+.. _S4U_doc:
+
The S4U Interface
-=================
+#################
+
+.. raw:: html
+
+ <object id="TOC" data="graphical-toc.svg" width="100%" type="image/svg+xml"></object>
+ <script>
+ window.onload=function() { // Wait for the SVG to be loaded before changing it
+ var elem=document.querySelector("#TOC").contentDocument.getElementById("S4UBox")
+ elem.style="opacity:0.93999999;fill:#ff0000;fill-opacity:0.1";
+ }
+ </script>
+ <br/>
+ <br/>
+
+The S4U interface (SimGrid for you) mixes the full power of SimGrid
+with the full power of C++. This is the preferred interface to describe
+abstract algorithms in the domains of Cloud, P2P, HPC, IoT, and similar
+settings.
+
+Currently (v3.21), S4U is definitely the way to go for long-term
+projects. It is feature complete, but may still evolve slightly in the
+future releases. It can already be used to do everything that can be
+done in SimGrid, but you may have to adapt your code in future
+releases. When this happens, compiling your code will produce
+deprecation warnings for 4 releases (one year) before the removal of
+the old symbols.
+If you want an API that will never ever evolve in the future, you
+should use the deprecated MSG API instead.
+
+Main Concepts
+*************
+
+A typical SimGrid simulation is composed of several |API_s4u_Actors|_, that
+execute user-provided functions. The actors have to explicitly use the
+S4U interface to express their :ref:`computation <API_s4u_Exec>`,
+:ref:`communication <API_s4u_Comm>`, :ref:`disk usage <API_s4u_Io>`,
+and other |API_s4u_Activities|_, so that they get reflected within the
+simulator. These activities take place on resources such as |API_s4u_Hosts|_,
+|API_s4u_Links|_ and |API_s4u_Storages|_. SimGrid predicts the time taken by each
+activity and orchestrates the actors accordingly, waiting for the
+completion of these activities.
+
+
+When **communicating**, data is not directly sent to other actors but
+posted onto a |API_s4u_Mailbox|_ that serves as a rendez-vous point between
+communicating actors. This means that you don't need to know who you
+are talking to, you just put your communication `Put` request in a
+mailbox, and it will be matched with a complementary `Get`
+request. Alternatively, actors can interact through **classical
+synchronization mechanisms** such as |API_s4u_Barrier|_, |API_s4u_Semaphore|_,
+|API_s4u_Mutex|_ and |API_s4u_ConditionVariable|_.
+
+Each actor is located on a simulated |API_s4u_Host|_. Each host is located
+itself in a |API_s4u_NetZone|_, that knows the networking path between one
+resource to another. Each NetZone is included in another one, forming
+a tree of NetZones which root zone contains the whole platform.
+
+The :ref:`simgrid::s4u::this_actor <API_s4u_this_actor>` namespace
+provides many helper functions to simplify the code of actors.
+
+- **Global Classes**
+
+ - :ref:`class s4u::Actor <API_s4u_Actor>`:
+ Active entities executing your application.
+ - :ref:`class s4u::Engine <API_s4u_Engine>`
+ Simulation engine (singleton).
+ - :ref:`class s4u::Mailbox <API_s4u_Mailbox>`
+ Communication rendez-vous.
+
+- **Platform Elements**
+
+ - :ref:`class s4u::Host <API_s4u_Host>`:
+ Actor location, providing computational power.
+ - :ref:`class s4u::Link <API_s4u_Link>`
+ Interconnecting hosts.
+ - :ref:`class s4u::NetZone <API_s4u_NetZone>`:
+ Sub-region of the platform, containing resources (Hosts, Links, etc).
+ - :ref:`class s4u::Storage <API_s4u_Storage>`
+ Resource on which actors can write and read data.
+ - :ref:`class s4u::VirtualMachine <API_s4u_VirtualMachine>`:
+ Execution containers that can be moved between Hosts.
+
+- **Activities** (:ref:`class s4u::Activity <API_s4u_Activity>`):
+ The things that actors can do on resources
+
+ - :ref:`class s4u::Comm <API_s4u_Comm>`
+ Communication activity, started on Mailboxes and consuming links.
+ - :ref:`class s4u::Exec <API_s4u_Exec>`
+ Computation activity, started on Host and consuming CPU resources.
+ - :ref:`class s4u::Io <API_s4u_Io>`
+ I/O activity, started on and consumming Storages.
