=====================
SimGrid was conceived as a tool to study distributed algorithms. Its
-modern S4U interface makes it easy to assess Cloud, P2P, HPC, IoT and
-similar settings.
-
-A typical SimGrid simulation is composed of several **Actors**
-|api_s4u_Actor|_ , that execute user-provided functions. The actors
-have to explicitly use the S4U interface to express their computation,
-communication, disk usage and other **Activities** |api_s4u_Activity|_
-, so that they get reflected within the simulator. These activities
-take place on **Resources** (CPUs, links, disks). SimGrid predicts the
-time taken by each activity and orchestrates accordingly the actors
-waiting for the completion of these activities.
-
-.. |api_s4u_Actor| image:: /images/extlink.png
- :align: middle
- :width: 12
-.. _api_s4u_Actor: api/classsimgrid_1_1s4u_1_1Actor.html#class-documentation
+modern :ref:`S4U interface <S4U_doc>` makes it easy to assess Cloud,
+P2P, HPC, IoT and similar settings.
-.. |api_s4u_Activity| image:: /images/extlink.png
- :align: middle
- :width: 12
-.. _api_s4u_Activity: api/classsimgrid_1_1s4u_1_1Activity.html#class-documentation
+A typical SimGrid simulation is composed of several |Actors|_, that
+execute user-provided functions. The actors have to explicitly use the
+S4U interface to express their computation, communication, disk usage
+and other |Activities|_, so that they get reflected within the
+simulator. These activities take place on **Resources** (|Hosts|_,
+|Links|_, |Storages|_). SimGrid predicts the time taken by each
+activity and orchestrates accordingly the actors waiting for the
+completion of these activities.
+Each actor executes a user-provided function on a simulated |Host|_
+with which it can interact. Communications are not directly sent to
+actors, but posted onto a |Mailbox|_ that serve as rendez-vous point
+between communicating actors.
-Each actor executes a user-provided function on a simulated **Host**
-|api_s4u_Host|_ with which it can interact. Communications are not
-directly sent to actors, but posted onto **Mailboxes**
-|api_s4u_Mailbox|_ that serve as rendez-vous points between
-communicating processes.
+.. |Actors| replace:: **Actors**
+.. _Actors: api/classsimgrid_1_1s4u_1_1Actor.html
-.. |api_s4u_Host| image:: /images/extlink.png
- :align: middle
- :width: 12
-.. _api_s4u_Host: api/classsimgrid_1_1s4u_1_1Host.html#class-documentation
+.. |Activities| replace:: **Activities**
+.. _Activities: api/classsimgrid_1_1s4u_1_1Activity.html
-.. |api_s4u_Mailbox| image:: /images/extlink.png
- :align: middle
- :width: 12
-.. _api_s4u_Mailbox: api/classsimgrid_1_1s4u_1_1Mailbox.html#class-documentation
+.. |Hosts| replace:: **Hosts**
+.. _Hosts: api/classsimgrid_1_1s4u_1_1Host.html
+
+.. |Links| replace:: **Links**
+.. _Links: api/classsimgrid_1_1s4u_1_1Link.html
+
+.. |Storages| replace:: **Storages**
+.. _Storages: api/classsimgrid_1_1s4u_1_1Storage.html
+
+.. |VirtualMachines| replace:: **VirtualMachines**
+.. _VirtualMachines: api/classsimgrid_1_1s4u_1_1VirtualMachine.html
+
+.. |Host| replace:: **Host**
+.. _Host: api/classsimgrid_1_1s4u_1_1Host.html
+
+.. |Link| replace:: **Link**
+.. _Link: api/classsimgrid_1_1s4u_1_1Link.html
+
+.. |Mailbox| replace:: **Mailbox**
+.. _Mailbox: api/classsimgrid_1_1s4u_1_1Mailbox.html
+
+.. |Barrier| replace:: **Barrier**
+.. _Barrier: api/classsimgrid_1_1s4u_1_1Barrier.html
+
+.. |ConditionVariable| replace:: **ConditionVariable**
+.. _ConditionVariable: api/classsimgrid_1_1s4u_1_1ConditionVariable.html
+
+.. |Mutex| replace:: **Mutex**
+.. _Mutex: api/classsimgrid_1_1s4u_1_1Mutex.html
+
+
+**In the remainder of this tutorial**, you will discover a simple yet
+fully functioning example of SimGrid simulation: the Master/Workers
+application. We will detail each part of the code and necessary
+configuration to make it working. After this tour, several exercises
+are proposed to let you discover some of the SimGrid features, hands
+on the keyboard. This practical session will be given in C++, that you
+are supposed to know beforehand.
