Simple Example with 3 hosts
...........................
-At the most basic level, you can describe your simulated platform as a
-graph of hosts and network links. For instance:
+Imagine you want to describe a little platform with three hosts,
+interconnected as follows:
.. image:: /tuto_smpi/3hosts.png
:align: center
+This can be done with the following platform file, that considers the
+simulated platform as a graph of hosts and network links.
+
.. literalinclude:: /tuto_smpi/3hosts.xml
:language: xml
-Note the way in which hosts, links, and routes are defined in
-this XML. All hosts are defined with a speed (in Gflops), and links
-with a latency (in us) and bandwidth (in MBytes per second). Other
-units are possible and written as expected. Routes specify the list of
-links encountered from one route to another. Routes are symmetrical by
-default.
+The elements basic elements (with :ref:`pf_tag_host` and
+:ref:`pf_tag_link`) are described first, and then the routes between
+any pair of hosts are explicitely given with :ref:`pf_tag_route`. Any
+host must be given a computational speed (in flops) while links must
+be given a latency (in seconds) and a bandwidth (in bytes per
+second). Note that you can write 1Gflops instead of 1000000000flops,
+and similar. Last point: :ref:`pf_tag_route`s are symmetrical by
+default (but this can be changed).
Cluster with a Crossbar
.......................
sudo apt install simgrid pajeng make gcc g++ gfortran vite
-For R analysis of the produced traces, you may want to install R,
-and the `pajengr<https://github.com/schnorr/pajengr#installation/>_ package.
+For R analysis of the produced traces, you may want to install R,
+and the `pajengr <https://github.com/schnorr/pajengr#installation/>`_ package.
.. code-block:: shell
the documentation is up-to-date.
Lab 3: Execution Sampling on Matrix Multiplication example
--------------------------------
+----------------------------------------------------------
The second method to speed up simulations is to sample the computation
parts in the code. This means that the person doing the simulation
.. literalinclude:: /tuto_smpi/gemm_mpi.cpp
:language: c
:lines: 4-19
-
.. code-block:: shell
$ smpicc -O3 gemm_mpi.cpp -o gemm
$ time smpirun -np 16 -platform cluster_crossbar.xml -hostfile cluster_hostfile --cfg=smpi/display-timing:yes --cfg=smpi/running-power:1000000000 ./gemm
-
+
This should end quite quickly, as the size of each matrix is only 1000x1000.
But what happens if we want to simulate larger runs ?
Replace the size by 2000, 3000, and try again.
Lab 4: Memory folding on large allocations
--------------------------------
+------------------------------------------
Another issue that can be encountered when simulation with SMPI is lack of memory.
Indeed we are executing all MPI processes on a single node, which can lead to crashes.
