[simgrid.git] / docs / source / platform_reference.rst

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.. _platform_reference:
   
DTD Reference
*************

Your platform description should follow the specification presented in the 
`simgrid.dtd <https://simgrid.org/simgrid.dtd>`_ DTD file. The same DTD is used for both platform and deployment files. 

.. _pf_tag_config:

------------------------------------------------------------------
<config>
------------------------------------------------------------------

Adding configuration flags directly into the platform file becomes particularly useful when the realism of the described
platform depends on some specific flags. For example, this could help you to finely tune SMPI. Almost all
:ref:`command-line configuration items <options_list>` can be configured this way.

Each configuration flag is described as a :ref:`pf_tag_prop` whose 'id' is the name of the flag and 'value' is what it
has to be set to.

**Parent tags:** :ref:`pf_tag_platform` (must appear before any other tags) |br|
**Children tags:** :ref:`pf_tag_prop` |br|
**Attributes:** none

.. code-block:: xml

   <?xml version = '1.0'?>
   <!DOCTYPE platform SYSTEM "https://simgrid.org/simgrid.dtd">
   <platform version = "4.1">
     <config>
       <prop id = "maxmin/precision" value = "0.000010" />
       <prop id = "cpu/optim" value = "TI" />
       <prop id = "network/model" value = "SMPI" />
       <prop id = "smpi/bw-factor" value = "65472:0.940694;15424:0.697866;9376:0.58729" />
     </config>

     <!-- The rest of your platform -->
   </platform>

|hr|
   
.. _pf_tag_host:

------------------------------------------------------------------
<host>
------------------------------------------------------------------

A host is the computing resource on which an actor can run. See :cpp:class:`simgrid::s4u::Host`.

**Parent tags:** :ref:`pf_tag_zone` (only leaf zones, i.e., zones containing neither inner zones nor clusters) |br|
**Children tags:** :ref:`pf_tag_mount`, :ref:`pf_tag_prop`, :ref:`pf_tag_storage` |br|
**Attributes:**

:``id``: Host name.
   Must be unique over the whole platform.
:``speed``: Computational power (per core, in flop/s).
   If you use DVFS, provide a comma-separated list of values for each pstate (see :ref:`howto_dvfs`).
:``core``: Amount of cores (default: 1).
   See :ref:`howto_multicore`.
:``availability_file``:
   File containing the availability profile.
   Almost every lines of such files describe timed events as ``date ratio``.
   Example:

   .. code-block:: python

      1 0.5
      2 0.2
      5 1
      LOOPAFTER 5

   - At time t = 1, half of the host computational power (0.5 means 50%) is used to process some background load, hence 
     only 50% of this initial power remains available to your own simulation. 
   - At time t = 2, the available power drops at 20% of the initial value.
   - At time t = 5, the host can compute at full speed again.
   - At time t = 10, the profile is reset (as we are 5 seconds after the last event). Then the available speed will drop
     again to 50% at time t = 11.

   If your profile does not contain any LOOPAFTER line, then it will be executed only once and not in a repetitive way.

   .. warning:: Don't get fooled: Bandwidth and Latency profiles of a :ref:`pf_tag_link` contain absolute values, while
      Availability profiles of a :ref:`pf_tag_host` contain ratios.
:``state_file``: File containing the state profile.
   Almost every lines of such files describe timed events as ``date boolean``.
   Example:

   .. code-block:: python

      1 0
      2 1
      LOOPAFTER 8

   - At time t = 1, the host is turned off (a zero value means OFF)
   - At time t = 2, the host is turned back on (any other value than zero means ON)
   - At time t = 10, the profile is reset (as we are 8 seconds after the last event). Then the host will be turned off 
     again at time t = 11.

   If your profile does not contain any LOOPAFTER line, then it will be executed only once and not in a repetitive way.

:``coordinates``: Vivaldi coordinates (meaningful for Vivaldi zones only).
   See :ref:`pf_tag_peer`.
:``pstate``: Initial pstate (default: 0, the first one).
   See :ref:`howto_dvfs`.

|hr|
   
.. _pf_tag_link:

------------------------------------------------------------------
<link>
------------------------------------------------------------------

SimGrid links usually represent one-hop network connections (see :cpp:class:`simgrid::s4u::Link`), i.e., a single wire. 
They can also be used to abstract a larger network interconnect, e.g., the entire transcontinental network, into a 
single element.

