examples/s4u/README.rst

   1 .. S4U (Simgrid for you) is the next interface of SimGrid, expected to be released with SimGrid 4.0.
   2 ..
   3 .. Even if it is not completely rock stable yet, it may well already fit
   4 .. your needs. You are welcome to try it and report any interface
   5 .. glitches that you see. Be however warned that the interface may change
   6 .. until the final release.  You will have to adapt your code on the way.
   7 ..
   8 .. This file follows the ReStructured syntax to be included in the
   9 .. documentation, but it should remain readable directly.
  10
  11
  12 S4U Examples
  13 ************
  14
  15 SimGrid comes with an extensive set of examples, documented on this
  16 page. Most of them only demonstrate one single feature, with some
  17 larger examplars listed below.
  18
  19 The C++ examples can be found under examples/s4u while python examples
  20 are in examples/python. Each such directory contains the source code (also listed
  21 from this page), and the so-called tesh file containing how to call
  22 the binary obtained by compiling this example and also the expected
  23 output. Tesh files are used to turn each of our examples into an
  24 integration test. Some examples also contain other files, on need.
  25
  26 A good way to bootstrap your own project is to copy and combine some
  27 of the provided examples to constitute the skeleton of what you plan
  28 to simulate.
  29
  30 ===========================
  31 Actors: the Active Entities
  32 ===========================
  33
  34
  35 Starting and Stoping Actors
  36 ---------------------------
  37
  38   - **Creating actors:**
  39     Most actors are started from the deployment XML file, but there is other methods.
  40     This example show them all.
  41     `examples/python/actor-create/actor-create_d.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-create/actor-create_d.xml>`_
  42
  43     - |cpp| `examples/s4u/actor-create/s4u-actor-create.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-create/s4u-actor-create.cpp>`_
  44     - |py|  `examples/python/actor-create/actor-create.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-create/actor-create.py>`_
  45
  46   - **React to the end of actors:**
  47     You can attach a callback to the end of actors. There is two ways
  48     of doing so, depending of whether you want your callback to be
  49     executed when a specific actor ends (with ```this_actor::on_exit()```)
  50     or whether it should be executed when any actor ends (with
  51     ```Actor::on_destruction()```)
  52
  53     - |cpp| `examples/s4u/actor-exiting/s4u-actor-exiting.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-exiting/s4u-actor-exiting.cpp>`_
  54
  55   - **Kill actors:**
  56     Actors can forcefully stop other actors.
  57
  58     - |cpp| `examples/s4u/actor-kill/s4u-actor-kill.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-kill/s4u-actor-kill.cpp>`_
  59       :cpp:func:`void simgrid::s4u::Actor::kill(void)`,
  60       :cpp:func:`void simgrid::s4u::Actor::kill_all()`,
  61       :cpp:func:`simgrid::s4u::this_actor::exit`.
  62     - |py| `examples/python/actor-kill/actor-kill.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-kill/actor-kill.py>`_
  63       :py:func:`simgrid.Actor.kill`,
  64       :py:func:`simgrid.Actor.kill_all`,
  65       :py:func:`simgrid.this_actor.exit`.
  66
  67   - **Controling the actor life cycle from the XML:**
  68     You can specify a start time and a kill time in the deployment
  69     file.
  70     |br| `examples/s4u/actor-lifetime/s4u-actor-lifetime.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-lifetime/s4u-actor-lifetime.cpp>`_
  71     |br| `examples/s4u/actor-lifetime/s4u-actor-lifetime_d.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-lifetime/s4u-actor-lifetime_d.xml>`_
  72
  73   - **Daemonize actors:**
  74     Some actors may be intended to simulate daemons that run in background. This example show how to transform a regular
  75     actor into a daemon that will be automatically killed once the simulation is over.
