-.. _platform:
-
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+.. _platform:
+
Describing your Simulated Platform
##################################
the :ref:`lua bindings <platform_lua>` (it is not yet possible to do so in
python or directly in C++).
-We understand that writing a complex platform description can be tricky, we thus included
-:ref:`many examples <platform_examples>` in the archive. This
-documentation also contains some :ref:`hints and howtos <howto>`, as well
-as the full :ref:`XML reference guide <platform_reference>`.
-
-
-Any simulated platform must contain **basic elements**, such as hosts, links, disks, etc. SimGrid gives you a great
-liberty when defining the **routing of your platform**, i.e., the network path taken between each pair of hosts.
+Any simulated platform must contain **basic elements**, such as
+:ref:`pf_tag_host`, :ref:`pf_tag_link`, :ref:`pf_tag_disk`, and similar.
+SimGrid makes no assumption about the **routing of your platform**, so you must declare
+explicitly the network path taken between each pair of hosts.
+This can be done through a flat list of :ref:`pf_tag_route` for each pair of hosts (routes
+are symmetrical by default), or you may use the advanced concept of :ref:`networking zone <platform_routing>`
+to efficiently express the routing of your platform.
Finally, you may also describe an **experimental scenario**, with qualitative (e.g., bandwidth variations representing
an external load) and qualitative (e.g., representing how some elements fail and restart over time) changes.
-
-First Example
-*************
-
-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
-
-The most important elements are the basic ones: :ref:`pf_tag_host`,
-:ref:`pf_tag_link`, and similar. Then come the routes between any pair
-of hosts, that are given explicitly with :ref:`pf_tag_route` (routes
-are symmetrical by default). 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.
-
-Every platform element must be located within a given **networking
-zone** . Zones are in
-charge of the routing, see below.
-
-The last thing you must know on SimGrid platform files is that the
-root tag must be :ref:`pf_tag_platform`. If the ``version`` attribute
-does not match what SimGrid expects, you will be hinted to use to the
-``simgrid_update_xml`` utility to update your file.
-
-
-Defining a Routing
-******************
-
-Networking zones (:ref:`pf_tag_zone`) are used to factorize the description
-to reduce the size of your platform on disk and in memory. Then, when
-a host wants to communicate with another host belonging to the same
-zone, it is the zone's duty to find the list of links that are
-involved in the communication. In the above examples, since we use
-``routing="Full"``, all routes must be explicitly given using the
-:ref:`pf_tag_route` and :ref:`pf_tag_link_ctn` tags (this :ref:`routing
-model <pf_rm>` is both simple and inefficient :) It is OK to not
-specify each and every route between hosts, as long as you do not try
-to start a communication on any of the missing routes during your
-simulation.
-
-Any zone may contain sub-zones, allowing for a hierarchical
-decomposition of the platform. Routing can be made more efficient (as the
-inter-zone routing gets factored with :ref:`pf_tag_zoneroute`), and
-allows you to have more than one routing model in your platform. For
-example, you can have a coordinate-based routing for the WAN parts
-of your platforms, a full routing within each datacenter, and a highly
-optimized routing within each cluster of the datacenter. In this
-case, determining the route between two given hosts gets :ref:`routing_basics`
-"somewhat more complex" but SimGrid still computes
-these routes for you in a time- and space-efficient manner.
-Here is an illustration of these concepts:
-
-.. image:: img/zone_hierarchy.png
-
-Circles represent processing units and squares represent network
-routers. Bold lines represent communication links. The zone "AS2" models the core of a national network interconnecting a
-small flat cluster (AS4) and a larger hierarchical cluster (AS5), a
-subset of a LAN (AS6), and a set of peers scattered around the world
-(AS7).
-
-.. todo:: Add more examples, such as the cloud example described in
- previous paragraph
-
-Performance Profiles and Churn
-******************************
+The most efficient way to learn about platform description is to look at the
+:ref:`many examples <platform_examples>` included in the archive and described
+in the next section. This documentation also contains some :ref:`hints and
+howtos <howto>`, as well as the full :ref:`XML reference guide
+<platform_reference>`.
.. LocalWords: SimGrid
