you have your argument between ').
Another solution is to use the ``<config>`` tag in the platform file. The
-only restriction is that this tag must occure before the first
+only restriction is that this tag must occur before the first
platform element (be it ``<zone>``, ``<cluster>``, ``<peer>`` or whatever).
The ``<config>`` tag takes an ``id`` attribute, but it is currently
ignored so you don't really need to pass it. The important part is that
- **For collective operations of SMPI,** please refer to Section :ref:`cfg=smpi/coll-selector`
- **smpi/async-small-thresh:** :ref:`cfg=smpi/async-small-thresh`
+- **smpi/buffering:** :ref:`cfg=smpi/buffering`
- **smpi/bw-factor:** :ref:`cfg=smpi/bw-factor`
- **smpi/coll-selector:** :ref:`cfg=smpi/coll-selector`
- **smpi/comp-adjustment-file:** :ref:`cfg=smpi/comp-adjustment-file`
network card. Three models exists, but actually, only 2 of them are
interesting. The "compound" one is simply due to the way our
internal code is organized, and can easily be ignored. So at the
- end, you have two host models: The default one allows to aggregate
+ end, you have two host models: The default one allows aggregation of
an existing CPU model with an existing network model, but does not
allow parallel tasks because these beasts need some collaboration
between the network and CPU model. That is why, ptask_07 is used by
.. _cfg=smpi/async-small-thresh:
-Simulating Asyncronous Send
-^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Simulating Asynchronous Send
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-(this configuration item is experimental and may change or disapear)
+(this configuration item is experimental and may change or disappear)
It is possible to specify that messages below a certain size will be
sent as soon as the call to MPI_Send is issued, without waiting for
this mailbox will have this behavior regardless of the message size.
This value needs to be smaller than or equals to the threshold set at
-@ref options_model_smpi_detached , because asynchronous messages are
-meant to be detached as well.
+:ref:`cfg=smpi/send-is-detached-thresh`, because asynchronous messages
+are meant to be detached as well.
.. _options_pls:
Activating Plugins
------------------
-SimGrid plugins allow to extend the framework without changing its
+SimGrid plugins allow one to extend the framework without changing its
source code directly. Read the source code of the existing plugins to
learn how to do so (in ``src/plugins``), and ask your questions to the
usual channels (Stack Overflow, Mailing list, IRC). The basic idea is
Safety properties are expressed as assertions using the function
:cpp:func:`void MC_assert(int prop)`.
+.. _cfg=smpi/buffering:
+
+Specifying the MPI buffering behavior
+.....................................
+
+**Option** ``smpi/buffering`` **Default:** infty
+
+Buffering in MPI has a huge impact on the communication semantic. For example,
+standard blocking sends are synchronous calls when the system buffers are full
+while these calls can complete immediately without even requiring a matching
+receive call for small messages sent when the system buffers are empty.
+
+In SMPI, this depends on the message size, that is compared against two thresholds:
+
+- if (size < :ref:`smpi/async-small-thresh <cfg=smpi/async-small-thresh>`) then
+ MPI_Send returns immediately, even if the corresponding receive has not be issued yet.
+- if (:ref:`smpi/async-small-thresh <cfg=smpi/async-small-thresh>` < size < :ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>`) then
+ MPI_Send returns as soon as the corresponding receive has been issued. This is known as the eager mode.
+- if (:ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>` < size) then
+ MPI_Send returns only when the message has actually been sent over the network. This is known as the rendez-vous mode.
+
+The ``smpi/buffering`` option gives an easier interface to choose between these semantics. It can take two values:
+
+- **zero:** means that buffering should be disabled. Blocking communications are actually blocking.
+- **infty:** means that buffering should be made infinite. Blocking communications are non-blocking.
+
.. _cfg=model-check/property:
Specifying a liveness property
If you want to specify liveness properties, you have to pass them on
the command line, specifying the name of the file containing the
-property, as formatted by the ltl2ba program.
-
+property, as formatted by the ltl2ba program. Note that ltl2ba is not
+part of SimGrid and must be installed separatly.
.. code-block:: shell
Size of Cycle Detection Set
...........................
-In order to detect cycles, the model-checker needs to check if a new
+In order to detect cycles, the model checker needs to check if a new
explored state is in fact the same state than a previous one. For
-that, the model-checker can take a snapshot of each visited state:
+that, the model checker can take a snapshot of each visited state:
this snapshot is then used to compare it with subsequent states in the
exploration graph.
.......................
The ``model-checker/max-depth`` can set the maximum depth of the
-exploration graph of the model-checker. If this limit is reached, a
+exploration graph of the model checker. If this limit is reached, a
logging message is sent and the results might not be exact.
By default, there is not depth limit.
Handling of Timeouts
....................
-By default, the model-checker does not handle timeout conditions: the `wait`
+By default, the model checker does not handle timeout conditions: the `wait`
operations never time out. With the ``model-check/timeout`` configuration item
-set to **yes**, the model-checker will explore timeouts of `wait` operations.
+set to **yes**, the model checker will explore timeouts of `wait` operations.