  76
  77     - |cpp| `examples/s4u/actor-daemon/s4u-actor-daemon.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-daemon/s4u-actor-daemon.cpp>`_
  78     - |py|  `examples/python/actor-daemon/actor-daemon.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-daemon/actor-daemon.py>`_
  79
  80 Inter-Actors Interactions
  81 -------------------------
  82
  83   - **Suspend and Resume actors:**
  84     Actors can be suspended and resumed during their executions.
  85
  86     - |cpp| `examples/s4u/actor-suspend/s4u-actor-suspend.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-suspend/s4u-actor-suspend.cpp>`_
  87       :cpp:func:`simgrid::s4u::this_actor::suspend()`,
  88       :cpp:func:`simgrid::s4u::Actor::suspend()`, :cpp:func:`simgrid::s4u::Actor::resume()`, :cpp:func:`simgrid::s4u::Actor::is_suspended()`.
  89     - |py|  `examples/python/actor-suspend/actor-suspend.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-suspend/actor-suspend.py>`_
  90       :py:func:`simgrid.this_actor.suspend()`,
  91       :py:func:`simgrid.Actor.suspend()`, :py:func:`simgrid.Actor.resume()`, :py:func:`simgrid.Actor.is_suspended()`.
  92
  93   - **Migrating Actors:**
  94     Actors can move or be moved from a host to another very easily.
  95
  96     - |cpp| `examples/s4u/actor-migrate/s4u-actor-migrate.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-migrate/s4u-actor-migrate.cpp>`_
  97       :cpp:func:`simgrid::s4u::this_actor::migrate()`
  98     - |py|  `examples/python/actor-migrate/actor-migrate.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-migrate/actor-migrate.py>`_
  99       :py:func:`simgrid.this_actor.migrate()`
 100
 101   - **Waiting for the termination of an actor:** (joining on it)
 102     You can block the current actor until the end of another actor.
 103
 104     - |cpp| `examples/s4u/actor-join/s4u-actor-join.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-join/s4u-actor-join.cpp>`_
 105       :cpp:func:`simgrid::s4u::Actor::join()`
 106     - |py|  `examples/python/actor-join/actor-join.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-join/actor-join.py>`_
 107       :py:func:`simgrid.Actor.join()`
 108
 109   - **Yielding to other actors**.
 110     The ```yield()``` function interrupts the execution of the current
 111     actor, leaving a chance to the other actors that are ready to run
 112     at this timestamp.
 113
 114     - |cpp| `examples/s4u/actor-yield/s4u-actor-yield.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/actor-yield/s4u-actor-yield.cpp>`_
 115       :cpp:func:`simgrid::s4u::this_actor::yield()`
 116     - |py|  `examples/python/actor-yield/actor-yield.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/actor-yield/actor-yield.py>`_
 117       :py:func:`simgrid.this_actor.yield_()`
 118
 119 Traces Replay as a Workload
 120 ---------------------------
 121
 122 This section details how to run trace-driven simulations. It is very
 123 handy when you want to test an algorithm or protocol that only react
 124 to external events. For example, many P2P protocols react to user
 125 requests, but do nothing if there is no such event.
 126
 127 In such situations, you should write your protocol in C++, and separate
 128 the workload that you want to play onto your protocol in a separate
 129 text file. Declare a function handling each type of the events in your
 130 trace, register them using :cpp:func:`xbt_replay_action_register()` in
 131 your main, and then run the simulation.
 132
 133 Then, you can either have one trace file containing all your events,
 134 or a file per simulated process: the former may be easier to work
 135 with, but the second is more efficient on very large traces. Check
 136 also the tesh files in the example directories for details.
 137
 138   - **Communication replay:**
 139     Presents a set of event handlers reproducing classical communication
 140     primitives (asynchronous send/receive at the moment).
 141     |br| `examples/s4u/replay-comm/s4u-replay-comm.cpp  <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/replay-comm/s4u-replay-comm.cpp>`_
 142
 143   - **I/O replay:**
 144     Presents a set of event handlers reproducing classical I/O
 145     primitives (open, read, close).
 146     |br| `examples/s4u/replay-storage/s4u-replay-storage.cpp  <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/replay-storage/s4u-replay-storage.cpp>`_
 147
 148 ==========================
 149 Activities: what Actors do
 150 ==========================
 151
 152 Communications on the Network
 153 -----------------------------
 154
 155  - **Basic asynchronous communications:**
 156    Illustrates how to have non-blocking communications, that are
 157    communications running in the background leaving the process free
 158    to do something else during their completion.
