.TH SPIN 1
.SH NAME
spin \- verification tool for concurrent systems
.SH SYNOPSIS
.B spin
[
.BI -n N
]
[
.B -cplgrsmv
]
[
.B -iat
]
[
.B -V
]
[
.I file
]
.SH DESCRIPTION
.I Spin
is a tool for analyzing the logical consistency of
concurrent systems, specifically communication protocols.
The system is specified in a guarded command language called
.SM PROMELA\c
\&.
The language, described in the references,
allows for the dynamic creation of processes,
nondeterministic case selection, loops, gotos,
variables, and the specification of correctness requirements.
The tool has fast algorithms for analyzing arbitrary
liveness and safety conditions.
.PP
Given a model system specified in
.SM PROMELA\c
,
.I spin
can perform interactive, guided, or random simulations
of the system's execution
or it can generate a C program that performs an exhaustive
or approximate verification of the system.
The verifier can check, for instance, if user specified system
invariants are violated during a protocol's execution, or
if non-progress execution cycles exist.
.PP
Without any options the program performs a random simulation of the system
defined in the input
.IR file ,
default standard input.
The option
.BI -n N
sets the random seed to the integer value
.IR N .
.PP
The group of options
.B -pglmrsv
is used to set the level of information reported
about the simulation run.
Every line of output normally contains a reference to the source
line in the specification that caused it.
.TP
.B c
Show message send and receive operations in tabular form, but
no other information about the execution.
.TP
.B p
Show at each time step which process changed state and what source
statement was executed.
.TP
.B l
In combination with option
.BR p ,
show the current value of local variables of the process.
.TP
.B g
Show the value of global variables at each time step.
.TP
.B r
Show all message-receive events, giving
the name and number of the receiving process
and the corresponding source line number.
For each message parameter, show
the message type and the message channel number and name.
.TP
.B s
Show all message-send events.
.TP
.B m
Ordinarily, a send action will be delayed if the
target message buffer if full.
With this option a message sent to a full buffer is lost.
The option can be combined with
.B -a
(see below).
.TP
.B v
Verbose mode: add extra detail and include more warnings.
.TP
.BI i
Perform an interactive simulation.
.TP
.B a
Generate a protocol-specific verifier.
The output is written into a set of C files, named
.BR pan. [ cbhmt ],
that can be compiled
.RB ( "cc pan.c" )
to produce an executable verifier.
Systems that require more memory than available
on the target machine can still be analyzed by compiling
the verifier with a bit state space:
.IP
.B "   cc -DBITSTATE pan.c
.IP
This collapses the state space to 1 bit per system state,
with minimal side-effects.
Partial order reduction rules normally take effect during the
verification unless the compiler directive
.B -DNOREDUCE
is used.
.IP
The compiled verifiers have their own sets of options,
which can be seen by running them with option
.BR -? .
.TP
.B t
If the verifier finds a violation of a correctness property,
it writes an error trail.
The trail can be inspected in detail by invoking
.I spin
with the
.B -t
option.
In combination with the options
.BR pglrsv ,
different views of the error sequence are then be obtained.
.TP
.B V
Print the version number and exit.
.SH SOURCE
.B /sys/src/cmd/spin
.SH SEE ALSO
G.J. Holzmann,
.I
Design and Validation of Computer Protocols,
Prentice Hall, 1991.
.br
\(em, ``Using
.SM SPIN\c
\&''.