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 :cpp:func:`simgrid::s4u::Comm::wait_all()` function is useful
 167    when you want to block until all activities in a given set have
 168    completed.
 169    |br| `examples/s4u/async-waitall/s4u-async-waitall.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/async-waitall/s4u-async-waitall.cpp>`_
 170
 171  - **Waiting for the first completed communication in a set:**
 172    The :cpp:func:`simgrid::s4u::Comm::wait_any()` function is useful
 173    when you want to block until one activity of the set completes, no
 174    matter which terminates first.
 175    |br| `examples/s4u/async-waitany/s4u-async-waitany.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/async-waitany/s4u-async-waitany.cpp>`_
 176
 177 .. todo:: review the `ready` and `waituntil` examples and add them here.
 178
 179 .. _s4u_ex_execution:
 180
 181 Executions on the CPU
 182 ---------------------
 183
 184   - **Basic execution:**
 185     The computations done in your program are not reported to the
 186     simulated world, unless you explicitely request the simulator to pause
 187     the actor until a given amount of flops gets computed on its simulated
 188     host. Some executions can be given an higher priority so that they
 189     get more resources.
 190
 191     - |cpp| `examples/s4u/exec-basic/s4u-exec-basic.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-basic/s4u-exec-basic.cpp>`_
 192     - |py|  `examples/python/exec-basic/exec-basic.py <https://framagit.org/simgrid/simgrid/tree/master/examples/python/exec-basic/exec-basic.py>`_
 193
 194   - **Asynchronous execution:**
 195     You can start asynchronous executions, just like you would fire
 196     background threads.
 197     |br| `examples/s4u/exec-async/s4u-exec-async.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-async/s4u-exec-async.cpp>`_
 198
 199   - **Monitoring asynchronous executions:**
 200     This example shows how to start an asynchronous execution, and
 201     monitor its status.
 202     |br| `examples/s4u/exec-monitor/s4u-exec-monitor.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-monitor/s4u-exec-monitor.cpp>`_
 203
 204   - **Remote execution:**
 205     Before its start, you can change the host on which a given execution will occur.
 206     |br| `examples/s4u/exec-remote/s4u-exec-remote.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-remote/s4u-exec-remote.cpp>`_
 207
 208   - **Using Pstates on a host:**
 209     Shows how define a set of pstatesfor a host in the XML, and how the current
 210     pstate can be accessed/changed with :cpp:func:`simgrid::s4u::Host::get_pstate_speed` and :cpp:func:`simgrid::s4u::Host::set_pstate`.
 211     |br| `examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-dvfs/s4u-exec-dvfs.cpp>`_
 212     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 213
 214   - **Parallel executions:**
 215     These objects are convenient abstractions of parallel
 216     computational kernels that span over several machines, such as a
 217     PDGEM and the other ScaLAPACK routines.
 218     |br| `examples/s4u/exec-ptask/s4u-exec-ptask.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/exec-ptask/s4u-exec-ptask.cpp>`_
 219
 220 I/O on Disks and Files
 221 ----------------------
 222
 223 SimGrid provides two levels of abstraction to interact with the
 224 simulated storages. At the simplest level, you simply create read and
 225 write actions on the storage resources.
 226
 227   - **Access to raw storage devices:**
 228     This example illustrates how to simply read and write data on a
 229     simulated storage resource.
 230     |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>`_
 231
 232 The FileSystem plugin provides a more detailed view, with the
 233 classical operations over files: open, move, unlink, and of course
 234 read and write. The file and disk sizes are also dealt with and can
 235 result in short reads and short write, as in reality.
 236
 237   - **File Management:**
 238     This example illustrates the use of operations on files
 239     (read, write, seek, tell, unlink, etc).
 240     |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>`_
 241
 242   - **Remote I/O:**
 243     I/O operations on files can also be done in a remote fashion,
 244     i.e. when the accessed disk is not mounted on the caller's host.
 245     |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>`_
 246
 247 Classical synchronization objects
 248 ---------------------------------
 249
 250  - **Mutex:**
 251    Shows how to use simgrid::s4u::Mutex synchronization objects.
 252    |br| `examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-mutex/s4u-synchro-mutex.cpp>`_
 253
 254  - **Barrier:**
 255    Shows how to use simgrid::s4u::Barrier synchronization objects.
 256    |br| `examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-barrier/s4u-synchro-barrier.cpp>`_
 257
 258  - **Semaphore:**
 259    Shows how to use simgrid::s4u::Semaphore synchronization objects.
 260    |br| `examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/synchro-semaphore/s4u-synchro-semaphore.cpp>`_
 261
 262 =============================
 263 Interacting with the Platform
 264 =============================
 265
 266  - **Retrieving the list of hosts matching a given criteria:**
 267    Shows how to filter the actors that match a given criteria.
 268    |br| `examples/s4u/engine-filtering/s4u-engine-filtering.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/engine-filtering/s4u-engine-filtering.cpp>`_
 269
 270  - **User-defined properties:**
 271    You can attach arbitrary information to most platform elements from
 272    the XML file, and then interact with these values from your
 273    program. Note that the changes are not written permanently on disk,
 274    in the XML file nor anywhere else. They only last until the end of
 275    your simulation.