 159
 160    - |cpp| `examples/s4u/async-wait/s4u-async-wait.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/async-wait/s4u-async-wait.cpp>`_
 161      :cpp:func:`simgrid::s4u::Mailbox::put_async()` and :cpp:func:`simgrid::s4u::Comm::wait()`
 162    - |py|  `examples/python/async-wait/async-wait.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/async-wait/async-wait.py>`_
 163      :py:func:`simgrid.Mailbox.put_async()` :py:func:`simgrid.Comm.wait()`
 164
 165  - **Waiting for all communications in a set:**
 166    The `wait_all()` function is useful when you want to block until
 167    all activities in a given set have completed.
 168
 169    - |cpp| `examples/s4u/async-waitall/s4u-async-waitall.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/async-waitall/s4u-async-waitall.cpp>`_
 170      :cpp:func:`simgrid::s4u::Comm::wait_all()`
 171    - |py| `examples/python/async-waitall/async-waitall.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/async-waitall/async-waitall.py>`_
 172      :py:func:`simgrid.Comm.wait_all()`
 173
 174  - **Waiting for the first completed communication in a set:**
 175    The `wait_any()` function is useful
 176    when you want to block until one activity of the set completes, no
 177    matter which terminates first.
 178
 179    - |cpp| `examples/s4u/async-waitany/s4u-async-waitany.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/async-waitany/s4u-async-waitany.cpp>`_
 180      :cpp:func:`simgrid::s4u::Comm::wait_any()`
 181    - |py| `examples/python/async-waitany/async-waitany.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/async-waitany/async-waitany.py>`_
 182      :py:func:`simgrid.Comm.wait_any()`
 183
 184 .. todo:: review the `ready` and `waituntil` examples and add them here.
 185
 186 .. _s4u_ex_execution:
 187
 188 Executions on the CPU
 189 ---------------------
 190
 191   - **Basic execution:**
 192     The computations done in your program are not reported to the
 193     simulated world, unless you explicitely request the simulator to pause
 194     the actor until a given amount of flops gets computed on its simulated
 195     host. Some executions can be given an higher priority so that they
 196     get more resources.
 197
 198     - |cpp| `examples/s4u/exec-basic/s4u-exec-basic.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-basic/s4u-exec-basic.cpp>`_
 199     - |py|  `examples/python/exec-basic/exec-basic.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/exec-basic/exec-basic.py>`_
 200
 201   - **Asynchronous execution:**
 202     You can start asynchronous executions, just like you would fire
 203     background threads.
 204     |br| `examples/s4u/exec-async/s4u-exec-async.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-async/s4u-exec-async.cpp>`_
 205
 206   - **Remote execution:**
 207     You can start executions on remote hosts, or even change the host
 208     on which they occur during their execution.
 209     |br| `examples/s4u/exec-remote/s4u-exec-remote.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-remote/s4u-exec-remote.cpp>`_
 210
 211   - **Parallel executions:**
 212     These objects are convenient abstractions of parallel
 213     computational kernels that span over several machines, such as a
 214     PDGEM and the other ScaLAPACK routines. Note that this only works
 215     with the "ptask_L07" host model (`--cfg=host/model:ptask_L07`).
 216     |br| `examples/s4u/exec-ptask/s4u-exec-ptask.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-ptask/s4u-exec-ptask.cpp>`_
 217
 218   - **Using Pstates on a host:**
 219     Shows how define a set of pstatesfor a host in the XML, and how the current
 220     pstate can be accessed/changed with :cpp:func:`simgrid::s4u::Host::get_pstate_speed` and :cpp:func:`simgrid::s4u::Host::set_pstate`.
 221     |br| `examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp>`_
 222     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 223
 224 I/O on Disks and Files
 225 ----------------------
 226
 227 SimGrid provides two levels of abstraction to interact with the
 228 simulated storages. At the simplest level, you simply create read and
 229 write actions on the storage resources.
 230
 231   - **Access to raw storage devices:**
 232     This example illustrates how to simply read and write data on a
 233     simulated storage resource.
