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   - **Monitoring asynchronous executions:**
 207     This example shows how to start an asynchronous execution, and
 208     monitor its status.
 209     |br| `examples/s4u/exec-monitor/s4u-exec-monitor.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-monitor/s4u-exec-monitor.cpp>`_
 210
 211   - **Remote execution:**
 212     Before its start, you can change the host on which a given execution will occur.
 213     |br| `examples/s4u/exec-remote/s4u-exec-remote.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-remote/s4u-exec-remote.cpp>`_
 214
 215   - **Using Pstates on a host:**
 216     Shows how define a set of pstatesfor a host in the XML, and how the current
 217     pstate can be accessed/changed with :cpp:func:`simgrid::s4u::Host::get_pstate_speed` and :cpp:func:`simgrid::s4u::Host::set_pstate`.
 218     |br| `examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp>`_
 219     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 220
 221   - **Parallel executions:**
 222     These objects are convenient abstractions of parallel
 223     computational kernels that span over several machines, such as a
 224     PDGEM and the other ScaLAPACK routines.
 225     |br| `examples/s4u/exec-ptask/s4u-exec-ptask.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-ptask/s4u-exec-ptask.cpp>`_
 226
 227 I/O on Disks and Files
 228 ----------------------
 229
 230 SimGrid provides two levels of abstraction to interact with the
 231 simulated storages. At the simplest level, you simply create read and
 232 write actions on the storage resources.
 233
 234   - **Access to raw storage devices:**
 235     This example illustrates how to simply read and write data on a
 236     simulated storage resource.
 237     |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>`_
 238
 239 The FileSystem plugin provides a more detailed view, with the
 240 classical operations over files: open, move, unlink, and of course
 241 read and write. The file and disk sizes are also dealt with and can
 242 result in short reads and short write, as in reality.
 243
 244   - **File Management:**
 245     This example illustrates the use of operations on files
 246     (read, write, seek, tell, unlink, etc).
 247     |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>`_
 248
 249   - **Remote I/O:**
 250     I/O operations on files can also be done in a remote fashion,
 251     i.e. when the accessed disk is not mounted on the caller's host.
 252     |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>`_
 253
 254 Classical synchronization objects
 255 ---------------------------------
 256
 257  - **Mutex:**
 258    Shows how to use simgrid::s4u::Mutex synchronization objects.
 259    |br| `examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp>`_
 260
 261  - **Barrier:**
 262    Shows how to use simgrid::s4u::Barrier synchronization objects.
 263    |br| `examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp>`_
 264
 265  - **Semaphore:**
 266    Shows how to use simgrid::s4u::Semaphore synchronization objects.
 267    |br| `examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp>`_
 268
 269 =============================
 270 Interacting with the Platform
 271 =============================
 272
 273  - **Retrieving the list of hosts matching a given criteria:**
 274    Shows how to filter the actors that match a given criteria.
 275    |br| `examples/s4u/engine-filtering/s4u-engine-filtering.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/engine-filtering/s4u-engine-filtering.cpp>`_
 276
 277  - **User-defined properties:**
 278    You can attach arbitrary information to most platform elements from
 279    the XML file, and then interact with these values from your
 280    program. Note that the changes are not written permanently on disk,
 281    in the XML file nor anywhere else. They only last until the end of
 282    your simulation.
 283
 284    - :cpp:func:`simgrid::s4u::Actor::get_property()` and :cpp:func:`simgrid::s4u::Actor::set_property()`
 285    - :cpp:func:`simgrid::s4u::Host::get_property()` and :cpp:func:`simgrid::s4u::Host::set_property()`
 286    - :cpp:func:`simgrid::s4u::Link::get_property()` and :cpp:func:`simgrid::s4u::Link::set_property()`
 287    - :cpp:func:`simgrid::s4u::NetZone::get_property()` and :cpp:func:`simgrid::s4u::NetZone::set_property()`
 288
 289    |br| `examples/s4u/platform-properties/s4u-platform-properties.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/platform-properties/s4u-platform-properties.cpp>`_
 290    |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>`_
 291    |br| `examples/platforms/prop.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/prop.xml>`_
 292
 293  - **Specifying state profiles:** shows how to specify when the
 294    resources must be turned off and on again, and how to react to such
 295    failures in your code.
 296
 297    |br| `examples/platforms/small_platform_with_failure.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_with_failure.xml>`_
 298    |br| The state profiles in `examples/platforms/profiles <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 299
 300  - **Specifying speed profiles:** shows how to specify an external
 301    load to resources, variating their peak speed over time.
