example, to set the item ``Item`` to the value ``Value``, simply
type the following on the command-line:
-.. code-block:: shell
+.. code-block:: console
- my_simulator --cfg=Item:Value (other arguments)
+ $ my_simulator --cfg=Item:Value (other arguments)
Several ``--cfg`` command line arguments can naturally be used. If you
need to include spaces in the argument, don't forget to quote the
</config>
A last solution is to pass your configuration directly in your program
-with :cpp:func:`simgrid::s4u::Engine::set_config` or :cpp:func:`MSG_config`.
+with :cpp:func:`simgrid::s4u::Engine::set_config`.
.. code-block:: cpp
option. For example, ``--cfg=plugin:help`` will give you the list
of plugins available in your installation of SimGrid.
+- **bmf/max-iterations:** :ref:`cfg=bmf/max-iterations`
+- **bmf/precision:** :ref:`cfg=bmf/precision`
+
- **contexts/factory:** :ref:`cfg=contexts/factory`
- **contexts/guard-size:** :ref:`cfg=contexts/guard-size`
- **contexts/nthreads:** :ref:`cfg=contexts/nthreads`
- **host/model:** :ref:`options_model_select`
-- **maxmin/precision:** :ref:`cfg=maxmin/precision`
- **maxmin/concurrency-limit:** :ref:`cfg=maxmin/concurrency-limit`
-- **msg/debug-multiple-use:** :ref:`cfg=msg/debug-multiple-use`
-
- **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/termination:** :ref:`cfg=model-check/termination`
+- **model-check/setenv:** :ref:`cfg=model-check/setenv`
- **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`
- **smpi/async-small-thresh:** :ref:`cfg=smpi/async-small-thresh`
+- **smpi/barrier-finalization:** :ref:`cfg=smpi/barrier-finalization`
+- **smpi/barrier-collectives:** :ref:`cfg=smpi/barrier-collectives`
- **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`
- **smpi/cpu-threshold:** :ref:`cfg=smpi/cpu-threshold`
- **smpi/display-allocs:** :ref:`cfg=smpi/display-allocs`
- **smpi/display-timing:** :ref:`cfg=smpi/display-timing`
- **smpi/errors-are-fatal:** :ref:`cfg=smpi/errors-are-fatal`
-- **smpi/finalization-barrier:** :ref:`cfg=smpi/finalization-barrier`
- **smpi/grow-injected-times:** :ref:`cfg=smpi/grow-injected-times`
- **smpi/host-speed:** :ref:`cfg=smpi/host-speed`
- **smpi/IB-penalty-factors:** :ref:`cfg=smpi/IB-penalty-factors`
- **smpi/iprobe-cpu-usage:** :ref:`cfg=smpi/iprobe-cpu-usage`
- **smpi/init:** :ref:`cfg=smpi/init`
- **smpi/keep-temps:** :ref:`cfg=smpi/keep-temps`
-- **smpi/lat-factor:** :ref:`cfg=smpi/lat-factor`
- **smpi/ois:** :ref:`cfg=smpi/ois`
- **smpi/or:** :ref:`cfg=smpi/or`
- **smpi/os:** :ref:`cfg=smpi/os`
- **smpi/papi-events:** :ref:`cfg=smpi/papi-events`
+- **smpi/pedantic:** :ref:`cfg=smpi/pedantic`
- **smpi/privatization:** :ref:`cfg=smpi/privatization`
- **smpi/privatize-libs:** :ref:`cfg=smpi/privatize-libs`
- **smpi/send-is-detached-thresh:** :ref:`cfg=smpi/send-is-detached-thresh`
<https://hal.inria.fr/inria-00071989/document>`_.
- **ns-3** (only available if you compiled SimGrid accordingly):
Use the packet-level network
- simulators as network models (see :ref:`model_ns3`).
+ 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. That is why, ptask_07 is used by
- default when using SimDag.
-
- - **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.
.. todo: make 'compound' the default host model.
+.. _options_model_solver:
+
+Solver
+......
