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?
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
.......
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
-------------------