 234     |br| `examples/s4u/io-storage-raw/s4u-io-storage-raw.cpp  <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/io-storage-raw/s4u-io-storage-raw.cpp>`_
 235
 236 The FileSystem plugin provides a more detailed view, with the
 237 classical operations over files: open, move, unlink, and of course
 238 read and write. The file and disk sizes are also dealt with and can
 239 result in short reads and short write, as in reality.
 240
 241   - **File Management:**
 242     This example illustrates the use of operations on files
 243     (read, write, seek, tell, unlink, etc).
 244     |br| `examples/s4u/io-file-system/s4u-io-file-system.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/io-file-system/s4u-io-file-system.cpp>`_
 245
 246   - **Remote I/O:**
 247     I/O operations on files can also be done in a remote fashion,
 248     i.e. when the accessed disk is not mounted on the caller's host.
 249     |br| `examples/s4u/io-file-remote/s4u-io-file-remote.cpp  <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/io-file-remote/s4u-io-file-remote.cpp>`_
 250
 251 Classical synchronization objects
 252 ---------------------------------
 253
 254  - **Mutex:**
 255    Shows how to use simgrid::s4u::Mutex synchronization objects.
 256    |br| `examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp>`_
 257
 258  - **Barrier:**
 259    Shows how to use simgrid::s4u::Barrier synchronization objects.
 260    |br| `examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp>`_
 261
 262  - **Semaphore:**
 263    Shows how to use simgrid::s4u::Semaphore synchronization objects.
 264    |br| `examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp>`_
 265
 266 =============================
 267 Interacting with the Platform
 268 =============================
 269
 270  - **Retrieving the list of hosts matching a given criteria:**
 271    Shows how to filter the actors that match a given criteria.
 272    |br| `examples/s4u/engine-filtering/s4u-engine-filtering.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/engine-filtering/s4u-engine-filtering.cpp>`_
 273
 274  - **User-defined properties:**
 275    You can attach arbitrary information to most platform elements from
 276    the XML file, and then interact with these values from your
 277    program. Note that the changes are not written permanently on disk,
 278    in the XML file nor anywhere else. They only last until the end of
 279    your simulation.
 280
 281    - :cpp:func:`simgrid::s4u::Actor::get_property()` and :cpp:func:`simgrid::s4u::Actor::set_property()`
 282    - :cpp:func:`simgrid::s4u::Host::get_property()` and :cpp:func:`simgrid::s4u::Host::set_property()`
 283    - :cpp:func:`simgrid::s4u::Link::get_property()` and :cpp:func:`simgrid::s4u::Link::set_property()`
 284    - :cpp:func:`simgrid::s4u::NetZone::get_property()` and :cpp:func:`simgrid::s4u::NetZone::set_property()`
 285
 286    |br| `examples/s4u/platform-properties/s4u-platform-properties.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/platform-properties/s4u-platform-properties.cpp>`_
 287    |br| `examples/s4u/platform-properties/s4u-platform-properties_d.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/platform-properties/s4u-platform-properties_d.xml>`_
 288    |br| `examples/platforms/prop.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/prop.xml>`_
 289
 290  - **Specifying state profiles:** shows how to specify when the
 291    resources must be turned off and on again, and how to react to such
 292    failures in your code.
 293
 294    |br| `examples/platforms/small_platform_with_failure.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_with_failure.xml>`_
 295    |br| The state profiles in `examples/platforms/profiles <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 296
 297  - **Specifying speed profiles:** shows how to specify an external
 298    load to resources, variating their peak speed over time.
 299
 300    |br| `examples/platforms/small_platform_profile.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_profile.xml>`_
 301    |br| The speed, bandwidth and latency profiles in `examples/platforms/profiles  <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 302
 303 =================
 304 Energy Simulation
 305 =================
 306
 307   - **Describing the energy profiles in the platform:**
 308     This platform file contains the energy profile of each links and
 309     hosts, which is necessary to get energy consumption predictions.
 310     As usual, you should not trust our example, and you should strive
 311     to double-check that your instanciation matches your target platform.
 312     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 313
 314   - **Consumption due to the CPU:**
 315     This example shows how to retrieve the amount of energy consumed
 316     by the CPU during computations, and the impact of the pstate.