+
+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:
+
+ - **maxmin:** The default solver for all models except ptask. Provides a
+ max-min fairness allocation.
+ - **fairbottleneck:** The default solver for ptasks. Extends max-min to
+ allow heterogeneous resources.
+ - **bmf:** More realistic solver for heterogeneous resource sharing.
+ Implements BMF (Bottleneck max fairness) fairness. To be used with
+ parallel tasks instead of fair-bottleneck.
+
.. _options_model_optim:
Optimization Level
..................
-The network and CPU models that are based on lmm_solve (that
+The network and CPU models that are based on linear inequalities solver (that
is, all our analytical models) accept specific optimization
configurations.
the dependency induced by the backbone), but through a complicated
and slow pattern that follows the actual dependencies.
-.. _cfg=maxmin/precision:
-.. _cfg=surf/precision:
+.. _cfg=bmf/precision:
+.. _cfg=precision/timing:
+.. _cfg=precision/work-amount:
Numerical Precision
...................
-**Option** ``maxmin/precision`` **Default:** 0.00001 (in flops or bytes) |br|
-**Option** ``surf/precision`` **Default:** 0.00001 (in seconds)
+**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
possible to change the epsilon used to update and compare them through
on highly constrained scenarios, but the simulation speed suffers of this
setting on regular (less constrained) scenarios so it is off by default.
+.. _cfg=bmf/max-iterations:
+
+BMF settings
+............
+
+**Option** ``bmf/max-iterations`` **Default:** 1000
+
+It may happen in some settings that the BMF solver fails to converge to
+a solution, so there is a hard limit on the amount of iteration count to
+avoid infinite loops.
+
.. _options_model_network:
Configuring the Network Model
**Option** ``network/TCP-gamma`` **Default:** 4194304
-The analytical models need to know the maximal TCP window size to take
-the TCP congestion mechanism into account. On Linux, this value can
-be retrieved using the following commands. Both give a set of values,
-and you should use the last one, which is the maximal size.
+The analytical models need to know the maximal TCP window size to take the TCP congestion mechanism into account (see
+:ref:`this page <understanding_cm02>` for details). On Linux, this value can be retrieved using the following commands.
+Both give a set of values, and you should use the last one, which is the maximal size.
-.. code-block:: shell
+.. code-block:: console
- cat /proc/sys/net/ipv4/tcp_rmem # gives the sender window
- cat /proc/sys/net/ipv4/tcp_wmem # gives the receiver window
+ $ cat /proc/sys/net/ipv4/tcp_rmem # gives the sender window
+ $ cat /proc/sys/net/ipv4/tcp_wmem # gives the receiver window
+
+If you want to disable the TCP windowing mechanism, set this parameter to 0.
.. _cfg=network/bandwidth-factor:
.. _cfg=network/latency-factor:
.. _cfg=network/weight-S:
-Correcting Important Network Parameters
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+Manual calibration factors
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+SimGrid can take network irregularities such as a slow startup or changing behavior depending on the message size into account.
+The values provided by default were computed a long time ago through data fitting one the timings of either packet-level
+simulators or direct experiments on real platforms. These default values should be OK for most users, but if simulation realism
+is really important to you, you probably want to recalibrate the models (i.e., devise sensible values for your specific
+settings). This section only describes how to pass new values to the models while the calibration process involved in the
+computation of these values is described :ref:`in the relevant chapter <models_calibration>`.
+
+We found out that many networking effects can be realistically accounted for with the three following correction factors. They
+were shown to be enough to capture slow-start effects, the different transmission modes of MPI systems (eager vs. rendez-vous
+mode), or the non linear effects of wifi sharing.