.. _cfg=model-check/communications-determinism:
.. _cfg=model-check/send-determinism:
The ``model-check/communications-determinism`` and
``model-check/send-determinism`` items can be used to select the
-communication determinism mode of the model-checker which checks
+communication determinism mode of the model checker which checks
determinism properties of the communications of an application.
Verification Performance Considerations
.. _cfg=model-check/replay:
-Replaying buggy execution paths out of the model-checker
-........................................................
+Replaying buggy execution paths from the model checker
+......................................................
-Debugging the problems reported by the model-checker is challenging: First, the
+Debugging the problems reported by the model checker is challenging: First, the
application under verification cannot be debugged with gdb because the
-model-checker already traces it. Then, the model-checker may explore several
+model checker already traces it. Then, the model checker may explore several
execution paths before encountering the issue, making it very difficult to
understand the outputs. Fortunately, SimGrid provides the execution path leading
to any reported issue so that you can replay this path out of the model checker,
enabling the usage of classical debugging tools.
-When the model-checker finds an interesting path in the application
+When the model checker finds an interesting path in the application
execution graph (where a safety or liveness property is violated), it
generates an identifier for this path. Here is an example of output:
[ 0.000000] (0:@) Executed transitions = 46
The interesting line is ``Path = 1/3;1/4``, which means that you should use
-`--cfg=model-check/replay:1/3;1/4`` to replay your application on the buggy
-execution path. The other options should be the same (but the model-checker
-should be disabled). Note that format and meaning of the path may change between
-different releases.
+``--cfg=model-check/replay:1/3;1/4`` to replay your application on the buggy
+execution path. All options (but the model checker related ones) must
+remain the same. In particular, if you ran your application with
+``smpirun -wrapper simgrid-mc``, then do it again. Remove all
+MC-related options, keep the other ones and add
+``--cfg=model-check/replay``.
+
+Currently, if the path is of the form ``X;Y;Z``, each number denotes
+the actor's pid that is selected at each indecision point. If it's of
+the form ``X/a;Y/b``, the X and Y are the selected pids while the a
+and b are the return values of their simcalls. In the previouse
+example, ``1/3;1/4``, you can see from the full output that the actor
+1 is doing MC_RANDOM simcalls, so the 3 and 4 simply denote the values
+that these simcall return.
Configuring the User Code Virtualization
----------------------------------------
The main reason to change this setting is when the debugging tools get
fooled by the optimized context factories. Threads are the most
-debugging-friendly contextes, as they allow to set breakpoints
+debugging-friendly contexts, as they allow one to set breakpoints
anywhere with gdb and visualize backtraces for all processes, in order
to debug concurrency issues. Valgrind is also more comfortable with
threads, but it should be usable with all factories (Exception: the
as 16 KiB, for example. This *setting is ignored* when using the
thread factory. Instead, you should compile SimGrid and your
application with ``-fsplit-stack``. Note that this compilation flag is
-not compatible with the model-checker right now.
+not compatible with the model checker right now.
The operating system should only allocate memory for the pages of the
stack which are actually used and you might not need to use this in
If you are using the **ucontext** or **raw** context factories, you can
request to execute the user code in parallel. Several threads are
-launched, each of them handling as much user contexts at each run. To
-actiave this, set the ``contexts/nthreads`` item to the amount of
-cores that you have in your computer (or lower than 1 to have
-the amount of cores auto-detected).
+launched, each of them handling the same number of user contexts at each
+run. To activate this, set the ``contexts/nthreads`` item to the amount
+of cores that you have in your computer (or lower than 1 to have the
+amount of cores auto-detected).
Even if you asked several worker threads using the previous option,
you can request to start the parallel execution (and pay the
this code, and create an execution task within the simulator to take
this into account. For that, the actual duration is measured on the
host machine and then scaled to the power of the corresponding
-simulated machine. The variable ``smpi/host-speed`` allows to specify
+simulated machine. The variable ``smpi/host-speed`` allows one to specify
the computational speed of the host machine (in flop/s) to use when
scaling the execution times. It defaults to 20000, but you really want
to update it to get accurate simulation results.
possible to avoid this, as described in the main `SMPI publication
<https://hal.inria.fr/hal-01415484>`_ and in the :ref:`SMPI
documentation <SMPI_what_globals>`. SimGrid provides two ways of
-automatically privatizing the globals, and this option allows to
+automatically privatizing the globals, and this option allows one to
choose between them.
- **no** (default when not using smpirun): Do not automatically
This threshold specifies the size in bytes under which the send will
return immediately. This is different from the threshold detailed in
-:ref:`options_model_network_asyncsend` because the message is not
+:ref:`cfg=smpi/async-small-thresh` because the message is not
effectively sent when the send is posted. SMPI still waits for the
correspondant receive to be posted to perform the communication
operation.
for each shared bloc.
With the ``global`` algorithm, each call to SMPI_SHARED_MALLOC()
-returns a new adress, but it only points to a shadow bloc: its memory
+returns a new address, but it only points to a shadow bloc: its memory
area is mapped on a 1MiB file on disk. If the returned bloc is of size
N MiB, then the same file is mapped N times to cover the whole bloc.
At the end, no matter how many SMPI_SHARED_MALLOC you do, this will