**Parent tags:** :ref:`pf_tag_zone` (both leaf zones and inner zones) |br|
**Children tags:** :ref:`pf_tag_prop` |br|
**Attributes:**

:``id``:  Link name. Must be unique over the whole platform.
:``bandwidth``: Maximum bandwidth for this link. You must specify a unit as follows.

   **Units in bytes and powers of 2** (1 KiBps = 1,024 Bps):
     Bps, KiBps, MiBps, GiBps, TiBps, PiBps, or EiBps. |br|
   **Units in bits  and powers of 2** (1 Bps = 8 bps):
     bps, Kibps, Mibps, Gibps, Tibps, Pibps, or Eibps. |br|
   **Units in bytes and powers of 10**  (1 KBps = 1,000 Bps):
     Bps, KBps, MBps, GBps, TBps, PBps, or EBps. |br|
   **Units in bits  and powers of 10:**
     bps, Kbps, Mbps, Gbps, Tbps, Pbps, or Ebps.

:``latency``: Latency for this link (default: 0.0). You must specify a unit as follows.

   ==== =========== ======================
   Unit Meaning     Duration in seconds
   ==== =========== ======================
   ps   picosecond  10⁻¹² = 0.000000000001
   ns   nanosecond  10⁻⁹ = 0.000000001
   us   microsecond 10⁻⁶ = 0.000001
   ms   millisecond 10⁻³ = 0.001
   s    second      1
   m    minute      60
   h    hour        60 * 60
   d    day         60 * 60 * 24
   w    week        60 * 60 * 24 * 7
   ==== =========== ======================

:``sharing_policy``: Sharing policy for the link. Possible values are ``SHARED``, ``FATPIPE`` or ``SPLITDUPLEX``
   (default: ``SHARED``).

   If set to ``SHARED``, the available bandwidth is fairly shared among all the flows traversing this link. This tend to
   model the bandwidth sharing behavior of the UDP or TCP protocols.

   If set to ``FATPIPE``, flows have no impact on each other, hence each flow can exploit the full bandwidth of this
   link. This aims at modeling the behavior of the Internet backbones that cannot get saturated by your application.
   What you experience of such networks usually is their latency only.

   If set to ``SPLITDUPLEX``, the link models cross-traffic
   effects. Under the ``SHARED`` policy, two flows of reverse
   direction share the same resource, and can only get half of the
   bandwidth each. But TCP connections are full duplex, meaning that
   all both directions can get the full bandwidth. To model this, any
   link under the ``SPLITDUPLEX`` policy is split in two links (their
   names are suffixed with "_UP" and "_DOWN"). You must then specify
   which direction gets actually used when referring to that link in a
   :ref:`pf_tag_link_ctn`.
        
:``bandwidth_file``: File containing the bandwidth profile.
   Almost every lines of such files describe timed events as ``date
   bandwidth`` (in bytes per second).
   Example:

   .. code-block:: python

      4.0 40000000
      8.0 60000000
      LOOPAFTER 12.0

   - At time t=4, the bandwidth is of 40 MBps.
   - At time t=8, it raises to 60MBps.
   - At time t=24, it drops at 40 MBps again.

   .. warning:: Don't get fooled: Bandwidth and Latency profiles of a
      :ref:`pf_tag_link` are absolute values, but Availability
      profiles of :ref:`pf_tag_host` are ratio.
:``latency_file``: File containing the latency profile.
   Almost every lines of such files describe timed events as ``date
   latency`` (in seconds).
   Example:
                   
   .. code-block:: python
                   
      1.0 0.001
      3.0 0.1
      LOOPAFTER 5.0

   - At time t=1, the latency is of 1ms (0.001 second)
   - At time t=3, the latency is of 100ms (0.1 second)
   - At time t=8 (5 seconds after the last event), the profile loops.
   - At time t=9 (1 second after the loop reset), the latency is back at 1ms.
      
   If your trace does not contain a LOOPAFTER line, then your profile
   is only executed once and not repetitively.
  
   .. warning:: Don't get fooled: Bandwidth and Latency profiles of a
      :ref:`pf_tag_link` are absolute values, but Availability
      profiles of :ref:`pf_tag_host` are ratio.
:``state_file``: File containing the state profile. See :ref:`pf_tag_host`.

|hr|

.. _pf_tag_peer:

------------------------------------------------------------------
<peer>
------------------------------------------------------------------

This tag represents a peer, as in Peer-to-Peer (P2P) networks. It is
handy to model situations where hosts have an asymmetric
connectivity. Computers connected through set-to-boxes usually have a
much better download rate than their upload rate.  To model this,
<peer> creates and connects several elements: an host, an upload link
and a download link.