 317     |br| `examples/s4u/energy-exec/s4u-energy-exec.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-exec/s4u-energy-exec.cpp>`_
 318
 319   - **Consumption due to the network:**
 320     This example shows how to retrieve and display the energy consumed
 321     by the network during communications.
 322     |br| `examples/s4u/energy-link/s4u-energy-link.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-link/s4u-energy-link.cpp>`_
 323
 324   - **Modeling the shutdown and boot of hosts:**
 325     Simple example of model of model for the energy consumption during
 326     the host boot and shutdown periods.
 327     |br| `examples/s4u/energy-boot/platform_boot.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/platform_boot.xml>`_
 328     |br| `examples/s4u/energy-boot/s4u-energy-boot.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/s4u-energy-boot.cpp>`_
 329
 330 =======================
 331 Tracing and Visualizing
 332 =======================
 333
 334 Tracing can be activated by various configuration options which
 335 are illustrated in these example. See also the
 336 :ref:`full list of options related to tracing <tracing_tracing_options>`.
 337
 338 It is interesting to run the process-create example with the following
 339 options to see the task executions:
 340
 341   - **Platform Tracing:**
 342     This program is a toy example just loading the platform, so that
 343     you can play with the platform visualization. Recommanded options:
 344     ``--cfg=tracing:yes --cfg=tracing/categorized:yes``
 345     |br| `examples/s4u/trace-platform/s4u-trace-platform.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/trace-platform/s4u-trace-platform.cpp>`_
 346
 347 ========================
 348 Larger SimGrid Examplars
 349 ========================
 350
 351 This section contains application examples that are somewhat larger
 352 than the previous examples.
 353
 354   - **Ping Pong:**
 355     This simple example just sends one message back and forth.
 356     The tesh file laying in the directory show how to start the simulator binary, highlighting how to pass options to
 357     the simulators (as detailed in Section :ref:`options`).
 358     |br| `examples/s4u/app-pingpong/s4u-app-pingpong.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-pingpong/s4u-app-pingpong.cpp>`_
 359
 360   - **Token ring:**
 361     Shows how to implement a classical communication pattern, where a
 362     token is exchanged along a ring to reach every participant.
 363     |br| `examples/s4u/app-token-ring/s4u-app-token-ring.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-token-ring/s4u-app-token-ring.cpp>`_
 364
 365   - **Master Workers:**
 366     Another good old example, where one Master process has a bunch of task to dispatch to a set of several Worker
 367     processes. This example comes in two equivalent variants, one
 368     where the actors are specified as simple functions (which is easier to
 369     understand for newcomers) and one where the actors are specified
 370     as classes (which is more powerful for the users wanting to build
 371     their own projects upon the example).
 372     |br| `examples/s4u/app-masterworkers/s4u-app-masterworkers-class.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-masterworkers/s4u-app-masterworkers-class.cpp>`_
 373     |br| `examples/s4u/app-masterworkers/s4u-app-masterworkers-fun.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-masterworkers/s4u-app-masterworkers-fun.cpp>`_
 374
 375 Data diffusion
 376 --------------
 377
 378   - **Bit Torrent:**
 379     Classical protocol for Peer-to-Peer data diffusion.
 380     |br| `examples/s4u/app-bittorrent/s4u-bittorrent.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-bittorrent/s4u-bittorrent.cpp>`_
 381
 382   - **Chained Send:**
 383     Data broadcast over a ring of processes.
 384     |br| `examples/s4u/app-chainsend/s4u-app-chainsend.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-chainsend/s4u-app-chainsend.cpp>`_
 385
 386 Distributed Hash Tables (DHT)
 387 -----------------------------
 388
 389   - **Chord Protocol**
 390     One of the most famous DHT protocol.
 391     |br| `examples/s4u/dht-chord/s4u-dht-chord.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/dht-chord/s4u-dht-chord.cpp>`_
 392
 393 .. TODO:: document here the examples about plugins
 394
 395 .. |br| raw:: html
 396
 397    <br />
 398
 399 .. |cpp| image:: /img/lang_cpp.png
 400    :align: middle
 401    :width: 12
 402
 403 .. |py| image:: /img/lang_python.png
 404    :align: middle
 405    :width: 12