X-Git-Url: http://bilbo.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/8f58249ee1e3d4fff121c049fc018bf6fa9555a8..5edec65e26d76490b9753d8db950a8a2ddf3cb2c:/docs/source/Platform_examples.rst diff --git a/docs/source/Platform_examples.rst b/docs/source/Platform_examples.rst index b9f8e1d280..29b481d61d 100644 --- a/docs/source/Platform_examples.rst +++ b/docs/source/Platform_examples.rst @@ -15,6 +15,8 @@ Network Topology Examples ========================= +.. _platform_example_3hosts: + Simple Example with 3 hosts --------------------------- @@ -48,53 +50,53 @@ 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. +There is often more than one way to model a given platform. For example, the above platform could also be +:ref:`expressed using a shortest path algorithm ` instead of explicitely listing all routes as in +the example above. + Cluster with a Crossbar ----------------------- -A very common parallel computing platform is a homogeneous cluster in -which hosts are interconnected via a crossbar switch with as many -ports as hosts, so that any disjoint pairs of hosts can communicate -concurrently at full speed. For instance: +A very common parallel computing platform is a homogeneous cluster in which hosts are interconnected via a crossbar switch +with as many ports as hosts, so that any disjoint pairs of hosts can communicate concurrently at full speed. Because there +is no contention on the switch, it is modeled as if there were a direct link from each host to the outgoing router. For +instance: + .. literalinclude:: ../../examples/platforms/cluster_crossbar.xml :language: xml :lines: 1-3,18- -One specifies a name prefix and suffix for each host, and then give an -integer range. In the example the cluster contains 65535 hosts (!), -named ``node-0.simgrid.org`` to ``node-65534.simgrid.org``. All hosts -have the same power (1 Gflop/sec) and are connected to the switch via -links with same bandwidth (125 MBytes/sec) and latency (50 +One specifies a name prefix and suffix for each host, and then give an integer range. In the example the cluster contains +65536 hosts (!), named ``node-0.simgrid.org`` to ``node-65535.simgrid.org``. All hosts have the same power (1 Gflop/sec) +and are connected directly to the switch via private links with same bandwidth (125 MBytes/sec) and latency (50 microseconds). -.. todo:: +The outgoing router is named ``${prefix}${cluster_id}_router${suffix}`` so in this case, this is +``node-cluster-crossbar_router.simgrid.org``. - Add the picture. +.. image:: ../../examples/platforms/cluster_crossbar.svg + :align: center Cluster with a Shared Backbone ------------------------------ -Another popular model for a parallel platform is that of a set of -homogeneous hosts connected to a shared communication medium, a -backbone, with some finite bandwidth capacity and on which -communicating host pairs can experience contention. For instance: - +Another popular model for a parallel platform is that of a set of homogeneous hosts connected to a shared communication +medium, a backbone, with some limited bandwidth capacity and on which communicating host pairs can experience contention. +For instance: .. literalinclude:: ../../examples/platforms/cluster_backbone.xml :language: xml :lines: 1-3,18- -The only differences with the crossbar cluster above are the ``bb_bw`` -and ``bb_lat`` attributes that specify the backbone characteristics -(here, a 500 microseconds latency and a 2.25 GByte/sec -bandwidth). This link is used for every communication within the -cluster. The route from ``node-0.simgrid.org`` to ``node-1.simgrid.org`` -counts 3 links: the private link of ``node-0.simgrid.org``, the backbone -and the private link of ``node-1.simgrid.org``. - -.. todo:: +The main differences with the crossbar cluster above are the ``bb_bw`` and ``bb_lat`` attributes that specify the backbone +characteristics (here, a 500 microseconds latency and a 2.25 GBytes/sec bandwidth). This link is used for every +communication within the cluster. The route from ``node-0.simgrid.org`` to ``node-1.simgrid.org`` counts 3 links: the +private link of ``node-0.simgrid.org``, the backbone and the private link of ``node-1.simgrid.org``. The route from +``node-0.simgrid.org`` to the outer internet counts 2 links: the private link of ``node-0.simgrid.org`` and the backbone. - Add the picture. +.. image:: ../../examples/platforms/cluster_backbone.svg + :align: center Torus Cluster ------------- @@ -130,8 +132,8 @@ cluster (and thus reduce its price) while maintaining a high bisection bandwidth and a relatively low diameter. To model this in SimGrid, pass a ``topology="FAT_TREE"`` attribute to your cluster. The ``topo_parameters=#levels;#downlinks;#uplinks;link count`` follows the -semantic introduced in the `Figure 1B of this article -`_. +semantic introduced in the `Figure 1(b) of this article +`_. Here is the meaning of this example: ``2 ; 4,4 ; 1,2 ; 1,2`` @@ -191,10 +193,10 @@ For example, ``3,4 ; 3,2 ; 3,1 ; 2``: Star Zone --------- -In a Star topology, as the name says, nodes are organized following a star. -It's similar to a cluster topology but you have the flexibility to set -different route for every component in the star. -Unfortunately, it's only available in the C++ interface. +A Star topology can be seen as a crossbar cluster that does not interconnect hosts, but subzones. It can for example be +used to model a cluster of complex hosts, where each host is disaggregated, with CPUs, GPUs and maybe a network on chip. It +is similar to a cluster topology, with the flexibility to set different route for every component in the star. Because of +its complexity, this topology is only available from the C++ interface. .. image:: img/starzone.svg :scale: 80%