+
+**Option** ``network/latency-factor`` **Default:** 1.0, but overridden by most models
+
+This option specifies a multiplier to apply to the *physical* latency (i.e., the one described in the platform) of the set of
+links involved in a communication. The factor can either be a constant to apply to any communication, or it may depend on the
+message size. The ``CM02`` model does not use any correction factor, so the latency-factor remains to 1. The ``LV08`` model sets
+it to 13.01 to model slow-start, while the ``SMPI`` model has several possible values depending on the interval in which the
+message size falls. The default SMPI setting given below specifies for example that a message smaller than 257 bytes will get a
+latency multiplier of 2.01467 while a message whose size is in [15424, 65472] will get a latency multiplier of 3.48845. The
+``wifi`` model goes further and uses a callback in the program to compute the factor that must be non-linear in this case.
+
+This multiplier is applied to the latency computed from the platform, that is the sum of all link *physical* latencies over the
+:ref:`network path <platform_routing>` used by the considered communication, to derive the *effective* end-to-end latency.
+
+Constant factors are easy to express, but the interval-based syntax used in SMPI is somewhat complex. It expects a set of
+factors separated by semicolons, each of the form ``boundary:factor``. For example if your specification is
+``0:1;1000:2;5000:3``, it means that on [0, 1000) the factor is 1. On [1000,5000), the factor is 2 while the factor is 3 for
+5000 and beyond. If your first interval does include size=0, then the default value of 1 is used before. Changing the factor
+callback is not possible from the command line and must be done from your code, as shown in `this example
+<https://framagit.org/simgrid/simgrid/tree/master/examples/cpp/network-factors/s4u-network-factors.cpp>`_. Note that the chosen
+model only provides some default settings. You may pick a ``LV08`` model to get some of the settings, and override the latency
+with interval-based values.
+
+SMPI default value: 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 (interval boundaries are sorted automatically). These values were computed by data fitting on the Stampede
+Supercomputer at TACC, with optimal deployment of processes on nodes. To accurately model your settings, you should redo the
+:ref:`calibration <models_calibration>`.
+
+**Option** ``network/bandwidth-factor`` **Default:** 1.0, but overridden by most models
+
+Setting this option automatically adjusts the *effective* bandwidth (i.e., the one perceived by the application) used by any
+given communication. As with latency-factor above, the value can be a constant (``CM02`` uses 1 -- no correction -- while
+``LV08`` uses 0.97 to discount TCP headers while computing the payload bandwidth), interval-based (as the default provided by
+the ``SMPI``), or using in-program callbacks (as with ``wifi``).
+
+SMPI default value: 65472:0.940694;15424:0.697866;9376:0.58729;5776:1.08739;3484:0.77493;1426:0.608902;732:0.341987;257:0.338112;0:0.812084
+This was also computed on the Stampede Supercomputer.
+
+**Option** ``network/weight-S`` **Default:** depends on the model
-SimGrid can take network irregularities such as a slow startup or
-changing behavior depending on the message size into account. You
-should not change these values unless you really know what you're
-doing. The corresponding values were computed through data fitting
-one the timings of packet-level simulators, as described in `Accuracy
-Study and Improvement of Network Simulation in the SimGrid Framework
-<http://mescal.imag.fr/membres/arnaud.legrand/articles/simutools09.pdf>`_.
+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). 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.
-If you are using the SMPI model, these correction coefficients are
-themselves corrected by constant values depending on the size of the
-exchange. By default SMPI uses factors computed on the Stampede
-Supercomputer at TACC, with optimal deployment of processes on
-nodes. Again, only hardcore experts should bother about this fact.
+.. _cfg=network/loopback:
+Configuring loopback link
+^^^^^^^^^^^^^^^^^^^^^^^^^
-.. todo:: This section should be rewritten, and actually explain the
- options network/bandwidth-factor, network/latency-factor,
- network/weight-S.
+Several network models provide an implicit loopback link to account for local
+communication on a host. By default it has a 10GBps bandwidth and a null latency.
+This can be changed with ``network/loopback-lat`` and ``network/loopback-bw``
+items. Note that this loopback is conveniently modeled with a :ref:`single FATPIPE link <pf_loopback>`
+for the whole platform. If modeling contention inside nodes is important then you should
+rather add such loopback links (one for each host) yourself.
