- **host/model:** :ref:`options_model_select`
-- **maxmin/precision:** :ref:`cfg=maxmin/precision`
- **maxmin/concurrency-limit:** :ref:`cfg=maxmin/concurrency-limit`
- **model-check:** :ref:`options_modelchecking`
-- **model-check/checkpoint:** :ref:`cfg=model-check/checkpoint`
- **model-check/communications-determinism:** :ref:`cfg=model-check/communications-determinism`
- **model-check/dot-output:** :ref:`cfg=model-check/dot-output`
- **model-check/max-depth:** :ref:`cfg=model-check/max-depth`
-- **model-check/property:** :ref:`cfg=model-check/property`
- **model-check/reduction:** :ref:`cfg=model-check/reduction`
- **model-check/replay:** :ref:`cfg=model-check/replay`
- **model-check/send-determinism:** :ref:`cfg=model-check/send-determinism`
- **model-check/setenv:** :ref:`cfg=model-check/setenv`
-- **model-check/termination:** :ref:`cfg=model-check/termination`
- **model-check/timeout:** :ref:`cfg=model-check/timeout`
-- **model-check/visited:** :ref:`cfg=model-check/visited`
- **network/bandwidth-factor:** :ref:`cfg=network/bandwidth-factor`
- **network/crosstraffic:** :ref:`cfg=network/crosstraffic`
- **storage/max_file_descriptors:** :ref:`cfg=storage/max_file_descriptors`
-- **surf/precision:** :ref:`cfg=surf/precision`
+- **precision/timing:** :ref:`cfg=precision/timing`
+- **precision/work-amount:** :ref:`cfg=precision/work-amount`
- **For collective operations of SMPI,** please refer to Section :ref:`cfg=smpi/coll-selector`
- **smpi/auto-shared-malloc-thresh:** :ref:`cfg=smpi/auto-shared-malloc-thresh`
simulators as network models (see :ref:`models_ns3`).
This model can be :ref:`further configured <options_pls>`.
-- ``cpu/model``: specify the used CPU model. We have only one model
- for now:
+- ``cpu/model``: specify the used CPU model. We have only one model for now:
- **Cas01:** Simplistic CPU model (time=size/speed)
-- ``host/model``: The host concept is the aggregation of a CPU with a
- 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 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.
-
- - **default:** Default host model. Currently, CPU:Cas01 and
- network:LV08 (with cross traffic enabled)
- - **compound:** Host model that is automatically chosen if
- you change the network and CPU models
- - **ptask_L07:** Host model somehow similar to Cas01+CM02 but
- allowing "parallel tasks", that are intended to model the moldable
- tasks of the grid scheduling literature.
+- ``host/model``: we have two such models for now.
+
+ - **default:** Default host model. It simply uses the otherwise configured models for cpu, disk and network (i.e. CPU:Cas01,
+ disk:S19 and network:LV08 by default)
+ - **ptask_L07:** This model is mandatory if you plan to use parallel tasks (and useless otherwise). ptasks are intended to
+ model the moldable tasks of the grid scheduling literature. A specific host model is necessary because each such activity
+ has a both compute and communicate components, so the CPU and network models must be mixed together.
- ``storage/model``: specify the used storage model. Only one model is
provided so far.
The different models rely on a linear inequalities solver to share
the underlying resources. SimGrid allows you to change the solver, but
be cautious, **don't change it unless you are 100% sure**.
-
+
- items ``cpu/solver``, ``network/solver``, ``disk/solver`` and ``host/solver``
allow you to change the solver for each model:
and slow pattern that follows the actual dependencies.
.. _cfg=bmf/precision:
-.. _cfg=maxmin/precision:
-.. _cfg=surf/precision:
+.. _cfg=precision/timing:
+.. _cfg=precision/work-amount:
Numerical Precision
...................
-**Option** ``maxmin/precision`` **Default:** 1e-5 (in flops or bytes) |br|
-**Option** ``surf/precision`` **Default:** 1e-9 (in seconds) |br|
+**Option** ``precision/timing`` **Default:** 1e-9 (in seconds) |br|
+**Option** ``precision/work-amount`` **Default:** 1e-5 (in flops or bytes) |br|
**Option** ``bmf/precision`` **Default:** 1e-12 (no unit)
The analytical models handle a lot of floating point values. It is
**Option** ``network/weight-S`` **Default:** depends on the model
Value used to account for RTT-unfairness when sharing a bottleneck (network connections with a large RTT are generally penalized
-against those with a small one). Described in `Accuracy Study and Improvement of Network Simulation in the SimGrid Framework
-<http://mescal.imag.fr/membres/arnaud.legrand/articles/simutools09.pdf>`_
+against those with a small one). See :ref:`models_TCP` and also this scientific paper: `Accuracy Study and Improvement of Network
+Simulation in the SimGrid Framework <http://mescal.imag.fr/membres/arnaud.legrand/articles/simutools09.pdf>`_
Default values for ``CM02`` is 0. ``LV08`` sets it to 20537 while both ``SMPI`` and ``IB`` set it to 8775.