+
+- **Synchronization Mechanisms**: Classical IPC that actors can use
+
+ - :ref:`class s4u::Barrier <API_s4u_Barrier>`
+ - :ref:`class s4u::ConditionVariable <API_s4u_ConditionVariable>`
+ - :ref:`class s4u::Mutex <API_s4u_Mutex>`
+ - :ref:`class s4u::Semaphore <API_s4u_Semaphore>`
+
+
+.. |API_s4u_Actors| replace:: **Actors**
+.. _API_s4u_Actors: #s4u-actor
+
+.. |API_s4u_Activities| replace:: **Activities**
+.. _API_s4u_Activities: #s4u-activity
+
+.. |API_s4u_Hosts| replace:: **Hosts**
+.. _API_s4u_Hosts: #s4u-host
+
+.. |API_s4u_Links| replace:: **Links**
+.. _API_s4u_Links: #s4u-link
+
+.. |API_s4u_Storages| replace:: **Storages**
+.. _API_s4u_Storages: #s4u-storage
+
+.. |API_s4u_VirtualMachines| replace:: **VirtualMachines**
+.. _API_s4u_VirtualMachines: #s4u-virtualmachine
+
+.. |API_s4u_Host| replace:: **Host**
+
+.. |API_s4u_Mailbox| replace:: **Mailbox**
+
+.. |API_s4u_NetZone| replace:: **NetZone**
+
+.. |API_s4u_Barrier| replace:: **Barrier**
+
+.. |API_s4u_Semaphore| replace:: **Semaphore**
+
+.. |API_s4u_ConditionVariable| replace:: **ConditionVariable**
+
+.. |API_s4u_Mutex| replace:: **Mutex**
+
+.. THE EXAMPLES
+
+.. include:: ../../examples/s4u/README.rst
+
+Activities
+**********
+
+Activities represent the actions that consume a resource, such as a
+:ref:`s4u::Comm <API_s4u_Comm>` that consumes the *transmiting power* of
+:ref:`s4u::Link <API_s4u_Link>` resources.
+
+=======================
+Asynchronous Activities
+=======================
+
+Every activity can be either **blocking** or **asynchronous**. For
+example, :cpp:func:`s4u::Mailbox::put() <simgrid::s4u::Mailbox::put>`
+and :cpp:func:`s4u::Mailbox::get() <simgrid::s4u::Mailbox::get>`
+create blocking communications: the actor is blocked until the
+completion of that communication. Asynchronous communications do not
+block the actor during their execution but progress on their own.
+
+Once your asynchronous activity is started, you can test for its
+completion using :cpp:func:`s4u::Activity::test() <simgrid::s4u::Activity::test>`.
+This function returns ``true`` if the activity completed already.
+You can also use :cpp:func:`s4u::Activity::wait() <simgrid::s4u::Activity::wait>`
+to block until the completion of the activity. To wait for at most a given amount of time,
+use :cpp:func:`s4u::Activity::wait_for() <simgrid::s4u::Activity::wait_for>`.
+Finally, to wait at most until a specified time limit, use
+:cpp:func:`s4u::Activity::wait_until() <simgrid::s4u::Activity::wait_until>`.
+
+.. todo::
+
+ wait_for and wait_until are currently not implemented for Exec and Io activities.
+
+Every kind of activities can be asynchronous:
+
+ - :ref:`s4u::CommPtr <API_s4u_Comm>` are created with
+ :cpp:func:`s4u::Mailbox::put_async() <simgrid::s4u::Mailbox::put_async>` and
+ :cpp:func:`s4u::Mailbox::get_async() <simgrid::s4u::Mailbox::get_async>`.
+ - :ref:`s4u::IoPtr <API_s4u_Io>` are created with
+ :cpp:func:`s4u::Storage::read_async() <simgrid::s4u::Storage::read_async>` and
+ :cpp:func:`s4u::Storage::write_async() <simgrid::s4u::Storage::write_async>`.
+ - :ref:`s4u::ExecPtr <API_s4u_Exec>` are created with
+ :cpp:func:`s4u::Host::exec_async() <simgrid::s4u::Host::exec_async>`.
+ - In the future, it will become possible to have asynchronous IPC
+ such as asynchronous mutex lock requests.
+
+The following example shows how to have several concurrent
+communications ongoing. First, you have to declare a vector in which
+we will store the ongoing communications. It is also useful to have a
+vector of mailboxes.
+
+.. literalinclude:: ../../examples/s4u/async-waitall/s4u-async-waitall.cpp
+ :language: c++
+ :start-after: init-begin
+ :end-before: init-end
+ :dedent: 4
+
+Then, you start all the communications that should occur concurrently with
+:cpp:func:`s4u::Mailbox::put_async() <simgrid::s4u::Mailbox::put_async>`.
