\verbatim
--cfg=model-check:1
\endverbatim
+
Safety properties are expressed as assertions using the function
\verbatim
void MC_assert(int prop);
so that you don't have to give <tt>--cfg=model-check:1</tt> in
addition.
+\subsection options_modelchecking_timeout Handling of timeout
+
+By default, the model-checker does not handle timeout conditions: the `wait`
+operations never time out. With the \b model-check/timeout configuration item
+set to \b yes, the model-checker will explore timeouts of `wait` operations.
+
+\subsection options_modelchecking_comm_determinism Communication determinism
+
+The \b model-check/communications_determinism and
+\b model-check/send_determinism items can be used to select the communication
+determinism mode of the model-checker which checks determinism properties of
+the communications of an application.
+
+\subsection options_modelchecking_sparse_checkpoint Per page checkpoints
+
+When the model-checker is configured to take a snapshot of each explored state
+(with the \b model-checker/visited item), the memory consumption can rapidly
+reach GiB ou Tib of memory. However, for many workloads, the memory does not
+change much between different snapshots and taking a complete copy of each
+snapshot is a waste of memory.
+
+The \b model-check/sparse-checkpoint option item can be set to \b yes in order
+to avoid making a complete copy of each snapshot: instead, each snapshot will be
+decomposed in blocks which will be stored separately.
+If multiple snapshots share the same block (or if the same block
+is used in the same snapshot), the same copy of the block will be shared leading
+to a reduction of the memory footprint.
+
+For many applications, this option considerably reduces the memory consumption.
+In somes cases, the model-checker might be slightly slower because of the time
+taken to manage the metadata about the blocks. In other cases however, this
+snapshotting strategy will be much faster by reducing the cache consumption.
+When the memory consumption is important, by avoiding to hit the swap or
+reducing the swap usage, this option might be much faster than the basic
+snapshotting strategy.
+
+This option is currently disabled by default.
+
\subsection options_mc_perf Performance considerations for the model checker
The size of the stacks can have a huge impact on the memory
-consumption when using model-checking. Currently each snapshot, will
-save a copy of the whole stack and not only of the part which is
+consumption when using model-checking. By default, each snapshot will
+save a copy of the whole stacks and not only of the part which is
really meaningful: you should expect the contribution of the memory
consumption of the snapshots to be \f$ \mbox{number of processes}
\times \mbox{stack size} \times \mbox{number of states} \f$.
-However, when compiled against the model checker, the stacks are not
+The \b model-check/sparse-checkpoint can be used to reduce the memory
+consumption by trying to share memory between the different snapshots.
+
+When compiled against the model checker, the stacks are not
protected with guards: if the stack size is too small for your
application, the stack will silently overflow on other parts of the
memory.
+\subsection options_modelchecking_hash Hashing of the state (experimental)
+
+Usually most of the time of the model-checker is spent comparing states. This
+process is complicated and consumes a lot of bandwidth and cache.
+In order to speedup the state comparison, the experimental \b model-checker/hash
+configuration item enables the computation of a hash summarizing as much
+information of the state as possible into a single value. This hash can be used
+to avoid most of the comparisons: the costly comparison is then only used when
+the hashes are identical.
+
+Currently most of the state is not included in the hash because the
+implementation was found to be buggy and this options is not as useful as
+it could be. For this reason, it is currently disabled by default.
+
+\subsection options_recordreplay Record/replay (experimental)
+
+As the model-checker keeps jumping at different places in the execution graph,
+it is difficult to understand what happens when trying to debug an application
+under the model-checker. Event the output of the program is difficult to
+interpret. Moreover, the model-checker does not behave nicely with advanced
+debugging tools such as valgrind. For those reason, to identify a trajectory
+in the execution graph with the model-checker and replay this trajcetory and
+without the model-checker black-magic but with more standard tools
+(such as a debugger, valgrind, etc.). For this reason, Simgrid implements an
+experimental record/replay functionnality in order to record a trajectory with
+the model-checker and replay it without the model-checker.
+
+When the model-checker finds an interesting path in the application execution
+graph (where a safety or liveness property is violated), it can generate an
+identifier for this path. In order to enable this behavious the
+\b model-check/record must be set to \b yes. By default, this behaviour is not
+enabled.
+
+This is an example of output:
+
+<pre>
+[ 0.000000] (0:@) Check a safety property
+[ 0.000000] (0:@) **************************
+[ 0.000000] (0:@) *** PROPERTY NOT VALID ***
+[ 0.000000] (0:@) **************************
+[ 0.000000] (0:@) Counter-example execution trace:
+[ 0.000000] (0:@) Path = 1/3;1/4
+[ 0.000000] (0:@) [(1)Tremblay (app)] MC_RANDOM(3)
+[ 0.000000] (0:@) [(1)Tremblay (app)] MC_RANDOM(4)
+[ 0.000000] (0:@) Expanded states = 27
+[ 0.000000] (0:@) Visited states = 68
+[ 0.000000] (0:@) Executed transitions = 46
+</pre>
+
+This path can then be replayed outside of the model-checker (and even in
+non-MC build of simgrid) by setting the \b model-check/replay item to the given
+path. The other options should be the same (but the model-checker should
+be disabled).
