[simgrid.git] / doc / options.doc

/*! \page options Simgrid options and configurations

\htmlinclude .options.doc.toc

\section options_simgrid_configuration Changing SimGrid's behavior

A number of options can be given at runtime to change the default
SimGrid behavior. In particular, you can change the default cpu and
network models...

\subsection options_simgrid_configuration_fullduplex Using Fullduplex

Experimental fullduplex support is now available on the svn branch. In order to fullduple to work your platform must have two links for each pair
of interconnected hosts, see an example here:
\verbatim
        simgrid_svn_sources/exemples/msg/gtnets/fullduplex-p.xml
\endverbatim

Using fullduplex support ongoing and incoming communication flows are
treated independently for most models. The exception is the LV08 model which 
adds 0.05 of usage on the opposite direction for each new created flow. This 
can be useful to simulate some important TCP phenomena such as ack compression. 

Running a fullduplex example:
\verbatim
        cd simgrid_svn_sources/exemples/msg/gtnets
        ./gtnets fullduplex-p.xml fullduplex-d.xml --cfg=fullduplex:1
\endverbatim

\subsection options_simgrid_configuration_gtnets Using GTNetS

It is possible to use a packet-level network simulator
instead of the default flow-based simulation. You may want to use such
an approach if you have doubts about the validity of the default model
or if you want to perform some validation experiments. At the moment,
we support the GTNetS simulator (it is still rather experimental
though, so leave us a message if you play with it). 


<i>
To enable GTNetS model inside SimGrid it is needed to patch the GTNetS simulator source code 
and build/install it from scratch
</i>

 - <b>Download and enter the recent downloaded GTNetS directory</b>

 \verbatim
 svn checkout svn://scm.gforge.inria.fr/svn/simgrid/contrib/trunk/GTNetS/
 cd GTNetS
 \endverbatim


 - <b>Use the following commands to unzip and patch GTNetS package to work within SimGrid.</b>

 \verbatim
 unzip gtnets-current.zip
 tar zxvf gtnets-current-patch.tgz 
 cd gtnets-current
 cat ../00*.patch | patch -p1
 \endverbatim

  - <b>OPTIONALLY</b> you can use a patch for itanium 64bit processor family.

  \verbatim
  cat ../AMD64-FATAL-Removed-DUL_SIZE_DIFF-Added-fPIC-compillin.patch | patch -p1
  \endverbatim

 - <b>Compile GTNetS</b>

   Due to portability issues it is possible that GTNetS does not compile in your architecture. The patches furnished in SimGrid SVN repository are intended for use in Linux architecture only. Unfortunately, we do not have the time, the money, neither the manpower to guarantee GTNetS portability. We advice you to use one of GTNetS communication channel to get more help in compiling GTNetS. 


 \verbatim
 ln -sf Makefile.linux Makefile
 make depend
 make debug
 \endverbatim


 - <b>NOTE</b> A lot of warnings are expected but the application should compile
 just fine. If the makefile insists in compiling some QT libraries
 please try a make clean before asking for help.


 - <b>To compile optimized version</b>

 \verbatim
 make opt
 \endverbatim


 - <b>Installing GTNetS</b>

 It is important to put the full path of your libgtsim-xxxx.so file when creating the symbolic link. Replace < userhome > by some path you have write access to.

 \verbatim
 ln -sf /<absolute_path>/gtnets_current/libgtsim-debug.so /<userhome>/usr/lib/libgtnets.so
 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/<userhome>/usr/lib/libgtnets.so
 mkdir /<userhome>/usr/include/gtnets
 cp -fr SRC/*.h /<userhome>/usr/include/gtnets
 \endverbatim


 - <b>Enable GTNetS support in SimGrid</b>
 
In order to enable gtnets with simgrid you have to give where is gtnets. (path to \<gtnets_path\>/lib and \<gtnets_path\>/include)

   \verbatim
   Since v3.4 (with cmake)
   cmake . -Dgtnets_path=/<userhome>/usr
   
   Until v3.4 (with autotools)
   ./configure --with-gtnets=/<userhome>/usr
   \endverbatim

 - <b>Once you have followed all the instructions for compiling and
   installing successfully you can activate this feature at 
   runntime with the following options:</b>