**Parent tags:** :ref:`pf_tag_zone` (only with Vivaldi routing) |br|
**Children tags:** none |br|
**Attributes:**

:``id``: Name of the host. Must be unique on the whole platform.
:``speed``: Computational power (in flop/s).
   If you use DVFS, provide a comma-separated list of values for each pstate (see :ref:`howto_dvfs`). 
:``bw_in``: Bandwidth of the private downstream link, along with its
            unit. See :ref:`pf_tag_link`.
:``bw_out``: Bandwidth of the private upstream link, along with its
             unit. See :ref:`pf_tag_link`.
:``lat``: Latency of both private links. See :ref:`pf_tag_link`.
:``coordinates``: Coordinates of the gateway for this peer.

   The communication latency between an host A=(xA,yA,zA) and an host
   B=(xB,yB,zB) is computed as follows:
 
   latency = sqrt( (xA-xB)² + (yA-yB)² ) + zA + zB

   See the documentation of
   :cpp:class:`simgrid::kernel::routing::VivaldiZone` for details on
   how the latency is computed from the coordinate, and on the the up
   and down bandwidth are used.
:``availability_file``: File containing the availability profile.
   See the full description in :ref:`pf_tag_host`
:``state_file``: File containing the state profile.
   See the full description in :ref:`pf_tag_host`

|hr|

.. _pf_tag_platform:

------------------------------------------------------------------
<platform>
------------------------------------------------------------------

**Parent tags:** none (this is the root tag of every file) |br|
**Children tags:** :ref:`pf_tag_config` (must come first),
:ref:`pf_tag_cluster`, :ref:`pf_tag_cabinet`, :ref:`pf_tag_peer`,
:ref:`pf_tag_zone`, :ref:`pf_tag_trace`, :ref:`pf_tag_trace_connect` |br|
**Attributes:** 

:``version``: Version of the DTD, describing the whole XML format.
              This versionning allow future evolutions, even if we
              avoid backward-incompatible changes. The current version
              is **4.1**. The ``simgrid_update_xml`` program can
              upgrade most of the past platform files to the recent
              formalism.

|hr|
              
.. _pf_tag_prop:

------------------------------------------------------------------
<prop>
------------------------------------------------------------------

This tag can be used to attach user-defined properties to some
platform elements. Both the name and the value can be any string of
your wish. You can use this to pass extra parameters to your code and
the plugins.

From your code, you can interact with these properties using the
following functions:

- Actor: :cpp:func:`simgrid::s4u::Actor::get_property` or :cpp:func:`MSG_process_get_property_value`
- Cluster: this is a zone, see below.
- Host: :cpp:func:`simgrid::s4u::Host::get_property` or :cpp:func:`MSG_host_get_property_value`
- Link: :cpp:func:`simgrid::s4u::Link::get_property`
- Storage: :cpp:func:`simgrid::s4u::Storage::get_property` or :cpp:func:`MSG_storage_get_property_value`
- Zone: :cpp:func:`simgrid::s4u::Zone::get_property` of :cpp:func:`MSG_zone_get_property_value`

**Parent tags:** :ref:`pf_tag_actor`, :ref:`pf_tag_config`, :ref:`pf_tag_cluster`, :ref:`pf_tag_host`,
:ref:`pf_tag_link`, :ref:`pf_tag_storage`, :ref:`pf_tag_zone` |br|
**Children tags:** none |br|
**Attributes:**

:``id``: Name of the defined property.
:``value``: Value of the defined property.

|hr|

.. _pf_tag_router:

------------------------------------------------------------------
<router>
------------------------------------------------------------------

A router is similar to an :ref:`pf_tag_host`, but it cannot contain
any actor. It is only useful to some routing algorithms. In
particular, they are useful when you want to use the NS3 bindings to
break the routes that are longer than 1 hop.

**Parent tags:** :ref:`pf_tag_zone` (only leaf zones, i.e. zones containing no inner zones nor clusters) |br|
**Children tags:** :ref:`pf_tag_prop`, :ref:`pf_tag_storage` |br|
**Attributes:**

:``id``: Router name.
   No other host or router may have the same name over the whole platform.
:``coordinates``: Vivaldi coordinates. See :ref:`pf_tag_peer`.      

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