+
+The format and meaning of the path may change between different releases so
+the same release of Simgrid should be used for the record phase and the replay
+phase.
+
\section options_virt Configuring the User Process Virtualization
\subsection options_virt_factory Selecting the virtualization factory
application, the variable \b
smpi/simulation_computation should be set to no
-\subsection options_smpi_bw_factor smpi/bw_factor: Bandwidth factors
+\subsection options_model_smpi_bw_factor smpi/bw_factor: Bandwidth factors
The possible throughput of network links is often dependent on the
message sizes, as protocols may adapt to different message sizes. With
Simulation time: 1e3 seconds.
\endverbatim
-\subsection options_smpi_global Automatic privatization of global variables
+\subsection options_model_smpi_lat_factor smpi/lat_factor: Latency factors
+
+The motivation and syntax for this option is identical to the motivation/syntax
+of smpi/bw_factor, see \ref options_model_smpi_bw_factor for details.
+
+There is an important difference, though: While smpi/bw_factor \a reduces the
+actual bandwidth (i.e., values between 0 and 1 are valid), latency factors
+increase the latency, i.e., values larger than or equal to 1 are valid here.
+
+This is the default value:
+
+\verbatim
+65472:11.6436;15424:3.48845;9376:2.59299;5776:2.18796;3484:1.88101;1426:1.61075;732:1.9503;257:1.95341;0:2.01467
+\endverbatim
+
+\subsection options_smpi_global smpi/privatize_global_variables: Automatic privatization of global variables
MPI executables are meant to be executed in separated processes, but SMPI is
executed in only one process. Global variables from executables will be placed
uses naive version of collective operations). Each collective operation can be manually selected with a
\b smpi/collective_name:algo_name. Available algorithms are listed in \ref SMPI_collective_algorithms .
+\subsection options_model_smpi_iprobe smpi/iprobe: Inject constant times for calls to MPI_Iprobe
+
+\b Default value: 0.0001
+
+The behavior and motivation for this configuration option is identical with \a smpi/test, see
+Section \ref options_model_smpi_test for details.
+
+\subsection options_model_smpi_test smpi/test: Inject constant times for calls to MPI_Test
+
+\b Default value: 0.0001
+
+By setting this option, you can control the amount of time a process sleeps
+when MPI_Test() is called; this is important, because SimGrid normally only
+advances the time while communication is happening and thus,
+MPI_Test will not add to the time, resulting in a deadlock if used as a
+break-condition.
+
+Here is an example:
+
+\code{.unparsed}
+ while(!flag) {
+ MPI_Test(request, flag, status);
+ ...
+ }
+\endcode
+
+\note
+ Internally, in order to speed up execution, we use a counter to keep track
+ on how often we already checked if the handle is now valid or not. Hence, we
+ actually use counter*SLEEP_TIME, that is, the time MPI_Test() causes the process
+ to sleep increases linearly with the number of previously failed testk.
+
+
+\subsection options_model_smpi_wtime smpi/wtime: Inject constant times for calls to MPI_Wtime
+
+\b Default value: 0
+
+By setting this option, you can control the amount of time a process sleeps
+when MPI_Wtime() is called; this is important, because SimGrid normally only
+advances the time while communication is happening and thus,
+MPI_Wtime will not add to the time, resulting in a deadlock if used as a
+break-condition.
+
+Here is an example:
+
+\code{.unparsed}
+ while(MPI_Wtime() < some_time_bound) {
+ ...
+ }
+\endcode
+
+If the time is never advanced, this loop will clearly never end as MPI_Wtime()
+always returns the same value. Hence, pass a (small) value to the smpi/wtime
+option to force a call to MPI_Wtime to advance the time as well.
+
\section options_generic Configuring other aspects of SimGrid
for the moment (May 2015).
\note
- \b Please \b note: You can also pass the command-line option "\b--help" and
+ \b Please \b note: You can also pass the command-line option "\b --help" and
"--help-cfg" to an executable that uses simgrid.
- \c clean_atexit: \ref options_generic_clean_atexit
- \c model-check: \ref options_modelchecking
- \c model-check/checkpoint: \ref options_modelchecking_steps
- \c model-check/communications_determinism: \ref options_modelchecking_comm_determinism
+- \c model-check/communications_determinism: \ref options_modelchecking_send_determinism
- \c model-check/dot_output: \ref options_modelchecking_dot_output
- \c model-check/hash: \ref options_modelchecking_hash
- \c model-check/property: \ref options_modelchecking_liveness
- \c model-check/max_depth: \ref options_modelchecking_max_depth
-- \c model-check/record: \ref options_modelchecking_record
+- \c model-check/record: \ref options_modelchecking_recordreplay
- \c model-check/reduction: \ref options_modelchecking_reduction
-- \c model-check/replay: \ref options_modelchecking_replay
+- \c model-check/replay: \ref options_modelchecking_recordreplay
- \c model-check/send_determinism: \ref options_modelchecking_sparse_checkpoint
-- \c model-check/snapshot_fds: \ref options_modelchecking_snapshot_fds
- \c model-check/sparse-checkpoint: \ref options_modelchecking_sparse_checkpoint
- \c model-check/termination: \ref options_modelchecking_termination
- \c model-check/timeout: \ref options_modelchecking_timeout