.. _cfg=smpi/IB-penalty-factors:
^^^^^^^^^^^^^^^^
InfiniBand network behavior can be modeled through 3 parameters
-``smpi/IB-penalty-factors:"βe;βs;γs"``, as explained in `this PhD
-thesis
+``smpi/IB-penalty-factors:"βe;βs;γs"``, as explained in `the PhD
+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.
You can see in Fig 2 some results for Infiniband, for example. This model
may be outdated by now for modern infiniband, anyway, so a new
-validation would be good.
+validation would be good.
The three paramaters are defined as follows:
To determine the penalty for a communication, two values need to be calculated. First, the penalty caused by the conflict in transmission, noted ps.
-- if ∆s (i) = 1 then ps = 1.
+- if ∆s (i) = 1 then ps = 1.
- if ∆s (i) ≥ 2 and ∆e (i) ≥ 3 then ps = ∆s (i) × βs × γr
-- else, ps = ∆s (i) × βs
+- else, ps = ∆s (i) × βs
Then, the penalty caused by the conflict in reception (noted pe) should be computed as follows:
- if ∆e (i) = 1 then pe = 1
-- else, pe = Φ (e) × βe × Ω (s, e)
+- else, pe = Φ (e) × βe × Ω (s, e)
Finally, the penalty associated with the communication is:
p = max (ps ∈ s, pe)
Note that with the default host model this option is activated by default.
-.. _cfg=network/loopback:
-
-Configuring loopback link
-^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Several network model provide an implicit loopback link to account for local
-communication on a host. By default it has a 10GBps bandwidth and a null latency.
-This can be changed with ``network/loopback-lat`` and ``network/loopback-bw``
-items.
-
.. _cfg=smpi/async-small-thresh:
Simulating Asynchronous Send
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-(this configuration item is experimental and may change or disappear)
-
It is possible to specify that messages below a certain size (in bytes) will be
sent as soon as the call to MPI_Send is issued, without waiting for
the correspondent receive. This threshold can be configured through
the ``smpi/async-small-thresh`` item. The default value is 0. This
behavior can also be manually set for mailboxes, by setting the
receiving mode of the mailbox with a call to
-:cpp:func:`MSG_mailbox_set_async`. After this, all messages sent to
+:cpp:func:`sg_mailbox_set_receiver`. After this, all messages sent to
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
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)
To enable SimGrid's model-checking support, the program should
be executed using the simgrid-mc wrapper:
-.. code-block:: shell
+.. code-block:: console
- simgrid-mc ./my_program
+ $ simgrid-mc ./my_program
Safety properties are expressed as assertions using the function
:cpp:func:`void MC_assert(int prop)`.
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:: shell
-
- 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.
+and computational speed).
-.. _cfg=model-check/visited:
+.. _cfg=model-check/strategy:
-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.
-
-Note that this feature may break the current implementation of the
-DPOR reduction technique.
-
-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:
communication determinism mode of the model checker, which checks
determinism properties of the communications of an application.
+.. _cfg=model-check/setenv:
+
+Passing environment variables
+.............................
+
+You can specify extra environment variables to be set in the verified application
+with ``model-check/setenv``. For example, you can preload a library as follows:
+``-cfg=model-check/setenv:LD_PRELOAD=toto;LD_LIBRARY_PATH=/tmp``.
+
.. _options_mc_perf:
Verification Performance Considerations
Replaying buggy execution paths from the model checker
......................................................
-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 execution paths before encountering the issue, making it
-very difficult to understand the output. Fortunately, SimGrid provides
+Debugging the problems reported by the model checker is challenging because
+the model checker may explore several execution paths before encountering the issue,
+the output very difficult to understand. Fortunately, SimGrid provides
the execution path leading to any reported issue so that you can replay
-this path reported by the model checker, enabling the usage of classical
-debugging tools.
+this path reported by the model checker, restoring a classical experience of debugging.