Discover the Master/Workers
This section introduces a first example of SimGrid simulation. This
simple application is composed of two kind of actors: the **master**
is in charge of distributing some computational tasks to a set of
-**workers** that execute them.
+**workers** that execute them.
-.. image:: /images/tuto-masterworkers-intro.svg
+.. image:: /tuto_s4u/img/intro.svg
:align: center
We first present a round-robin version of this application, where the
:cpp:func:`simgrid::s4u::Mailbox::put`. Also, :c:macro:`XBT_INFO` is used
as a replacement to printf() or to cout to ensure that the messages
are nicely logged along with the simulated time and actor name.
-
-
+
+
.. literalinclude:: ../../examples/s4u/app-masterworkers/s4u-app-masterworkers-fun.cpp
:language: c++
:start-after: master-begin
Starting the Simulation
.......................
-
+
And this is it. In only a few lines, we defined the algorithm of our
master/workers examples.
Platform files define the virtual platform on which the provided
application will take place. In contains one or several **Network
-Zone** |api_s4u_NetZone|_ that contain both **Host-** |api_s4u_Host|_
-and **Link-** |api_s4u_Link|_ Resources, as well as routing
-information.
+Zone** |api_s4u_NetZone|_ that contain both |Host|_ and |Link|_
+Resources, as well as routing information.
Such files can get rather long and boring, so the example below is
only an excerpts of the full ``examples/platforms/small_platform.xml``
route between the hosts Tremblay and Fafard is given. This path
traverses 6 links (named 4, 3, 2, 0, 1 and 8). There are several
examples of platforms in the archive under ``examples/platforms``.
-
-.. |api_s4u_NetZone| image:: /images/extlink.png
+
+.. |api_s4u_NetZone| image:: /img/extlink.png
:align: middle
:width: 12
.. _api_s4u_NetZone: api/classsimgrid_1_1s4u_1_1NetZone.html#class-documentation
-.. |api_s4u_Link| image:: /images/extlink.png
+.. |api_s4u_Link| image:: /img/extlink.png
:align: middle
:width: 12
.. _api_s4u_Link: api/classsimgrid_1_1s4u_1_1Link.html#class-documentation
This time, we have all parts: once the program is compiled, we can
execute it as follows. Note how the XBT_INFO() requests turned into
informative messages.
-
+
.. literalinclude:: ../../examples/s4u/app-masterworkers/s4u-app-masterworkers.tesh
:language: shell
:start-after: s4u-app-masterworkers-fun
:prepend: $$$ ./masterworkers platform.xml deploy.xml
:append: $$$
:dedent: 2
-
+
Improve it Yourself
-------------------
whether this is a good algorithm to dispatch tasks to the workers.
This very simple setting raises many interesting questions:
-.. image:: /images/tuto-masterworkers-question.svg
+.. image:: /tuto_s4u/img/question.svg
:align: center
- Which algorithm should the master use? Or should the worker decide
round-robin algorithm performs very well. Would it still hold true
when transfer time is not negligible? What if some tasks are
performed faster on some specific nodes?
