.
-statistics
Upon succesful termination, verify displays detailed statistics about execution time and memory consumption.

Scm Wrapper Options

-scm-rel method
The symbolic one-step binary reachability relation of the model is not (directly) provided by the Scm library. This option specifies the method used to compute this binary relation. The following methods are supported:
post
Use the symbolic post operator of the Scm library.
pre
Use the symbolic pre operator of the Scm library.
mixed
Use post for send actions and pre for receive actions. This is the default.
-extrapolation operator
Specifies the extrapolation operator used for over-approximation of queue decision diagrams. The over-approximations provided by the Scm library are based on state equivalences. The following extrapolation operators are available:
bisim-fwd
Forward k-depth bisimulation equivalence. This is the default.
bisim-bwd
Backward k-depth bisimulation equivalence.
bisim-both
Conjunction of the two previous equivalences.
lang-fwd
Forward k-depth language equivalence.
lang-bwd
Backward k-depth language equivalence.
lang-both
Conjunction of the two previous equivalences.
identity
Identity function (no over-approximation).

As an exception, the extrapolation for k = -1 is the same for all operators, and consists in merging all states of the queue decision diagram. In other words, this extrapolation is equal to the 0-depth bisimulation/language equivalence without state coloring.

-extrapol-coloring coloring
Specifies the state coloring applied by the extrapolation operator on queue decision diagrams. The state equivalence induced by this coloring defines the 0-depth equivalence (see -extrapolation). The following state colorings are available:
final
Distinguish final states from the others (2 colors).
init
Distinguish initial states from the others (2 colors).
both
Conjunction of the two previous equivalences (4 colors).
none
Merge all states (1 color).
auto
Behave as final for forward extrapolations, as init for backward extrapolations, and as both for extrapolations that use both directions. This is the default.
-channel-policy policy
Channels in an scm model can be either perfect or lossy (see scm(5)). This option allows to override the reliability policy of the channels. The following reliability policies are supported:
all-lossy
Make all channels lossy.
all-perfect
Make all channels perfect.
normal
Keep the policy specified in the scm input. This is the default.

Cegar Options

-graph-exploration search
Specifies the exploration algorithm used to find a counter-example in the abstract graph. The following graph search algorithms are supported:
fwd-dfs
Forward depth-first search.
fwd-bfs
Forward breadth-first search.
bwd-dfs
Backward depth-first search.
bwd-bfs
Backward breadth-first search.
mixed
Use only breadth-first search and select the direction with the smallest set of initial nodes. This is the default.
-graph-refinement method
When an abstract node is split into n refined nodes, the abstract edges that enter or leave this node must be refined. This option specifies the method used to compute the refined edges. The following methods are supported:
rel
Use the model's symbolic one-step binary reachability relation rel. This method requires, for each edge refinement, n rel computations.
post-pre
Use the model's symbolic post and pre operators. This method requires, for each edge refinement, 1 post/pre computation and n emptiness tests. This is the default.

Lazy Abstraction Options

-tree-exploration exploration
Specifies the exploration strategy used to build the abstract reachability tree. The following exploration strategies are supported:
dfs
Depth-first exploration.
bfs
Breadth-first exploration. This is the default.
-no-tree-pruning
By default, nodes being refined with an empty region are removed from the tree. This option disables this pruning.

APInv Options

-safe-approximation algorithm
Adaptive trace invariant generation relies on a simplification procedure that, given a pair (r1, r2) of disjoint regions, returns an over-approximation of r1 that is still disjoint from r2. This option selects the algorithm used for the computation of this safe over-approximation. The following algorithms are available:
split
Given (r1, r2), return the extrapolation of r1 for the smallest parameter k that leads to an empty intersection with r2. This is the default.
co-split
Given (r1, r2), return the complement of the region obtained with split on (r2, r1).

Logging Options

-columns width
Use width columns for pretty-printing. In other words, set the value of the pretty-printer's right margin to width (in characters). The default is the value of the environment variable COLUMNS if set, or 78 otherwise.
-box-depth depth
Set the pretty-printer's box depth to depth. Boxes nested deeper than depth are printed as an ellipsis. OCaml's max_int is used by default.

SEE ALSO

control(1), scm(5)

AUTHORS

The verify tool is mainly written, maintained and tested by:

See the AUTHORS file in the source distribution for the full list of contributors.

Web site: ../../../projects/mcscm/wiki.html

CAVEATS

Numerical values held by messages or local variables are currently ignored by verify.
  • Conditions in transitions and bad configurations are discarded and assumed to be true.
  • Assignments in transitions are ignored.

These rules guarantee that the analysis performed by verify is “safety-conservative”.

BUGS

Please visit the following page for bug reports and feature requests: ../../../projects/mcscm/issues

ACKNOWLEDGEMENTS

The verify tool is programmed in Objective Caml and uses several 3rd-party libraries:
October 12, 2011 Linux 3.0.0-1-amd64