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:: shell
+.. code-block:: console
[ 0.000000] (0:@) Check a safety property
[ 0.000000] (0:@) **************************
``--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
+``smpirun -wrapper simgrid-mc``, then remove the ``-wrapper simgrid-mc`` part
+(you may want to use valgrind or gdb as wrappers instead). Also remove all
MC-related options, keep non-MC-related ones and add
``--cfg=model-check/replay:???``.
+Things are very similar if you are using sthread. Simply drop ``simgrid-mc`` from your command line, as follows:
+
+.. code-block:: console
+
+ $ LD_PRELOAD=../../lib/libsthread.so ./pthread-mutex-simpledeadlock --cfg=model-check/replay:'2;2;3;2;3;3'
+ sthread is intercepting the execution of ./pthread-mutex-simpledeadlock
+ [0.000000] [xbt_cfg/INFO] Configuration change: Set 'model-check/replay' to '2;2;3;2;3;3'
+ [0.000000] [mc_record/INFO] path=2;2;3;2;3;3
+ All threads are started.
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #1 '2/0' Actor thread 1(pid:2): MUTEX_ASYNC_LOCK(mutex_id:0 owner:none)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 1):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:26
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun1 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:21
+
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #2 '2/0' Actor thread 1(pid:2): MUTEX_WAIT(mutex_id:0 owner:2)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 1):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:29
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun1 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:21
+
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #3 '3/0' Actor thread 2(pid:3): MUTEX_ASYNC_LOCK(mutex_id:1 owner:none)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 2):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:26
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun2 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:31
+
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #4 '2/0' Actor thread 1(pid:2): MUTEX_ASYNC_LOCK(mutex_id:1 owner:3)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 1):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:26
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun1 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:22
+
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #5 '3/0' Actor thread 2(pid:3): MUTEX_WAIT(mutex_id:1 owner:3)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 2):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:29
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun2 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:31
+
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ [0.000000] [mc_record/INFO] * Path chunk #6 '3/0' Actor thread 2(pid:3): MUTEX_ASYNC_LOCK(mutex_id:0 owner:2)
+ [0.000000] [mc_record/INFO] ***********************************************************************************
+ Backtrace (displayed in actor thread 2):
+ -> #0 simgrid::s4u::Mutex::lock() at ../../src/s4u/s4u_Mutex.cpp:26
+ -> #1 sthread_mutex_lock at ../../src/sthread/sthread_impl.cpp:188
+ -> #2 pthread_mutex_lock at ../../src/sthread/sthread.c:141
+ -> #3 thread_fun2 at ../../examples/sthread/pthread-mutex-simpledeadlock.c:32
+
+ [0.000000] [mc_record/INFO] The replay of the trace is complete. DEADLOCK detected.
+ [0.000000] [ker_engine/INFO] 3 actors are still running, waiting for something.
+ [0.000000] [ker_engine/INFO] Legend of the following listing: "Actor <pid> (<name>@<host>): <status>"
+ [0.000000] [ker_engine/INFO] Actor 1 (main thread@Lilibeth) simcall ActorJoin(pid:2)
+ [0.000000] [ker_engine/INFO] Actor 2 (thread 1@Lilibeth) simcall MUTEX_WAIT(mutex_id:1 owner:3)
+ [0.000000] [ker_engine/INFO] Actor 3 (thread 2@Lilibeth) simcall MUTEX_WAIT(mutex_id:0 owner:2)
+ [0.000000] [sthread/INFO] All threads exited. Terminating the simulation.
+ [0.000000] ../../src/kernel/EngineImpl.cpp:265: [ker_engine/WARNING] Process called exit when leaving - Skipping cleanups
+ [0.000000] ../../src/kernel/EngineImpl.cpp:265: [ker_engine/WARNING] Process called exit when leaving - Skipping cleanups
+
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
auto-detection fails for you). They are approximately sorted here from
the slowest to the most efficient:
- - **thread:** very slow factory using full featured threads (either
- pthreads or windows native threads). They are slow but very
- standard. Some debuggers or profilers only work with this factory.
- - **java:** Java applications are virtualized onto java threads (that
- are regular pthreads registered to the JVM)
+ - **thread:** very slow factory using full featured, standard threads.
+ They are slow but very standard. Some debuggers or profilers only work with this factory.
- **ucontext:** fast factory using System V contexts (Linux and FreeBSD only)
- **boost:** This uses the `context
implementation <http://www.boost.org/doc/libs/1_59_0/libs/context/doc/html/index.html>`_
8192 (in KiB), while our Chord simulation works with stacks as small
as 16 KiB, for example. You can ensure that some actors have a specific
size by simply changing the value of this configuration item before
-creating these actors. The :cpp:func:`simgrid::s4u::Engine::set_config`
+creating these actors. The :cpp:func:`simgrid::s4u::Engine::set_config`
functions are handy for that.
This *setting is ignored* when using the thread factory (because there
Disabling Stack Guard Pages
...........................
-**Option** ``contexts/guard-size`` **Default** 1 page in most case (0 pages on Windows or with MC)
+**Option** ``contexts/guard-size`` **Default** 1 page in most case (0 pages with MC)
Unless you use the threads context factory (see
:ref:`cfg=contexts/factory`), a stack guard page is usually used
.............................
Parallel execution of the user code is only considered stable in
-SimGrid v3.7 and higher, and mostly for MSG simulations. SMPI
+SimGrid v3.7 and higher, and mostly for S4U simulations. SMPI
simulations may well fail in parallel mode. It is described in
`INRIA RR-7653 <http://hal.inria.fr/inria-00602216/>`_.
Configuring the Tracing
-----------------------
-The :ref:`tracing subsystem <outcomes_vizu>` can be configured in
-several different ways depending on the used interface (S4U, SMPI, SimDag)
+The :ref:`tracing subsystem <outcome_vizu>` can be configured in
+several different ways depending on the used interface (S4U, SMPI)
and the kind of traces that needs to be obtained. See the
:ref:`Tracing Configuration Options subsection
<tracing_tracing_options>` for a full description of each
you never used the tracing API.
-- Any SimGrid-based simulator (MSG, SimDag, SMPI, ...) and raw traces:
+- Any SimGrid-based simulator (S4U, SMPI, ...) and raw traces:
- .. code-block:: shell
+ .. code-block:: none
--cfg=tracing:yes --cfg=tracing/uncategorized:yes
tells it to trace host and link utilization (without any
categorization).
-- MSG or SimDag-based simulator and categorized traces (you need to
- declare categories and classify your tasks according to them)
+- S4U-based simulator and categorized traces (you need to
+ declare categories and classify your tasks according to them)
- .. code-block:: shell
+ .. code-block:: none
--cfg=tracing:yes --cfg=tracing/categorized:yes
- SMPI simulator and traces for a space/time view:
- .. code-block:: shell
+ .. code-block:: console
- smpirun -trace ...
+ $ smpirun -trace ...
The `-trace` parameter for the smpirun script runs the simulation
with ``--cfg=tracing:yes --cfg=tracing/smpi:yes``. Check the
- Add a string on top of the trace file as comment:
- .. code-block:: shell
+ .. code-block:: none
--cfg=tracing/comment:my_simulation_identifier
- Add the contents of a textual file on top of the trace file as comment:
- .. code-block:: shell
+ .. code-block:: none
--cfg=tracing/comment-file:my_file_with_additional_information.txt
simulations. For additional details about this and all tracing
options, check See the :ref:`tracing_tracing_options`.
-Configuring MSG
----------------
-
-.. _cfg=msg/debug-multiple-use:
-
-Debugging MSG Code
-..................
-
-**Option** ``msg/debug-multiple-use`` **Default:** off
-
-Sometimes your application may try to send a task that is still being
-executed somewhere else, making it impossible to send this task. However,
-for debugging purposes, one may want to know what the other host is/was
-doing. This option shows a backtrace of the other process.
-
Configuring SMPI
----------------
The SMPI interface provides several specific configuration items.
-These are not easy to see, since the code is usually launched through the
-``smiprun`` script directly.
+These are not easy to see with ``--help-cfg``, since SMPI binaries are usually launched through the ``smiprun`` script.
.. _cfg=smpi/host-speed:
.. _cfg=smpi/cpu-threshold:
first column defines the section that will be subject to a speedup;
the second column is the speedup. For instance:
-.. code-block:: shell
+.. code-block:: none
"start:stop","ratio"
"exchange_1.f:30:exchange_1.f:130",1.18244559422142
smpicc or smpiff, respectively. This flag activates some internal
macro definitions that help with obtaining the call location.
-.. _cfg=smpi/bw-factor:
-
-Bandwidth Factors
-.................
-
-**Option** ``smpi/bw-factor``
-|br| **Default:** 65472:0.940694;15424:0.697866;9376:0.58729;5776:1.08739;3484:0.77493;1426:0.608902;732:0.341987;257:0.338112;0:0.812084
-
-The possible throughput of network links is often dependent on the
-message sizes, as protocols may adapt to different message sizes. With
-this option, a series of message sizes and factors are given, helping
-the simulation to be more realistic. For instance, the current default
-value means that messages with size 65472 bytes and more will get a total of
-MAX_BANDWIDTH*0.940694, messages of size 15424 to 65471 will get
-MAX_BANDWIDTH*0.697866, and so on (where MAX_BANDWIDTH denotes the
-bandwidth of the link).
+Bandwidth and latency factors
+.............................
-An experimental script to compute these factors is available online. See
-https://framagit.org/simgrid/platform-calibration/
-https://simgrid.org/contrib/smpi-saturation-doc.html
+Adapting the bandwidth and latency acurately to the network conditions is of a paramount importance to get realistic results.
+This is done through the :ref:`network/bandwidth-factor <cfg=network/bandwidth-factor>` and :ref:`network/latency-factor
+<cfg=network/latency-factor>` items. You probably also want to read the following section: :ref:`models_calibration`.
.. _cfg=smpi/display-timing:
under the dlopen privatization schema, which tends to fool the
debuggers.
-.. _cfg=smpi/lat-factor:
-
-Latency factors
-...............
-
-**Option** ``smpi/lat-factor`` |br|
-**default:** 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
-
-The motivation and syntax for this option is identical to the motivation/syntax
-of :ref:`cfg=smpi/bw-factor`.
-
-There is an important difference, though: While smpi/bw-factor `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.
-
.. _cfg=smpi/papi-events:
Trace hardware counters with PAPI
The first draft, however, just implements a "global" (i.e., for all processes) set
of counters, the "default" set.
-.. code-block:: shell
+.. code-block:: none
--cfg=smpi/papi-events:"default:PAPI_L3_LDM:PAPI_L2_LDM"
or full names. Check with ldd the name of the library you want to
use. For example:
-.. code-block:: shell
+.. code-block:: console
- ldd allpairf90
+ $ ldd allpairf90
...
libgfortran.so.3 => /usr/lib/x86_64-linux-gnu/libgfortran.so.3 (0x00007fbb4d91b000)
...
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`.
+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:
+
+Add a barrier in all collectives
+................................
+
+**Option** ``smpi/barrier-collectives`` **default:** off
+
+This option adds a simple barrier in some collective operations to catch dangerous
+code that may or may not work depending on the MPI implementation: Bcast, Exscan,
+Gather, Gatherv, Scan, Scatter, Scatterv and Reduce.
+
+For example, the following code works with OpenMPI while it deadlocks in MPICH and
+Intel MPI. Broadcast seem to be "fire and forget" in OpenMPI while other
+implementations expect to receive a message.
-.. TODO:: All available collective algorithms will be made available
- via the ``smpirun --help-coll`` command.
+.. code-block:: C
+
+ if (rank == 0) {
+ MPI_Bcast(buf1, buff_size, MPI_CHAR, 0, newcom);
+ MPI_Send(&buf2, buff_size, MPI_CHAR, 1, tag, newcom);
+ } else if (rank==1) {
+ MPI_Recv(&buf2, buff_size, MPI_CHAR, 0, tag, newcom, MPI_STATUS_IGNORE);
+ MPI_Bcast(buf1, buff_size, MPI_CHAR, 0, newcom);
+ }
+
+The barrier is only simulated and does not involve any additional message (it is a S4U barrier).
+This option is disabled by default, and activated by the `-analyze` flag of smpirun.
+
+.. _cfg=smpi/barrier-finalization:
Add a barrier in MPI_Finalize
.............................
-.. _cfg=smpi/finalization-barrier:
-
**Option** ``smpi/finalization-barrier`` **default:** off
By default, SMPI processes are destroyed as soon as soon as their code ends,
.. _cfg=smpi/errors-are-fatal:
+Disable MPI fatal errors
+........................
+
**Option** ``smpi/errors-are-fatal`` **default:** on
By default, SMPI processes will crash if a MPI error code is returned. MPI allows
will turn on this behaviour by default (for all concerned types and errhandlers).
This can ease debugging by going after the first reported error.
+.. _cfg=smpi/pedantic:
+
+Disable pedantic MPI errors
+...........................
+
+**Option** ``smpi/pedantic`` **default:** on
+
+By default, SMPI will report all errors it finds in MPI codes. Some of these errors
+may not be considered as errors by all developers. This flag can be turned off to
+avoid reporting some usually harmless mistakes.
+Concerned errors list (will be expanded in the future):
+
+ - Calling MPI_Win_fence only once in a program, hence just opening an epoch without
+ ever closing it.
+
.. _cfg=smpi/iprobe:
Inject constant times for MPI_Iprobe
assignment). In practice, change the calls for malloc() and free() into
SMPI_SHARED_MALLOC() and SMPI_SHARED_FREE().
-SMPI provides two algorithms for this feature. The first one, called
+SMPI provides two algorithms for this feature. The first one, called
``local``, allocates one block per call to SMPI_SHARED_MALLOC()
(each call site gets its own block) ,and this block is shared
among all MPI ranks. This is implemented with the shm_* functions
To activate this, you must mount a hugetlbfs on your system and allocate
at least one huge page:
-.. code-block:: shell
+.. code-block:: console
- mkdir /home/huge
- sudo mount none /home/huge -t hugetlbfs -o rw,mode=0777
- sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages' # echo more if you need more
+ $ mkdir /home/huge
+ $ sudo mount none /home/huge -t hugetlbfs -o rw,mode=0777
+ $ sudo sh -c 'echo 1 > /proc/sys/vm/nr_hugepages' # echo more if you need more
Then, you can pass the option
``--cfg=smpi/shared-malloc-hugepage:/home/huge`` to smpirun to
the execution and get a backtrace with a debugger.
It is also possible to set the breakpoint from inside the debugger, by
-writing in global variable simgrid::simix::breakpoint. For example,
+writing in global variable simgrid::kernel::cfg_breakpoint. For example,
with gdb:
-.. code-block:: shell
+.. code-block:: none
- set variable simgrid::simix::breakpoint = 3.1416
+ set variable simgrid::kernel::cfg_breakpoint = 3.1416
.. _cfg=debug/verbose-exit:
If you want to have spaces in your log format, you should protect it. Otherwise, SimGrid will consider that this is a space-separated list of several parameters. But you should
-also protect it from the shell that also splits command line arguments on spaces. At the end, you should use something such as ``--log="'root.fmt:%l: [%p/%c]: %m%n'"``.
-Another option is to use the ``%e`` directive for spaces, as in ``--log=root.fmt:%l:%e[%p/%c]:%e%m%n``.
+also protect it from the shell that also splits command line arguments on spaces. At the end, you should use something such as ``--log="'root.fmt:%l: [%p/%c]: %m%n'"``.
+Another option is to use the ``%e`` directive for spaces, as in ``--log=root.fmt:%l:%e[%p/%c]:%e%m%n``.
Category appender
.................