-
+
- The network topology interconnecting the master and the workers
may be quite complicated. How does such a topology impact the
previous result?
concurrence and showing resource usage over a long period of time. It
was obtained with the Triva software.
-.. image:: /images/tuto-masterworkers-result.png
+.. image:: /tuto_s4u/img/result.png
:align: center
-Prerequisite
+Using Docker
............
-Before your proceed, you need to :ref:`install SimGrid <install>`, a
-C++ compiler and also ``pajeng`` to visualize the traces. The provided
-code template requires cmake to compile. On Debian and Ubuntu for
-example, you can get them as follows:
+The easiest way to take the tutorial is to use the dedicated Docker
+image. Once you `installed Docker itself
+<https://docs.docker.com/install/>`_, simply do the following:
+
+.. code-block:: shell
+
+ docker pull simgrid/tuto-s4u
+ docker run -it --rm --name simgrid --volume ~/simgrid-tutorial:/source/tutorial simgrid/tuto-s4u bash
+
+This will start a new container with all you need to take this
+tutorial, and create a ``simgrid-tutorial`` directory in your home on
+your host machine that will be visible as ``/source/tutorial`` within the
+container. You can then edit the files you want with your favorite
+editor in ``~/simgrid-tutorial``, and compile them within the
+container to enjoy the provided dependencies.
+
+.. warning::
+
+ Any change to the container out of ``/source/tutorial`` will be lost
+ when you log out of the container, so don't edit the other files!
+
+All needed dependencies are already installed in this container
+(SimGrid, a C++ compiler, cmake, pajeng and R). Vite being only
+optional in this tutorial, it is not installed to reduce the image
+size.
+
+The code template is available under ``/source/simgrid-template-s4u`` in
+the image. You should copy it to your working directory when you first
+log in:
+
+.. code-block:: shell
+
+ cp -r /source/simgrid-template-s4u/* /source/tutorial
+ cd /source/tutorial
+
+Using your Computer Natively
+............................
+
+To take the tutorial on your machine, you first need to :ref:`install
+SimGrid <install>`, a C++ compiler and also ``pajeng`` to visualize
+the traces. You may want to install `Vite
+<http://vite.gforge.inria.fr/>`_ to get a first glance at the
+traces. The provided code template requires cmake to compile. On
+Debian and Ubuntu for example, you can get them as follows:
.. code-block:: shell
- sudo apt install simgrid pajeng cmake g++
+ sudo apt install simgrid pajeng cmake g++ vite
An initial version of the source code is provided on framagit. This
template compiles with cmake. If SimGrid is correctly installed, you
make master-workers
./master-workers small_platform.xml master-workers_d.xml
-For a more "fancy" output, you can use simgrid-colorizer.
+For a more "fancy" output, you can use simgrid-colorizer.
.. code-block:: shell
``/opt/simgrid/bin/simgrid-colorizer``. If you did not install it at all,
you can find it in <simgrid_root_directory>/bin/colorize.
-.. todo::
+For a classical Gantt-Chart vizualisation, you can use `Vite
+<http://vite.gforge.inria.fr/>`_ if you have it installed, as
+follows. But do not spend too much time installing Vite, because there
+is a better way to visualize SimGrid traces (see below).
+
+.. code-block:: shell
+
+ ./master-workers small_platform.xml master-workers_d.xml --cfg=tracing:yes --cfg=tracing/msg/process:yes
+ vite simgrid.trace
+
+.. image:: /tuto_s4u/img/vite-screenshot.png
+ :align: center
+
+If you want the full power to visualize SimGrid traces, you need
+to use R. As a start, you can download this `starter script
+<https://framagit.org/simgrid/simgrid/raw/master/docs/source/tuto_s4u/draw_gantt.R>`_
+and use it as follows:
+
+.. code-block:: shell
- Explain how to generate a Gantt-Chart with S4U and pajeng.