   \verbatim
   Since v3.4 (with cmake)
   cd simgrid
   make
   ctest -R gtnets
   
   Until v3.4 (with autotools)
   cd simgrid/example/msg/
   make
   make check
   \endverbatim


 - <b>Or try the GTNetS model dogbone example with</b>

 \verbatim
 gtnets/gtnets gtnets/onelink-p.xml gtnets/onelink-d.xml --cfg=network_model:GTNets
 \endverbatim

 
 A long version of this <a href="http://gforge.inria.fr/docman/view.php/12/6283/GTNetS HowTo.html">HowTo</a>  it is available 


 More about GTNetS simulator at <a href="http://www.ece.gatech.edu/research/labs/MANIACS/GTNetS/index.html">GTNetS Website</a>


 - <b>DISCLAIMER</b>
 The patches provided by us worked successfully with GTNetS found 
 <a href="http://www.ece.gatech.edu/research/labs/MANIACS/GTNetS/software/gtnets-current.zip">here</a>, 
 dated from 12th June 2008. Due to the discontinuing development of
 GTNetS it is impossible to precise a version number. We STRONGLY recommend you
 to download and install the GTNetS version found in SimGrid repository as explained above.
 



\subsection options_simgrid_configuration_alternate_network Using alternative flow models

The default simgrid network model uses a max-min based approach as
explained in the research report
<a href="ftp://ftp.ens-lyon.fr/pub/LIP/Rapports/RR/RR2002/RR2002-40.ps.gz">A Network Model for Simulation of Grid Application</a>.
Other models have been proposed and implemented since then (see for example 
<a href="http://mescal.imag.fr/membres/arnaud.legrand/articles/simutools09.pdf">Accuracy Study and Improvement of Network Simulation in the SimGrid Framework</a>)
and can be activated at runtime. For example:
\verbatim
./mycode platform.xml deployment.xml --cfg=workstation/model:compound --cfg=network/model:LV08 -cfg=cpu/model:Cas01
\endverbatim

Possible models for the network are currently "Constant", "CM02",
"LegrandVelho", "GTNets", Reno", "Reno2", "Vegas". Others will
probably be added in the future and many of the previous ones are
experimental and are likely to disappear without notice... To know the
list of the currently  implemented models, you should use the
--help-models command line option.

\verbatim
./masterslave_forwarder ../small_platform.xml deployment_masterslave.xml  --help-models
Long description of the workstation models accepted by this simulator:
  CLM03: Default workstation model, using LV08 and CM02 as network and CPU
  compound: Workstation model allowing you to use other network and CPU models
  ptask_L07: Workstation model with better parallel task modeling
Long description of the CPU models accepted by this simulator:
  Cas01_fullupdate: CPU classical model time=size/power
  Cas01: Variation of Cas01_fullupdate with partial invalidation optimization of lmm system. Should produce the same values, only faster
  CpuTI: Variation of Cas01 with also trace integration. Should produce the same values, only faster if you use availability traces
Long description of the network models accepted by this simulator:
  Constant: Simplistic network model where all communication take a constant time (one second)
  CM02: Realistic network model with lmm_solve and no correction factors
  LV08: Realistic network model with lmm_solve and these correction factors: latency*=10.4, bandwidth*=.92, S=8775
  Reno: Model using lagrange_solve instead of lmm_solve (experts only)
  Reno2: Model using lagrange_solve instead of lmm_solve (experts only)
  Vegas: Model using lagrange_solve instead of lmm_solve (experts only)
\endverbatim

\section options_tracing Tracing Simulations for Visualization

The trace visualization is widely used to observe and understand the behavior
of parallel applications and distributed algorithms. Usually, this is done in a
two-step fashion: the user instruments the application and the traces are
analyzed after the end of the execution. The visualization itself can highlights
unexpected behaviors, bottlenecks and sometimes can be used to correct
distributed algorithms. The SimGrid team has instrumented the library
in order to let users trace their simulations and analyze them. This part of the
user manual explains how the tracing-related features can be enabled and used
during the development of simulators using the SimGrid library.

\subsection options_tracing_howitworks How it works

For now, the SimGrid library is instrumented so users can trace the <b>platform
utilization</b> using the MSG, SimDAG and SMPI interface. This means that the tracing will
register how much power is used for each host and how much bandwidth is used for
each link of the platform. The idea with this type of tracing is to observe the
overall view of resources utilization in the first place, especially the
identification of bottlenecks, load-balancing among hosts, and so on.