InfiniBand network behavior can be modeled through 3 parameters
``smpi/IB-penalty-factors:"βe;βs;γs"``, as explained in `the PhD
-thesis of Jean-Marc Vincent
+thesis of Jérôme Vienne
<http://mescal.imag.fr/membres/jean-marc.vincent/index.html/PhD/Vienne.pdf>`_ (in French)
or more concisely in `this paper <https://hal.inria.fr/hal-00953618/document>`_,
even if that paper does only describe models for myrinet and ethernet.
Configuring ns-3
^^^^^^^^^^^^^^^^
-**Option** ``ns3/TcpModel`` **Default:** "default" (ns-3 default)
+**Option** ``ns3/NetworkModel`` **Default:** "default" (ns-3 default TCP)
-When using ns-3, there is an extra item ``ns3/TcpModel``, corresponding
-to the ``ns3::TcpL4Protocol::SocketType`` configuration item in
-ns-3. The only valid values (enforced on the SimGrid side) are
-'default' (no change to the ns-3 configuration), 'NewReno' or 'Reno' or
-'Tahoe'.
+When using ns-3, the item ``ns3/NetworkModel`` can be used to switch between TCP or UDP, and switch the used TCP variante. If
+the item is left unchanged, ns-3 uses the default TCP implementation. With a value of "UDP", ns-3 is set to use UDP instead.
+With the value of either 'NewReno' or 'Cubic', the ``ns3::TcpL4Protocol::SocketType`` configuration item in ns-3 is set to the
+corresponding protocol.
**Option** ``ns3/seed`` **Default:** "" (don't set the seed in ns-3)
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.
+ MPI_Send returns immediately, and the message is sent even if the
+ corresponding receive has not be issued yet. This is known as the eager mode.
+- 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 also returns immediately, but SMPI waits for the corresponding
+ receive to be posted, in order to perform the communication operation.
- 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.
- **zero:** means that buffering should be disabled. All communications are actually blocking.
- **infty:** means that buffering should be made infinite. All communications are non-blocking.
-.. _cfg=model-check/property:
-
-Specifying a liveness property
-..............................
-
-**Option** ``model-check/property`` **Default:** unset
-
-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 <https://github.com/utwente-fmt/ltl2ba>`_ program.
-Note that ltl2ba is not part of SimGrid and must be installed separately.
-
-.. code-block:: console
-
- $ simgrid-mc ./my_program --cfg=model-check/property:<filename>
-
-.. _cfg=model-check/checkpoint:
-
-Going for Stateful Verification
-...............................
-
-By default, the system is backtracked to its initial state to explore
-another path, instead of backtracking to the exact step before the fork
-that we want to explore (this is called stateless verification). This
-is done this way because saving intermediate states can rapidly
-exhaust the available memory. If you want, you can change the value of
-the ``model-check/checkpoint`` item. For example,
-``--cfg=model-check/checkpoint:1`` asks to take a checkpoint every
-step. Beware, this will certainly explode your memory. Larger values
-are probably better, make sure to experiment a bit to find the right
-setting for your specific system.
-
.. _cfg=model-check/reduction:
Specifying the kind of reduction
................................
+**Option** model-check/reduction **Default:** "dpor"
+
The main issue when using the model-checking is the state space
explosion. You can activate some reduction technique with
``--cfg=model-check/reduction:<technique>``. For now, this
configuration variable can take 2 values:
- - **none:** Do not apply any kind of reduction (mandatory for
- liveness properties, as our current DPOR algorithm breaks cycles)
- - **dpor:** Apply Dynamic Partial Ordering Reduction. Only valid if
- you verify local safety properties (default value for safety
- checks).
-
-Another way to mitigate the state space explosion is to search for
-cycles in the exploration with the :ref:`cfg=model-check/visited`
-configuration. Note that DPOR and state-equality reduction may not
-play well together. You should choose between them.
+ - **none:** Do not apply any kind of reduction
+ - **dpor:** Apply Dynamic Partial Ordering Reduction. Only valid if you verify local safety properties (default value for
+ safety checks).
+ - **sdpor:** Source-set DPOR, as described in "Source Sets: A Foundation for Optimal Dynamic Partial Order Reduction"
+ by Abdulla et al.
