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 processes.
+between communicating actors.
.. |Actors| replace:: **Actors**
.. _Actors: api/classsimgrid_1_1s4u_1_1Actor.html
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:: /tuto_s4u/img/intro.svg
:align: center
: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.
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:: /img/extlink.png
:align: middle
:width: 12
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
-------------------
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?
.. code-block:: shell
docker pull simgrid/tuto-s4u
- docker run -it --rm --name simgrid --volume ~/simgrid-tutorial:/src/tutorial simgrid/tuto-s4u bash
+ 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 ``/src/tutorial`` within the
+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 ``/src/tutorial`` will be lost
+ 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
optional in this tutorial, it is not installed to reduce the image
size.
-The code template is available under ``/src/simgrid-template-s4u`` in
+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 /src/simgrid-template-s4u/* /src/tutorial
- cd /src/tutorial
+ cp -r /source/simgrid-template-s4u/* /source/tutorial
+ cd /source/tutorial
Using your Computer Natively
............................
Please compile and execute the provided simulator as follows:
-
.. code-block:: shell
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
.. 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>`_
...
}
-
+
Wrap up
.......
For that, the master needs to retrieve the list of hosts declared in
the platform with :cpp:func:`simgrid::s4u::Engine::get_all_hosts`.
-Then, the master should start the worker processes with
+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
.. todo::
Include here the minimal setting to view something in R.
-
+
Lab 5: Better Scheduling
------------------------
- 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.
+ 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.
+ it with us so that we can extend this tutorial.
After this Tutorial
-------------------