+ ./master-workers small_platform.xml master-workers_d.xml --cfg=tracing:yes --cfg=tracing/msg/process:yes
+ pj_dump --ignore-incomplete-links simgrid.trace | grep STATE > gantt.csv
+ Rscript draw_gantt.R gantt.csv
-Lab 1: Simpler deployments
+It produces a ``Rplots.pdf`` with the following content:
+
+.. image:: /tuto_s4u/img/Rscript-screenshot.png
+ :align: center
+
+
+Lab 1: Simpler Deployments
--------------------------
In the provided example, adding more workers quickly becomes a pain:
:language: xml
-Copy your ``master-workers.cpp`` into ``master-workers-exo1.cpp`` and
+Copy your ``master-workers.cpp`` into ``master-workers-lab1.cpp`` and
add a new executable into ``CMakeLists.txt``. Then modify your worker
function so that it gets its mailbox name not from the name of its
host, but from the string passed as ``args[1]``. The master will send
...
}
-
+
Wrap up
.......
the involved parties.
Please refer to the full `API of Mailboxes
-<api/classsimgrid_1_1s4u_1_1Mailbox.html#class-documentation>`_
-|api_s4u_Mailbox|_ for more details.
+<api/classsimgrid_1_1s4u_1_1Mailbox.html#class-documentation>`_ for
+more details.
-Lab 2: Using the whole platform
--------------------------
+Lab 2: Using the Whole Platform
+-------------------------------
It is now easier to add a new worker, but you still has to do it
manually. It would be much easier if the master could start the
....................................
For that, the master needs to retrieve the list of hosts declared in
-the platform with :cpp:func:`simgrid::s4u::Engine::get_all_host()`.
-Then, the master should start the worker processes with
+the platform with :cpp:func:`simgrid::s4u::Engine::get_all_hosts`.
+Then, the master should start the worker actors with
:cpp:func:`simgrid::s4u::Actor::create`.
``Actor::create(name, host, func, params...)`` is a very flexible
mailbox they should use. We can still do so: the master should build
such a parameter before using it in the ``Actor::create()`` call. The
master could even pass directly the mailbox as a parameter to the
-workers.
+workers.
Since we want later to study concurrent applications, it is advised to
use a mailbox name that is unique over the simulation even if there is
-more than one master.
+more than one master.
One possibility for that is to use the actor ID (aid) of each worker
as a mailbox name. The master can retrieve the aid of the newly
mailbox, which should be passed as parameter to the workers. This
reduces the amount of mailboxes, but prevents the master from taking
any scheduling decision. It really depends on how you want to organize
-your application and what you want to study with your simulator.
+your application and what you want to study with your simulator. In
+this tutorial, that's probably not a good idea.
Wrap up
.......
in XML instead of using a programming interface: it forces a clear
separation of concerns between things of very different nature.
-Lab 3: Fixed experiment duration
+Lab 3: Fixed Experiment Duration
--------------------------------
In the current version, the number of tasks is defined through the
or you may kill them forcefully with
:cpp:func:`simgrid::s4u::Actor::kill` (if you already have a reference
to the actor you want to kill) or
-:cpp:func:`simgrid::s4u::Actor::kill(aid_t)` (if you only have its ID).
+:cpp:func:`void simgrid::s4u::Actor::kill(aid_t)` (if you only have its ID).
Anyway, the new deployment `deployment3.xml` file should thus look
.................................
Not all messages are equally informative, so you probably want to
-change most of the ``XBT_INFO`` into ``XBT_DEBUG`` so that they are hidden
-by default. You could for example show only the total number of tasks
-processed by default. You can still see the debug messages as follows:
+change some of the ``XBT_INFO`` into ``XBT_DEBUG`` so that they are
+hidden by default. For example, you may want to use ``XBT_INFO`` once
+every 100 tasks and ``XBT_DEBUG`` when sending all the other tasks. Or
+you could show only the total number of tasks processed by
+default. You can still see the debug messages as follows:
.. code-block:: shell
- ./masterworker examples/platforms/small_platform.xml deployment3.xml --log=msg_test.thres:debug
+ ./master-workers-lab3 small_platform.xml deployment3.xml --log=msg_test.thres:debug
-Lab 4: Understanding competing applications
--------------------------------------------
+Lab 4: Competing Applications
+-----------------------------
It is now time to start several applications at once, with the following ``deployment4.xml`` file.
understand which task belong to which application. To fix this, we
will categorize the tasks.