+Finally, the actor waits for the completion of all of them at once
+with
+:cpp:func:`s4u::Comm::wait_all() <simgrid::s4u::Comm::wait_all>`.
+
+.. literalinclude:: ../../examples/s4u/async-waitall/s4u-async-waitall.cpp
+ :language: c++
+ :start-after: put-begin
+ :end-before: put-end
+ :dedent: 4
+
+
+=====================
+Activities Life cycle
+=====================
+
+Sometimes, you want to change the setting of an activity before it even starts.
+
+.. todo:: write this section
+
+Memory Management
+*****************
+
+For sake of simplicity, we use `RAII
+<https://en.wikipedia.org/wiki/Resource_Acquisition_Is_Initialization>`_
+everywhere in S4U. This is an idiom where resources are automatically
+managed through the context. Provided that you never manipulate
+objects of type Foo directly but always FooPtr references (which are
+defined as `boost::intrusive_ptr
+<http://www.boost.org/doc/libs/1_61_0/libs/smart_ptr/intrusive_ptr.html>`_
+<Foo>), you will never have to explicitely release the resource that
+you use nor to free the memory of unused objects.
+
+Here is a little example:
+
+.. code-block:: cpp
+
+ void myFunc()
+ {
+ simgrid::s4u::MutexPtr mutex = simgrid::s4u::Mutex::create(); // Too bad we cannot use `new`
+
+ mutex->lock(); // use the mutex as a simple reference
+ // bla bla
+ mutex->unlock();
+
+ } // The mutex gets automatically freed because the only existing reference gets out of scope
+
+API Reference
+*************
+
+.. _API_s4u_Activity:
+
+=============
+s4u::Activity
+=============
+
+.. doxygenclass:: simgrid::s4u::Activity
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Actor:
+
+==========
+s4u::Actor
+==========
+
+.. doxygentypedef:: ActorPtr
+
+.. doxygenclass:: simgrid::s4u::Actor
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Barrier:
+
+============
+s4u::Barrier
+============
+
+.. doxygentypedef:: BarrierPtr
+
+.. doxygenclass:: simgrid::s4u::Barrier
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Comm:
+
+=========
+s4u::Comm
+=========
+
+.. doxygentypedef:: CommPtr
+
+.. doxygenclass:: simgrid::s4u::Comm
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_ConditionVariable:
+
+======================
+s4u::ConditionVariable
+======================
+
+.. doxygentypedef:: ConditionVariablePtr
+
+.. doxygenclass:: simgrid::s4u::ConditionVariable
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Engine:
+
+===========
+s4u::Engine
+===========
+
+.. doxygenclass:: simgrid::s4u::Engine
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Exec:
+
+=========
+s4u::Exec
+=========
+
+.. doxygentypedef:: ExecPtr
+
+.. doxygenclass:: simgrid::s4u::Exec
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Host:
+
+=========
+s4u::Host
+=========
+
+.. doxygenclass:: simgrid::s4u::Host
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Io:
+
+=======
+s4u::Io
+=======
+
+.. doxygentypedef:: IoPtr
+
+.. doxygenclass:: simgrid::s4u::Io
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Link:
+
+=========
+s4u::Link
+=========
+
+.. doxygenclass:: simgrid::s4u::Link
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Mailbox:
+
+============
+s4u::Mailbox
+============
+
+.. doxygentypedef:: MailboxPtr
+
+.. doxygenclass:: simgrid::s4u::Mailbox
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Mutex:
+
+==========
+s4u::Mutex
+==========
+
+.. doxygentypedef:: MutexPtr
+
+.. doxygenclass:: simgrid::s4u::Mutex
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_NetZone:
+
+============
+s4u::NetZone
+============
+
+.. doxygenclass:: simgrid::s4u::NetZone
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Semaphore:
+
+==============
+s4u::Semaphore
+==============
+
+.. doxygentypedef:: SemaphorePtr
+
+.. doxygenclass:: simgrid::s4u::Semaphore
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_Storage:
+
+============
+s4u::Storage
+============
+
+.. doxygenclass:: simgrid::s4u::Storage
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_VirtualMachine:
+
+===================
+s4u::VirtualMachine
+===================
+
+.. doxygenclass:: simgrid::s4u::VirtualMachine
+ :members:
+ :protected-members:
+ :undoc-members:
+
+.. _API_s4u_this_actor:
+
+=========================
+namespace s4u::this_actor
+=========================
+.. doxygennamespace:: simgrid::s4u::this_actor