The idea of the tracing facilities is to give SimGrid users to possibility to
classify MSG and SimDAG tasks by category, tracing the platform utilization
(hosts and links) for each of the categories. For that,
the tracing interface enables the declaration of categories and a function to
mark a task with a previously declared category. <em>The tasks that are not
classified according to a category are not traced</em>. Even if the user
does not specify any category, the simulations can still be traced in terms
of resource utilization by using a special parameter that is detailed below.

\subsection options_tracing_enabling Enabling using CMake

With the sources of SimGrid, it is possible to enable the tracing 
using the parameter <b>-Denable_tracing=ON</b> when the cmake is executed.
The section \ref options_tracing_functions describes all the functions available
when this Cmake options is activated. These functions will have no effect
if SimGrid is configured without this option (they are wiped-out by the
C-preprocessor).

\verbatim
$ cmake -Denable_tracing=ON .
$ make
\endverbatim

\subsection options_tracing_functions Tracing Functions

\li <b>\c TRACE_category (const char *category)</b>: This function should be used
to define a user category. The category can be used to differentiate the tasks
that are created during the simulation (for example, tasks from server1,
server2, or request tasks, computation tasks, communication tasks).
All resource utilization (host power and link bandwidth) will be
classified according to the task category. Tasks that do not belong to a
category are not traced. The color for the category that is being declared
is random (use next function to specify a color).

\li <b>\c TRACE_category_with_color (const char *category, const char *color)</b>: Same
as TRACE_category, but let user specify a color encoded as a RGB-like string with
three floats from 0 to 1. So, to specify a red color, the user can pass "1 0 0" as
color parameter. A light-gray color can be specified using "0.7 0.7 0.7" as color.

\li <b>\c TRACE_msg_set_task_category (m_task_t task, const char *category)</b>:
This function should be called after the creation of a MSG task, to define the
category of that task. The first parameter \c task must contain a task that was
created with the function \c MSG_task_create. The second parameter
\c category must contain a category that was previously defined by the function
\c TRACE_category.

\li <b>\c TRACE_sd_set_task_category (SD_task_t task, const char *category)</b>:
This function should be called after the creation of a SimDAG task, to define the
category of that task. The first parameter \c task must contain a task that was
created with the function \c MSG_task_create. The second parameter
\c category must contain a category that was previously defined by the function
\c TRACE_category.

\li <b>\c TRACE_[host|link]_variable_declare (const char *variable)</b>:
Declare a user variable that will be associated to host/link. A variable can
be used to trace user variables such as the number of tasks in a server,
the number of clients in an application (for hosts), and so on.

\li <b>\c TRACE_[host|link]_variable_[set|add|sub] (const char *[host|link], const char *variable, double value)</b>:
Set the value of a given user variable for a given host/link. The value
of this variable is always associated to the host/link. The host/link 
parameters should be its name as the one listed in the platform file.

\li <b>\c TRACE_[host|link]_variable_[set|add|sub]_with_time (double time, const char *[host|link], const char *variable, double value)</b>:
Same as TRACE_[host|link]_variable_[set|add|sub], but let user specify
the time used to trace it. Users can specify a time that is not the 
simulated clock time as defined by the core simulator. This allows
a fine-grain control of time definition, but should be used with 
caution since the trace can be inconsistent if resource utilization
traces are also traced.

\li <b>\c TRACE_link_srcdst_variable_[set|add|sub] (const char *src, const char *dst, const char *variable, double value)</b>:
Same as TRACE_link_variable_[set|add|sub], but now users specify a source and
destination hosts (as the names from the platform file). The tracing library
will get the corresponding route that connects those two hosts (src and dst) and
[set|add|sub] the value's variable for all the links of the route.

\li <b>\c TRACE_link_srcdst_variable_[set|add|sub]_with_time (double time, const char *src, const char *dst, const char *variable, double value)</b>: 
Same as TRACE_link_srcdst_variable_[set|add|sub], but user specify a time different from the simulated time.

\subsection options_tracing_options Tracing configuration Options

These are the options accepted by the tracing system of SimGrid:

\li <b>\c 
tracing
</b>:
  Safe switch. It activates (or deactivates) the tracing system.
  No other tracing options take effect if this one is not activated.

\li <b>\c
tracing/platform
</b>:
  Register the simulation platform in the trace file.

\li <b>\c
tracing/onelink_only
</b>:
  By default, the tracing system uses all routes in the platform file
  to re-create a "graph" of the platform and register it in the trace file.
  This option let the user tell the tracing system to use only the routes
  that are composed with just one link.

\li <b>\c 
tracing/categorized
</b>:
  It activates the categorized resource utilization tracing. It should
  be enabled if tracing categories are used by this simulator.

\li <b>\c 
tracing/uncategorized
</b>:
  It activates the uncategorized resource utilization tracing. Use it if
  this simulator do not use tracing categories and resource use have to be
  traced.

\li <b>\c 
tracing/filename
</b>:
  A file with this name will be created to register the simulation. The file
  is in the Paje format and can be analyzed using Triva or Paje visualization
  tools. More information can be found in these webpages:
     <a href="http://triva.gforge.inria.fr/">http://triva.gforge.inria.fr/</a>
     <a href="http://paje.sourceforge.net/">http://paje.sourceforge.net/</a>

\li <b>\c 
tracing/smpi
</b>:
  This option only has effect if this simulator is SMPI-based. Traces the MPI
  interface and generates a trace that can be analyzed using Gantt-like
  visualizations. Every MPI function (implemented by SMPI) is transformed in a
  state, and point-to-point communications can be analyzed with arrows.

\li <b>\c 
tracing/smpi/group
</b>:
  This option only has effect if this simulator is SMPI-based. The processes
  are grouped by the hosts where they were executed.

\li <b>\c 
tracing/msg/task
</b>:
  This option only has effect if this simulator is MSG-based. It traces the
  behavior of all categorized MSG tasks, grouping them by hosts.

\li <b>\c 
tracing/msg/process
</b>:
  This option only has effect if this simulator is MSG-based. It traces the
  behavior of all categorized MSG processes, grouping them by hosts. This option
  can be used to track process location if this simulator has process migration.


\li <b>\c 
triva/categorized:graph_categorized.plist
</b>:
  This option generates a graph configuration file for Triva considering
  categorized resource utilization.

\li <b>\c 
triva/uncategorized:graph_uncategorized.plist
</b>:
  This option generates a graph configuration file for Triva considering
  uncategorized resource utilization.

\subsection options_tracing_example Example of Instrumentation

A simplified example using the tracing mandatory functions.

\verbatim
int main (int argc, char **argv)
{
  MSG_global_init (&argc, &argv);

  //(... after deployment ...)

  //note that category declaration must be called after MSG_create_environment
  TRACE_category_with_color ("request", "1 0 0");
  TRACE_category_with_color ("computation", "0.3 1 0.4");
  TRACE_category ("finalize");

  m_task_t req1 = MSG_task_create("1st_request_task", 10, 10, NULL);
  m_task_t req2 = MSG_task_create("2nd_request_task", 10, 10, NULL);
  m_task_t req3 = MSG_task_create("3rd_request_task", 10, 10, NULL);
  m_task_t req4 = MSG_task_create("4th_request_task", 10, 10, NULL);
  TRACE_msg_set_task_category (req1, "request");
  TRACE_msg_set_task_category (req2, "request");
  TRACE_msg_set_task_category (req3, "request");
  TRACE_msg_set_task_category (req4, "request");

  m_task_t comp = MSG_task_create ("comp_task", 100, 100, NULL);
  TRACE_msg_set_task_category (comp, "computation");

  m_task_t finalize = MSG_task_create ("finalize", 0, 0, NULL);
  TRACE_msg_set_task_category (finalize, "finalize");

  //(...)

  MSG_clean();
  return 0;
}
\endverbatim

\subsection options_tracing_analyzing Analyzing the SimGrid Traces

The SimGrid library, during an instrumented simulation, creates a trace file in
the Paje file format that contains the platform utilization for the simulation
that was executed. The visualization analysis of this file is performed with the
visualization tool <a href="http://triva.gforge.inria.fr">Triva</a>, with
special configurations tunned to SimGrid needs. This part of the documentation
explains how to configure and use Triva to analyse a SimGrid trace file.

- <b>Installing Triva</b>: the tool is available in the INRIAGforge, 
at <a href="http://triva.gforge.inria.fr">http://triva.gforge.inria.fr</a>.
Use the following command to get the sources, and then check the file
<i>INSTALL</i>. This file contains instructions to install
the tool's dependencies in a Ubuntu/Debian Linux. The tool can also
be compiled in MacOSes natively, check <i>INSTALL.mac</i> file.
\verbatim
$ svn checkout svn://scm.gforge.inria.fr/svn/triva
$ cd triva
$ cat INSTALL
\endverbatim

- <b>Executing Triva</b>: a binary called <i>Triva</i> is available after the
  installation (you can execute it passing <em>--help</em> to check its
options). If the triva binary is not available after following the
installation instructions, you may want to execute the following command to
initialize the GNUstep environment variables. We strongly recommend that you
use the latest GNUstep packages, and not the packages available through apt-get
in Ubuntu/Debian packaging systems. If you install GNUstep using the latest
available packages, you can execute this command:
\verbatim
$ source /usr/GNUstep/System/Library/Makefiles/GNUstep.sh
\endverbatim
You should be able to see this output after the installation of triva:
\verbatim
$ ./Triva.app/Triva --help
Usage: Triva [OPTIONS...] TRACE0 [TRACE1]
Trace Analysis through Visualization

TimeInterval
    --ti_frequency {double}    Animation: frequency of updates
    --ti_hide                  Hide the TimeInterval window
    --ti_forward {double}      Animation: value to move time-slice
    --ti_apply                 Apply the configuration
    --ti_update                Update on slider change
    --ti_animate               Start animation
    --ti_start {double}        Start of time slice
    --ti_size {double}         Size of time slice
Triva
    --comparison               Compare Trace Files (Experimental)
    --graph                    Configurable Graph
    --list                     Print Trace Type Hierarchy
    --hierarchy                Export Trace Type Hierarchy (dot)
    --stat                     Trace Statistics and Memory Utilization
    --instances                List All Trace Entities
    --linkview                 Link View (Experimental)
    --treemap                  Squarified Treemap
    --merge                    Merge Trace Files (Experimental)
    --check                    Check Trace File Integrity
GraphConfiguration
    --gc_conf {file}           Graph Configuration in Property List Format
    --gc_apply                 Apply the configuration
    --gc_hide                  Hide the GraphConfiguration window
\endverbatim
Triva expects that the user choose one of the available options 
(currently <em>--graph</em> or <em>--treemap</em> for a visualization analysis)
and the trace file from the simulation.

- <b>Understanding Triva - time-slice</b>: the analysis of a trace file using
  the tool always takes into account the concept of the <em>time-slice</em>.
This concept means that what is being visualized in the screen is always
calculated considering a specific time frame, with its beggining and end
timestamp. The time-slice is configured by the user and can be changed
dynamically through the window called <em>Time Interval</em> that is opened
whenever a trace file is being analyzed. The next figure depicts the time-slice
configuration window.
In the top of the window, in the space named <i>Trace Time</i>,
the two fields show the beggining of the trace (which usually starts in 0) and
the end (that depends on the time simulated by SimGrid). The middle of the
window, in the square named <i>Time Slice Configuration</i>, contains the
aspects related to the time-slice, including its <i>start</i> and its
<i>size</i>. The gray rectangle in the bottom of this part indicates the 
<i>current time-slice</i> that is considered for the drawings. If the checkbox 
<i>Update Drawings on Sliders Change</i> is not selected, the button
<i>Apply</i> must be clicked in order to inform triva that the
new time-slice must be considered. The bottom part of the window, in the space
indicated by the square <i>Time Slice Animation</i> can be used to advance
the time-frame automatically. The user configures the amount of time that the
time-frame will forward and how frequent this update will happen. Once this is
configured, the user clicks the <i>Play</i> button in order to see the dynamic
changes on the drawings.
<center>
\htmlonly
<a href="triva-time_interval.png" border=0><img src="triva-time_interval.png" width="50%" border=0></a>
\endhtmlonly
</center>
<b>Remarks:</b> when the trace has too many hosts or links, the computation to
take into account a new time-slice can be expensive. When this happens, the
<i>Frequency</i> parameter, but also updates caused by change on configurations
when the checkbox <i>Update Drawings on Sliders
Change</i> is selected will not be followed.

- <b>Understanding Triva - graph</b>: this part of the documention explains how
  to analyze the traces using the graph view of Triva, when the user executes
the tool passing <em>--graph</em> as parameter. Triva opens three windows when
this parameter is used: the <i>Time Interval</i> window (previously described),
the <i>Graph Representation</i> window, and the <em>Graph Configuration</em>
window. The Graph Representation is the window where drawings take place.
Initially, it is completely white waiting for a proper graph configuration input
by the user. We start the description of this type of analysis by describing the
<i>Graph Configuration</i> window (depicted below). By using a particular
configuration, triva
can be used to customize the graph drawing according to
the SimGrid trace that was created with user-specific categories. Before delving
into the details of this customization, let us first explain the major parts of
the graph configuration window. The buttons located in the top-right corner can
be used to delete, copy and create a new configuration. The checkbox in the
top-middle part of the window indicates if the configuration typed in the
textfield is syntactically correct (we are using the non-XML 
<a href="http://en.wikipedia.org/wiki/Property_list">Property List Format</a> to
describe the configuration). The pop-up button located on the top-left corner 
indicates the selected configuration (the user can have multiple graph
configurations). The bottom-left text field contains the name of the current
configuration (updates on this field must be followed by typing enter on the
keyboard to take into account the name change). The bottom-right <em>Apply</em>
button activates the current configuration, resulting on an update on the graph
drawings.
<center>
\htmlonly
<a href="triva-graph_configuration.png" border=0><img src="triva-graph_configuration.png" width="50%" border=0></a>
\endhtmlonly
</center>
<b>Basic SimGrid Configuration</b>: The figure shows in the big textfield the
basic configuration that should be used during the analysis of a SimGrid trace
file. The basic logic of the configuration is as follows:
\verbatim
{
  node = (HOST);
  edge = (LINK);
\endverbatim
The nodes of the graph will be created based on the <i>node</i> parameter, which
in this case is the different <em>"HOST"</em>s of the platform 
used to simulate. The <i>edge</i> parameter indicates that the edges of the
graph will be created based on the <em>"LINK"</em>s of the platform. After the
definition of these two parameters, the configuration must detail how
<em>HOST</em>s and <em>LINK</em>s should be drawn. For that, the configuration
must have an entry for each of the types used. For <em>HOST</em>, as basic
configuration, we have:
\verbatim
  HOST = {
    size = power;
    scale = global;
  };
\endverbatim
The parameter <em>size</em> indicates which variable from the trace file will be
used to define the size of the node HOST in the visualization. If the simulation
was executed with availability traces, the size of the nodes will be changed
according to these traces. The parameter <em>scale</em> indicates if the value
of the variable is <em>global</em> or <em>local</em>. If it is global, the value
will be relative to the power of all other hosts, if it is local, the value will
be relative locally.
For <em>LINK</em> we have:
\verbatim
  LINK = {
    src = source;
    dst = destination;
    
    size = bandwidth;
    scale = global;
  };
\endverbatim
For the types specified in the <em>edge</em> parameter (such as <em>LINK</em>),
the configuration must contain two additional parameters: <em>src</em> and
<em>dst</em> that are used to properly identify which nodes this edge is
connecting. The values <em>source</em> and <em>destination</em> are always present
in the SimGrid trace file and should not be changed in the configuration. The
parameter <em>size</em> for the LINK, in this case, is configured as the
variable <em>bandwidth</em>, with a <em>global</em> scale. The scale meaning
here is exactly the same used for nodes. The last parameter is the GraphViz
algorithm used to calculate the position of the nodes in the graph
representation.
\verbatim
  graphviz-algorithm = neato;
}
\endverbatim
<b>Customizing the Graph Representation</b>: triva is capable to handle
a customized graph representation based on the variables present in the trace
file. In the case of SimGrid, every time a category is created for tasks, two
variables in the trace file are defined: one to indicate node utilization (how
much power was used by that task category), and another to indicate link
utilization (how much bandwidth was used by that category). For instance, if the
user declares a category named <i>request</i>, there will be variables named
<b>p</b><i>request</i> and a <b>b</b><i>request</i> (<b>p</b> for power and
<b>b</b> for bandwidth). It is important to notice that the variable
<i>prequest</i> in this case is only available for HOST, and
<i>brequest</i> is only available for LINK. <b>Example</b>: suppose there are
two categories for tasks: request and compute. To create a customized graph
representation with a proportional separation of host and link utilization, use
as configuration for HOST and LINK this:
\verbatim
  HOST = {
    size = power;
    scale = global;
  
    sep_host = {
      type = separation;
      size = power;
      values = (prequest, pcomputation);
    };
  };

  LINK = {
    src = source;
    dst = destination;
    size = bandwidth;
    scale = global;

    sep_link = {
      type = separation;
      size = bandwidth;
      values = (brequest, bcomputation);
    };
  };
\endverbatim
Where <i>sep_host</i> contains a composition of type <i>separation</i> where
its max size is the <i>power</i> of the host and the variables <i>prequest</i>
and <i>pcomputation</i> are drawn proportionally to the size of the HOST. And
<i>sep_link</i> is also a separation where max is defined as the
<i>bandwidth</i> of the link, and the variables <i>brequest</i> and
<i>bcomputation</i> are drawn proportionally within a LINK.
<i>This configuration enables the analysis of resource utilization by MSG tasks,
and the identification of load-balancing issues, network bottlenecks, for
instance.</i> \n
<b>Other compositions</b>: besides <i>separation</i>, it is possible to use
other types of compositions, such as gradients, and colors, like this:
\verbatim
    gra_host = {
      type = gradient;
      scale = global;
      values = (numberOfTasks);
    };
    color_host = {
      type = color;
      values = (is_server);
    };
\endverbatim
Where <i>gra_host</i> creates a gradient within a node of the graph, using a
global scale and using as value a variable called <i>numberOfTasks</i>, that
could be declared by the user using the optional tracing functions of SimGrid.
If scale is global, the max and min value for the gradient will be equal to the
max and min numberOfTasks among all hosts, and if scale is local, the max and
min value based on the value of numberOfTasks locally in each host.
And <i>color_host</i> composition draws a square based on a positive value of
the variable <i>is_server</i>, that could also be defined by the user using the
SimGrid tracing functions. \n
<b>The Graph Visualization</b>: The next figure shows a graph visualization of a
given time-slice of the masterslave_forwarder example (present in the SimGrid
sources). The red color indicates tasks from the <i>compute</i> category. This
visualization was generated with the following configuration:
\verbatim
{
  node = (HOST);
  edge = (LINK);

  HOST = {
    size = power;
    scale = global;
  
    sep_host = {
      type = separation;
      size = power;
      values = (pcompute, pfinalize);
    };
  };
  LINK = {
    src = source;
    dst = destination;
    size = bandwidth;
    scale = global;

    sep_link = {
      type = separation;
      size = bandwidth;
      values = (bcompute, bfinalize);
    };
  };
  graphviz-algorithm = neato;
}
\endverbatim
<center>
\htmlonly
<a href="triva-graph_visualization.png" border=0><img src="triva-graph_visualization.png" width="50%" border=0></a>
\endhtmlonly
</center>

- <b>Understading Triva - colors</b>: An important issue when using Triva is how
  to define colors. To do that, we have to know which variables are defined in
the trace file generated by the SimGrid library. The parameter <em>--list</em> 
lists the variables for a given trace file:
\verbatim
$ Triva -l masterslave_forwarder.trace
iFile
c  platform
c    HOST
v     power
v     is_slave
v     is_master
v     task_creation
v     task_computation
v     pcompute
v     pfinalize
c    LINK
v     bandwidth
v     latency
v     bcompute
v     bfinalize
c  user_type
\endverbatim
We can see that HOST has seven variables (from power to pfinalize) and LINK has
four (from bandwidth to bfinalize). To define a red color for the
<i>pcompute</i> and <i>bcompute</i> (which are defined based on user category
<i>compute</i>), execute:
\verbatim
$ defaults write Triva 'pcompute Color' '1 0 0'
$ defaults write Triva 'bcompute Color' '1 0 0'
\endverbatim
Where the three numbers in each line are the RGB color with values from 0 to 1.

\section options_modelchecking Model-Checking
\subsection options_modelchecking_howto How to use it
To enable the experimental SimGrid model-checking support the program should
be executed with the command line argument 
\verbatim
--cfg=model-check:1 
\endverbatim
Properties are expressed as assertions using the function
\verbatim
void MC_assert(int prop);
\endverbatim

*/