 302
 303    |br| `examples/platforms/small_platform_profile.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_profile.xml>`_
 304    |br| The speed, bandwidth and latency profiles in `examples/platforms/profiles  <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 305
 306 =================
 307 Energy Simulation
 308 =================
 309
 310   - **Describing the energy profiles in the platform:**
 311     This platform file contains the energy profile of each links and
 312     hosts, which is necessary to get energy consumption predictions.
 313     As usual, you should not trust our example, and you should strive
 314     to double-check that your instanciation matches your target platform.
 315     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 316
 317   - **Consumption due to the CPU:**
 318     This example shows how to retrieve the amount of energy consumed
 319     by the CPU during computations, and the impact of the pstate.
 320     |br| `examples/s4u/energy-exec/s4u-energy-exec.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-exec/s4u-energy-exec.cpp>`_
 321
 322   - **Consumption due to the network:**
 323     This example shows how to retrieve and display the energy consumed
 324     by the network during communications.
 325     |br| `examples/s4u/energy-link/s4u-energy-link.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-link/s4u-energy-link.cpp>`_
 326
 327   - **Modeling the shutdown and boot of hosts:**
 328     Simple example of model of model for the energy consumption during
 329     the host boot and shutdown periods.
 330     |br| `examples/s4u/energy-boot/platform_boot.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/platform_boot.xml>`_
 331     |br| `examples/s4u/energy-boot/s4u-energy-boot.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/s4u-energy-boot.cpp>`_
 332
 333 =======================
 334 Tracing and Visualizing
 335 =======================
 336
 337 Tracing can be activated by various configuration options which
 338 are illustrated in these example. See also the
 339 :ref:`full list of options related to tracing <tracing_tracing_options>`.
 340
 341 It is interesting to run the process-create example with the following
 342 options to see the task executions:
 343
 344   - **Platform Tracing:**
 345     This program is a toy example just loading the platform, so that
 346     you can play with the platform visualization. Recommanded options:
 347     ``--cfg=tracing:yes --cfg=tracing/categorized:yes``
 348     |br| `examples/s4u/trace-platform/s4u-trace-platform.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/trace-platform/s4u-trace-platform.cpp>`_
 349
 350 ========================
 351 Larger SimGrid Examplars
 352 ========================
 353
 354 This section contains application examples that are somewhat larger
 355 than the previous examples.
 356
 357   - **Ping Pong:**
 358     This simple example just sends one message back and forth.
 359     The tesh file laying in the directory show how to start the simulator binary, highlighting how to pass options to
 360     the simulators (as detailed in Section :ref:`options`).
 361     |br| `examples/s4u/app-pingpong/s4u-app-pingpong.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-pingpong/s4u-app-pingpong.cpp>`_
 362
 363   - **Token ring:**
 364     Shows how to implement a classical communication pattern, where a
 365     token is exchanged along a ring to reach every participant.
 366     |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>`_
 367
 368   - **Master Workers:**
 369     Another good old example, where one Master process has a bunch of task to dispatch to a set of several Worker
 370     processes. This example comes in two equivalent variants, one
 371     where the actors are specified as simple functions (which is easier to
 372     understand for newcomers) and one where the actors are specified
 373     as classes (which is more powerful for the users wanting to build
 374     their own projects upon the example).
 375     |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>`_
 376     |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>`_
 377
 378 Data diffusion
 379 --------------
 380
 381   - **Bit Torrent:**
 382     Classical protocol for Peer-to-Peer data diffusion.
 383     |br| `examples/s4u/app-bittorrent/s4u-bittorrent.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-bittorrent/s4u-bittorrent.cpp>`_
 384
 385   - **Chained Send:**
 386     Data broadcast over a ring of processes.
 387     |br| `examples/s4u/app-chainsend/s4u-app-chainsend.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-chainsend/s4u-app-chainsend.cpp>`_
 388
 389 Distributed Hash Tables (DHT)
 390 -----------------------------
 391
 392   - **Chord Protocol**
 393     One of the most famous DHT protocol.
 394     |br| `examples/s4u/dht-chord/s4u-dht-chord.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/dht-chord/s4u-dht-chord.cpp>`_
 395
 396 .. TODO:: document here the examples about plugins
 397
 398 .. |br| raw:: html
 399
 400    <br />
 401
 402 .. |cpp| image:: /img/lang_cpp.png
 403    :align: middle
 404    :width: 12
 405
 406 .. |py| image:: /img/lang_python.png
 407    :align: middle
 408    :width: 12