-For that, first let each master create its own category of tasks with
-@ref TRACE_category(), and then assign this category to each task using
-@ref MSG_task_set_category().
+Instead of starting the execution in one function call only with
+``this_actor::execute(cost)``, you need to
+create the execution activity, set its tracing category, and then start
+it and wait for its completion, as follows:
-The outcome can then be visualized as a Gantt-chart as follows:
+.. code-block:: cpp
-.. code-block:: shell
+ simgrid::s4u::ExecPtr exec = simgrid::s4u::this_actor::exec_init(compute_cost);
+ exec->set_tracing_category(category);
+ // exec->start() is optional here as wait() starts the activity on need
+ exec->wait();
- ./masterworker examples/platforms/small_platform.xml deployment4.xml --cfg=tracing:yes --cfg=tracing/msg/process:yes
- vite simgrid.trace
+You can make the same code shorter as follows:
-.. todo::
+.. code-block:: cpp
- Make it work
+ simgrid::s4u::this_actor::exec_init(compute_cost)->set_tracing_category(category)->wait();
-Going further
-.............
+Visualizing the result
+.......................
vite is not enough to understand the situation, because it does not
-deal with categorization. That is why you should switch to R to
-visualize your outcomes, as explained on `this page
+deal with categorization. This time, you absolutely must switch to R,
+as explained on `this page
<http://simgrid.gforge.inria.fr/contrib/R_visualization.php>`_.
+.. todo::
+
+ Include here the minimal setting to view something in R.
+
+
+Lab 5: Better Scheduling
+------------------------
+
+You don't need a very advanced visualization solution to notice that
+round-robin is completely suboptimal: most of the workers keep waiting
+for more work. We will move to a First-Come First-Served mechanism
+instead.
+
+For that, your workers should explicitely request for work with a
+message sent to a channel that is specific to their master. The name
+of that private channel can be the one used to categorize the
+executions, as it is already specific to each master.
+
+The master should serve in a round-robin manner the requests it
+receives, until the time is up. Changing the communication schema can
+be a bit hairy, but once it works, you will see that such as simple
+FCFS schema allows to double the amount of tasks handled over time
+here. Things may be different with another platform file.
+
+Further Improvements
+....................
+
+From this, many things can easily be added. For example, you could:
+
+- Allow workers to have several pending requests so as to overlap
+ communication and computations as much as possible. Non-blocking
+ communication will probably become handy here.
+- Add a performance measurement mechanism, enabling the master to make smart scheduling choices.
+- Test your code on other platforms, from the ``examples/platforms``
+ directory in your archive.
+
+ What is the largest number of tasks requiring 50e6 flops and 1e5
+ bytes that you manage to distribute and process in one hour on
+ ``g5k.xml`` ?
+- Optimize not only for the amount of tasks handled, but also for the
+ total energy dissipated.
+- And so on. If you come up with a really nice extension, please share
+ it with us so that we can extend this tutorial.
+
+After this Tutorial
+-------------------
+
+This tutorial is now terminated. You could keep reading the [online documentation][fn:4] or
+[tutorials][fn:7], or you could head up to the example section to read some code.
+
+.. todo::
+
+ TODO: Points to improve for the next time
+ - Propose equivalent exercises and skeleton in java.
+ - Propose a virtualbox image with everything (simgrid, pajeng, ...) already set up.
+ - Ease the installation on mac OS X (binary installer) and windows.
.. LocalWords: SimGrid