+ - **odpor:** Optimal DPOR, as described in "Source Sets: A Foundation for Optimal Dynamic Partial Order Reduction"
+ by Abdulla et al.
Our current DPOR implementation could be improved in may ways. We are
currently improving its efficiency (both in term of reduction ability
-and computational speed), and future work could make it compatible
-with liveness properties.
-
-.. _cfg=model-check/visited:
-
-Size of Cycle Detection Set (state equality reduction)
-......................................................
-
-Mc SimGrid can be asked to search for cycles during the exploration,
-i.e. situations where a new explored state is in fact the same state
-than a previous one.. This can prove useful to mitigate the state
-space explosion with safety properties, and this is the crux when
-searching for counter-examples to the liveness properties.
+and computational speed).
-Note that this feature may break the current implementation of the
-DPOR reduction technique.
+.. _cfg=model-check/strategy:
-The ``model-check/visited`` item is the maximum number of states, which
-are stored in memory. If the maximum number of snapshotted state is
-reached, some states will be removed from the memory and some cycles
-might be missed. Small values can lead to incorrect verifications, but
-large values can exhaust your memory and be CPU intensive as each new
-state must be compared to that amount of older saved states.
-
-The default settings depend on the kind of exploration. With safety
-checking, no state is snapshotted and cycles cannot be detected. With
-liveness checking, all states are snapshotted because missing a cycle
-could hinder the exploration soundness.
-
-.. _cfg=model-check/termination:
-
-Non-Termination Detection
-.........................
+Guiding strategy
+................
-The ``model-check/termination`` configuration item can be used to
-report if a non-termination execution path has been found. This is a
-path with a cycle, which means that the program might never terminate.
+**Option** model-check/strategy **Default:** "none"
-This only works in safety mode, not in liveness mode.
+Even after the DPOR's reduction, the state space that we have to explore remains huge. SimGrid provides several guiding
+strategies aiming at converging faster toward bugs. By default, none of these strategy is enabled, and SimGrid does a regular
+DFS exploration.
-This options is disabled by default.
+ - **max_match_comm**: Try to minimize the number of in-fly communication by appairing matching send and receive. This tend to
+ produce nicer backtraces, in particular when a user-level ``send`` is broken down internally into a ``send_async`` + ``wait``.
+ This strategy will ensure that the ``wait`` occures as soon as possible, easing the understanding of the user who do not
+ expect her ``send`` to be split.
+ - **min_match_comm**: Try to maximize the number of in-fly communication by not appairing matching send and receive. This is
+ the exact opposite strategy, but it is still useful as it tend to explore first the branches where the risk of deadlock is
+ higher.
+ - **uniform**: this is a boring random strategy where choices are based on a uniform sampling of possible choices.
+ Surprisingly, it gives really really good results.
.. _cfg=model-check/dot-output:
If set, the ``model-check/dot-output`` configuration item is the name
of a file in which to write a dot file of the path leading to the
-property violation discovered (safety or liveness violation), as well
-as the cycle for liveness properties. This dot file can then be fed to the
+property violation discovered (safety violation). This dot file can then be fed to the
graphviz dot tool to generate a corresponding graphical representation.
.. _cfg=model-check/max-depth:
debugging tools.
When the model checker finds an interesting path in the application
-execution graph (where a safety or liveness property is violated), it
+execution graph (where a safety property is violated), it
generates an identifier for this path. Here is an example of the output:
.. code-block:: console
Configuring SMPI
----------------
-The SMPI interface provides several specific configuration items.
+The SMPI interface provides several specific configuration items.
These are not easy to see with ``--help-cfg``, since SMPI binaries are usually launched through the ``smiprun`` script.
.. _cfg=smpi/host-speed:
select the decision logic either of the OpenMPI or the MPICH libraries. (By
default SMPI uses naive version of collective operations.)
-Each collective operation can be manually selected with a
-``smpi/collective_name:algo_name``. Available algorithms are listed in
-:ref:`SMPI_use_colls`.
-
-.. TODO:: All available collective algorithms will be made available
- via the ``smpirun --help-coll`` command.
+Each collective operation can be manually selected with a ``smpi/collective_name:algo_name``. For example, if you want to use
+the Bruck algorithm for the Alltoall algorithm, you should use ``--cfg=smpi/alltoall:bruck`` on the command-line of smpirun. The
+reference of all available algorithms are listed in :ref:`SMPI_use_colls`, and you can get the full list implemented in your
+version using ``smpirun --help-coll``.
.. _cfg=smpi/barrier-collectives:
