</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
- **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/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`
<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.
-
- - **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/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:: console
$ 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:
**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.
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)
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:
+and computational speed).
-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/strategy:
-.. _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:
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:: console
``--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
.............................
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/>`_.
you never used the tracing API.
-- Any SimGrid-based simulator (MSG, SMPI, ...) and raw traces:
+- Any SimGrid-based simulator (S4U, SMPI, ...) and raw traces:
.. code-block:: none
tells it to trace host and link utilization (without any
categorization).
-- MSG-based simulator and categorized traces (you need to
+- S4U-based simulator and categorized traces (you need to
declare categories and classify your tasks according to them)
.. code-block:: none
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.
+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:
