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<p><b><font color="#FF0000">Note</font></b>: actually, there are 2 distinct
classes that compute and give access to statistics: <b><tt><font color="#3366FF">eoStat</font></tt></b>and
<b><tt><font color="#3366FF">eoSortedStat</font></tt></b>.
As its name indicate, the latter is used whenever computing the statistics
require a sorted population: not only this avoids to sort the population
many times, but also it avoids changing the order of the population at
all as <b><tt><font color="#3366FF">eoSortedStat</font></tt></b> objects
work on a temporary vector of fitnesses . But <font color="#FF6600">as
far as their usage is concerned, its makes no difference</font>.
<br>
<hr WIDTH="50%">
<br><a NAME="monitor"></a><b><font color="#000099">eoCheckpoint: </font><font color="#FF0000">Monitoring
eoParameters</font></b>
<br><font color="#000000">The </font><b><tt><font color="#3366FF">eoMonitor</font></tt></b><font color="#000000">
objects are used to display or store to a file a set of </font><b><tt><font color="#3366FF">eoValueParam</font></tt></b><font color="#000000">
objects.</font>
<p><b><font color="#000099">Monitors</font></b>: <b><font color="#FF0000">Available
instances</font></b>
<br>A few monitors are available in the EO distribution:
<ul>
<li>
<b><tt><font color="#3366FF">eoStdoutMonitor</font></tt></b> displays its
parameters in <font color="#FF6600">text format on the screen</font>. The
(optional) boolean value in the constructor modifies the output: when true
(the default), verbose output is used, with one line per parameter. When
false, parsimonious output displays one line for all parameters.</li>

<li>
<b><tt><font color="#3366FF">eoFileMonitor</font></tt></b> writes its parameters
in <font color="#FF6600">text format in a file</font>. A file name is required
in the constructor, and an optional separator character can be added (default
is ' '). Note that the file is by default overwritten by next call to the
same program, unless you pass "true" as third (optional) boolean parameter,
which will result in appending to the file if it ever exists.</li>

<li>
<b><tt><font color="#3366FF">eoGnuplot1DMonitor</font></tt></b> displays
its parameters in <font color="#FF6600">graphical format on the screen</font>
by calling the <b><tt><font color="#660000">gnuplot</font></tt></b> program,
and as of today, only works in the Unix version of EO (as always, volunteers
are welcome to port that to MS Windows). It takes an optional filename
as input, as communication of data with <b><tt><font color="#660000">gnuplot</font></tt></b>
is done through a file. If no filename is provided, the file will be erased
at the end of the run, while it is otherwise kept (though it will be overwritten
by next call to the same program).</li>
</ul>

<p><br><b><font color="#000099">Monitors</font></b>: <b><font color="#FF0000">Adding
to the checkpoint</font></b>
<br>To display something while the algorithm is running, you need to <a href="SecondBitEA.html#monitor_declare">declare</a>
an <b><tt><font color="#3366FF">eoMonitor</font></tt></b> object, <a href="SecondBitEA.html#monitor_add">add</a>
some objects (that must be <b><tt><font color="#3366FF">eoValueParam</font></tt></b>
objects) to that monitor, and of course <a href="SecondBitEA.html#monitor_pass">add</a>
the monitor to the <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b>
you use in the algorithm.
<br>
<hr WIDTH="50%">
<br><a NAME="update"></a><b><font color="#000099">eoCheckpoint: Updating
things</font></b>
<br><font color="#000000">The last type of objects that&nbsp; </font><b><tt><font color="#3366FF">eoCheckpoint</font></tt></b><font color="#000000">
can handle are </font><b><tt><font color="#3366FF">eoUpdater</font></tt></b><font color="#000000">
objects. You should simply encapsulate in an </font><b><tt><font color="#3366FF">eoUpdater</font></tt></b><font color="#000000">
anything you wish to do which does not fit into one of the above category.
Note that their </font><b><tt><font color="#660000">operator() method</font></tt></b><font color="#000000">
does not receive any argument.</font>
<p><b><font color="#000099">Updater: </font><font color="#FF0000">Available
instances</font></b>: A few updaters are available in the EO distribution:
<ul>
<li>
<b><tt><font color="#3366FF">eoIncrementor</font></tt></b> A simple updater
which maintains a <font color="#FF6600">counter</font> (an <b><tt><font color="#3366FF">eoValueParam</font></tt></b>
that needs to be created beforehand, and passed in the constructor). It
is incremented every time the <b><tt><font color="#660000">operator()</font></tt></b>
method is called (every generation at the moment). You can of course also
give an increment in the constructor (1 by default).</li>

<li>
<a NAME="statesaver"></a><b><tt><font color="#3366FF">eoCountedStateSaver</font></tt></b>
and <b><tt><font color="#3366FF">eoTimedStateSaver</font></tt></b> can
be used to <font color="#FF6600">save</font> some existing <b><tt><font color="#3366FF">eoState</font></tt></b>
(see <a href="#state">above</a>) to a file regularly, either based on the
generation count (e.g. every 4 generations) or based on the clock (e.g.
every 5 seconds).</li>
</ul>
<b><font color="#000099">Updater: </font><font color="#FF0000">Adding to
the checkpoint</font></b>
<br>A very simple example of using an <b><tt><font color="#3366FF">eoUpdater</font></tt></b>
is given in the code for SecondBitEA: First <a href="SecondBitEA.html#param_declare">declare</a>
an <b><tt><font color="#3366FF">eoValueParam</font></tt></b> object, then
<a href="SecondBitEA.html#param_pass">use
it to construct</a> an <b><tt><font color="#3366FF">eoIncrementor</font></tt></b>
that you must <a href="SecondBitEA.html#updater_pass">add</a> to the <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b>
in order to activate its update. You can then use the parameter for your
purpose, for instance as a first coordinate for a monitor.
<br>Note also how to use the statesavers: first <a href="SecondBitEA.html#outstate_declare">declare</a>
a state, then <a href="SecondBitEA.html#outstate_register">register</a>
whatever you think necessary to that state, then <a href="SecondBitEA.html#statesaver_declare">pass</a>
the state to some state-saver - and don't forget to <a href="SecondBitEA.html#statesaver_pass">add</a>
the statesavers to the current <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b>.
<br>
<hr WIDTH="100%">
<br><b><font color="#000099"><font size=+2>Exercise 1:</font></font></b>
<ul>
<li>
<font color="#000000">The code of </font><b><tt><font color="#660000"><font size=+1>SecondBitEA</font></font></tt></b><font color="#000000">
display things in the current window in text format. Replace the </font><b><tt><font color="#3366FF">eoFileMonitor</font></tt></b><font color="#000000">
by an </font><b><tt><font color="#3366FF">eoGnuplot1DMonitor</font></tt></b><font color="#000000">
and watch the </font><b><font color="#FF6600">graphical output </font></b><font color="#000000">(</font><font color="#FF6600">Unix</font><font color="#000000">
systems with </font><font color="#FF6600">gnuplot</font><font color="#000000">
installed only, sorry).</font></li>

<li>
<font color="#000000">Note that you must also replace the </font><b><tt><font color="#3366FF">eoSecondMomentStat</font></tt></b><font color="#000000">
by an </font><b><tt><font color="#3366FF">eoAverageStat</font></tt></b><font color="#000000">,
otherwise the standard deviations won't make any sense here.</font></li>

<li>
<font color="#000000">Please try to understand why the average is always
0 before taking a look at the solution (file <a href="NoWay.html">exercise1.cpp</a>).</font></li>

<li>
<font color="#000000">Then run</font></li>

<br><b><tt><font color="#660000">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
exercise1 --vecSize=1000 --maxGen=1000</font></tt></b>
<br><font color="#000000">to get a chance to see something happening before
the program ends!</font></ul>

<hr WIDTH="100%"><b><font color="#000099"><font size=+2>Exercise 2:</font></font></b>
<br><font color="#000000">Write the </font><b><tt><font color="#3366FF">eoDiversityStat</font></tt></b><font color="#000000">
stat computation and test it. Thanks to send us the code!</font>
<br>
<hr WIDTH="100%">
<br><b><font color="#000099"><font size=+2>Exercise 3:</font></font></b>
<br><font color="#000000">Write the code for an </font><b><tt><font color="#3366FF">eoGnuplotSecondStatMonitor</font></tt></b><font color="#000000">
that would display the </font><b><tt><font color="#3366FF">eoSecondMomentStat</font></tt></b><font color="#000000">
(i.e. take into account the standard deviations and display them as error-bars.</font>
<br><font color="#000000">Again, send us the code afterwards, thanks :-)</font>
<br>
<hr WIDTH="100%">
<br><b><font color="#000099"><font size=+2>Lessons learned:</font></font></b>
<ul>
<li>
Value of program parameters can be set <b><font color="#FF6600">at run-time</font></b>
using the <b><tt><font color="#3366FF">eoParser</font></tt></b> class.</li>

<li>
<b><font color="#FF6600">Snapshots</font></b> of the algorithms can easily
be <font color="#FF6600">saved</font> (and <font color="#FF6600">restored</font>)
thanks to the <b><tt><font color="#3366FF">eoState</font></tt></b> class.</li>

<li>
The <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b> mechanism
let you <b><font color="#FF6600">do things every generation</font></b>
without modifying existing algorithms, by simply writing the necessary
code and encapsulating it into an object that <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b>
is aware of, that are at the moment the following:</li>

<li>
computing <b><font color="#FF6600">statistics</font></b>, <b><font color="#FF6600">displaying
</font></b>parameters
(e.g. statistics),&nbsp; <b><font color="#FF6600">saving</font></b> the
<b><tt><font color="#3366FF">(eo)State</font></tt></b>
of the program.</li>
</ul>
In next lesson you will find out that many <a href="intro.html#adaptive">adaptive
techniques</a> (the state-of-the-art in Evolutionary Computation) can easily
be programmed through the <b><tt><font color="#3366FF">eoUpdater</font></tt></b>
construct.
<br>
<hr WIDTH="100%"><a href="eoLesson2.html">Lesson 2</a> -
<a href="eoLesson4.html">Lesson
4</a> -
<a href="eoTutorial.html">Main page</a> -
<a href="eoTopDown.html">Algorithm-Based</a>
- <a href="eoBottomUp.html">Component-Based</a> - <a href="eoProgramming.html">Hints</a>
-<b> <font face="Arial,Helvetica"><font size=+1><a href="../../doc/html/index.html">EO
documentation</a></font></font></b>
<br>
<hr>
<address>
<a href="mailto:[e-mail]">Marc Schoenauer</a></address>

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