 276
 277    - :cpp:func:`simgrid::s4u::Actor::get_property()` and :cpp:func:`simgrid::s4u::Actor::set_property()`
 278    - :cpp:func:`simgrid::s4u::Host::get_property()` and :cpp:func:`simgrid::s4u::Host::set_property()`
 279    - :cpp:func:`simgrid::s4u::Link::get_property()` and :cpp:func:`simgrid::s4u::Link::set_property()`
 280    - :cpp:func:`simgrid::s4u::NetZone::get_property()` and :cpp:func:`simgrid::s4u::NetZone::set_property()`
 281
 282    |br| `examples/s4u/platform-properties/s4u-platform-properties.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/platform-properties/s4u-platform-properties.cpp>`_
 283    |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>`_
 284    |br| `examples/platforms/prop.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/prop.xml>`_
 285
 286  - **Specifying state profiles:** shows how to specify when the
 287    resources must be turned off and on again, and how to react to such
 288    failures in your code.
 289
 290    |br| `examples/platforms/small_platform_with_failure.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_with_failure.xml>`_
 291    |br| The state profiles in `examples/platforms/profiles <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 292
 293  - **Specifying speed profiles:** shows how to specify an external
 294    load to resources, variating their peak speed over time.
 295
 296    |br| `examples/platforms/small_platform_profile.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/small_platform_profile.xml>`_
 297    |br| The speed, bandwidth and latency profiles in `examples/platforms/profiles  <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/profiles>`_
 298
 299 =================
 300 Energy Simulation
 301 =================
 302
 303   - **Describing the energy profiles in the platform:**
 304     This platform file contains the energy profile of each links and
 305     hosts, which is necessary to get energy consumption predictions.
 306     As usual, you should not trust our example, and you should strive
 307     to double-check that your instanciation matches your target platform.
 308     |br| `examples/platforms/energy_platform.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/platforms/energy_platform.xml>`_
 309
 310   - **Consumption due to the CPU:**
 311     This example shows how to retrieve the amount of energy consumed
 312     by the CPU during computations, and the impact of the pstate.
 313     |br| `examples/s4u/energy-exec/s4u-energy-exec.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-exec/s4u-energy-exec.cpp>`_
 314
 315   - **Consumption due to the network:**
 316     This example shows how to retrieve and display the energy consumed
 317     by the network during communications.
 318     |br| `examples/s4u/energy-link/s4u-energy-link.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-link/s4u-energy-link.cpp>`_
 319
 320   - **Modeling the shutdown and boot of hosts:**
 321     Simple example of model of model for the energy consumption during
 322     the host boot and shutdown periods.
 323     |br| `examples/s4u/energy-boot/platform_boot.xml <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/platform_boot.xml>`_
 324     |br| `examples/s4u/energy-boot/s4u-energy-boot.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/energy-boot/s4u-energy-boot.cpp>`_
 325
 326 =======================
 327 Tracing and Visualizing
 328 =======================
 329
 330 Tracing can be activated by various configuration options which
 331 are illustrated in these example. See also the
 332 :ref:`full list of options related to tracing <tracing_tracing_options>`.
 333
 334 It is interesting to run the process-create example with the following
 335 options to see the task executions:
 336
 337   - **Platform Tracing:**
 338     This program is a toy example just loading the platform, so that
 339     you can play with the platform visualization. Recommanded options:
 340     ``--cfg=tracing:yes --cfg=tracing/categorized:yes``
 341     |br| `examples/s4u/trace-platform/s4u-trace-platform.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/trace-platform/s4u-trace-platform.cpp>`_
 342
 343 ========================
 344 Larger SimGrid Examplars
 345 ========================
 346
 347 This section contains application examples that are somewhat larger
 348 than the previous examples.
 349
 350   - **Ping Pong:**
 351     This simple example just sends one message back and forth.
 352     The tesh file laying in the directory show how to start the simulator binary, highlighting how to pass options to
 353     the simulators (as detailed in Section :ref:`options`).
 354     |br| `examples/s4u/app-pingpong/s4u-app-pingpong.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-pingpong/s4u-app-pingpong.cpp>`_
 355
 356   - **Token ring:**
 357     Shows how to implement a classical communication pattern, where a
 358     token is exchanged along a ring to reach every participant.
 359     |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>`_
 360
 361   - **Master Workers:**
 362     Another good old example, where one Master process has a bunch of task to dispatch to a set of several Worker
 363     processes. This example comes in two equivalent variants, one
 364     where the actors are specified as simple functions (which is easier to
 365     understand for newcomers) and one where the actors are specified
 366     as classes (which is more powerful for the users wanting to build
 367     their own projects upon the example).
 368     |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>`_
 369     |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>`_
 370
 371 Data diffusion
 372 --------------
 373
 374   - **Bit Torrent:**
 375     Classical protocol for Peer-to-Peer data diffusion.
 376     |br| `examples/s4u/app-bittorrent/s4u-bittorrent.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-bittorrent/s4u-bittorrent.cpp>`_
 377
 378   - **Chained Send:**
 379     Data broadcast over a ring of processes.
 380     |br| `examples/s4u/app-chainsend/s4u-app-chainsend.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/app-chainsend/s4u-app-chainsend.cpp>`_
 381
 382 Distributed Hash Tables (DHT)
 383 -----------------------------
 384
 385   - **Chord Protocol**
 386     One of the most famous DHT protocol.
 387     |br| `examples/s4u/dht-chord/s4u-dht-chord.cpp <https://framagit.org/simgrid/simgrid/tree/master/examples/s4u/dht-chord/s4u-dht-chord.cpp>`_
 388
 389 .. TODO:: document here the examples about plugins
 390
 391 .. |br| raw:: html
 392
 393    <br />
 394
 395 .. |cpp| image:: /img/lang_cpp.png
 396    :align: middle
 397    :width: 12
 398
 399 .. |py| image:: /img/lang_python.png
 400    :align: middle
 401    :width: 12