eolesson3.html

这是linux下的进化计算的源代码。 === === === === === === === === === === === ===== check latest news at http:

<br>and see the algorithm run as before (OneMax optimized on 8-bits bitstrings).
But you can now type in
<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

<b><tt><font color="#FF6666">SecondBitEA --vecSize=100</font></tt></b>
<br>and see the output of the optimization of OneMax on 100-bit bitstrings.
<br>&nbsp;
<li>
Take a look at all available parameters by typing in</li>

<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

<b><tt><font color="#FF6666">SecondBitEA --help</font></tt></b>
<br>or by going into the code: all parameter inputs have been grouped in
the
<a href="SecondBitEA.html#parametres">read_param</a> function.
<br>&nbsp;
<li>
After running the algorithm, a new file has been created, named <b><tt><font color="#990000">SecondBitEA.status</font></tt></b>:
it contains the list of all actual parameters used, and can directly be
used as parameter input file: change the file name (e.g. to <b><tt><font color="#660000">SecondBitEA.param</font></tt></b>),
edit it, change whichever parameter you want, and type in</li>

<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<b><tt><font color="#FF6666">SecondBitEA @SecondBitEA.param</font></tt></b>
<br>and you will see all values that you defined into the file taken into
account.
<br>&nbsp;
<li>
The <font color="#FF6600">priority</font> remains to the <font color="#FF6600">command-line</font>,
so you can still override the values in the parameter file by giving a
new value directly on the command-line.</li>
</ul>

<hr WIDTH="50%"><a NAME="parameters"></a><b><font color="#000099">eoParser:</font><font color="#FF0000">
Programming parameter input:</font></b>
<br>The code of SeconBitEA provides examples of parameters reading. Lets
take the example of the <a href="eoProgramming.html#random">random number
generator </a><b><tt><font color="#660000">seed</font></tt></b>.&nbsp;
Of course, you first need to <a href="SecondBitEA.html#parser_declare">declare
an eoParser object</a> (it needs the standard argc and argv in its constructor).
<ul>
<li>
You must first <a href="SecondBitEA.html#random">declare a parameter</a>
of type <b><tt><font color="#660000">uint32</font></tt></b> (32-bits integer).
The arguments are: default value, long keyword, comment (that will appear
in the help message and in the output "status" file if any) and optional
character keyword.</li>

<li>
Then you must <a href="SecondBitEA.html#seed_process">pass it to the parser</a>
using the processParam method. The optional argument is a section name,
that will be used to make the output of the parser look clean and ordered.</li>

<li>
Finally, you need to <a href="SecondBitEA.html#seed_assign">assign the
value</a> to the variable <b><tt><font color="#660000">seed</font></tt></b>.
Note that the <b><tt><font color="#990000">value()</font></tt></b> method
of eoParam returns a reference, so you can eventually modify its value
somewhere else later (though of course this is not any useful for variable
<b><tt><font color="#660000">seed</font></tt></b>!).</li>
</ul>
There is however another way to achieve the same result in less lines of
code - with a different memory management. This is what is done in the
code for eoRealEA. The same parameter for the <a href="eoProgramming.html#random">random
number generator </a><b><tt><font color="#660000">seed</font></tt></b>
is read, but in <a href="SecondRealEA.html#random">one single line of code</a>.&nbsp;
The only difference is that now you cannot access the eoValueParam object
itself - but this is not often necessary.
<br>Be careful to ensure that the type of the default value in the call
to <a href="../../doc/html/classeo_parameter_loader.html#a3">eoParameterLoader::createParam</a>
method as this is the only way the compiler can desambiguate the template
(remember that eoParameterLoader is <font color="#000000"><a href="../../doc/html/classeo_parser.html">a
base class for eoParser</a></font>.
<br>
<hr WIDTH="100%">
<br><a NAME="state"></a><b><font color="#000099"><font size=+2>eoState:
saving and loading</font></font></b><font color="#000000">You might have
noticed in the&nbsp; </font><b><tt><font color="#660000">read_param</font></tt></b><font color="#000000">
described above a </font><font color="#FF6600">new parameter</font><font color="#000000">
named </font><b><tt><font color="#660000"><a href="SecondBitEA.html#_load_name">load_name.</a></font></tt></b><font color="#000000">
Now if you go to the <a href="SecondBitEA.html#init">init section</a> of
the code, you will see an alternative way of </font><font color="#CC33CC">initializing
the population</font><font color="#000000">: if load_name is an empty string,
then we do as in the preceding example and use an eoInitFixedLength object.
However, if a load_name name was entered, the population is read through
the </font><b><tt><font color="#660000"><a href="SecondBitEA.html#instate.load">inState.load(load_name)</a></font></tt></b><font color="#000000">
instruction. Moreover, the comment says "Loading pop </font><font color="#FF6600">and
rng</font><font color="#000000">".</font>
<p><font color="#000000">This is made possible using the </font><b><tt><font color="#3366FF">eoState</font></tt></b><font color="#000000">
class. </font><b><tt><font color="#3366FF">eoState</font></tt></b><font color="#000000">
objects maintain references to </font><b><tt><font color="#660000">eoObjects</font></tt></b><font color="#000000">
that have both an input method (</font><b><tt><font color="#3366FF">readFrom</font></tt></b><font color="#000000">)
and an output method (</font><b><tt><font color="#3366FF">printOn</font></tt></b><font color="#000000">),
i.e. that derive from the base class </font><b><font face="Arial,Helvetica"><font color="#660000"><font size=+1><a href="../../doc/html/classeo_persistent.html">eoPersistent</a></font></font></font></b><font color="#000000">.
You must first </font><b><tt><font color="#3366FF"><a href="SecondBitEA.html#register">register</a></font></tt></b><font color="#000000">
object into a state, and can then save them to a (text) file, and later
read them from that file using the </font><b><tt><font color="#3366FF">load</font></tt></b><font color="#000000">
method, as done <a href="SecondBitEA.html#loadstate">here</a>.</font>
<br><font color="#000000">Of course, you can call the </font><b><tt><font color="#3366FF">save</font></tt></b><font color="#000000">
method for an </font><b><tt><font color="#3366FF">eoState</font></tt></b><font color="#000000">
object anywhere in the code. But the <a href="#statesaver">checkpointing</a>
mechanism offers you better ways to do that - and it's so easy ....</font>
<p>Note that an eoState alos has another use in EO whan it comes to memory
management: it can be a repository of pointers that are not allocated within
obects - allowing to delete them by simply deleting the eoState (see <a href="eoLesson4.html#memory">Lesson
4)</a>.
<br>
<hr WIDTH="100%"><a NAME="checkpoint"></a><b><font color="#000099"><font size=+2>eoCheckpoint:
every generation I'd like to ...</font></font></b>
<br><font color="#000000">The checkpointing mechanism is a very powerful
construct to perform some </font><b><font color="#FF6600">systematic actions</font></b><font color="#000000">
every generation - like </font><font color="#FF6600">saving things</font><font color="#000000">
(using eoState objects described above), computing </font><font color="#FF6600">statistics</font><font color="#000000">
on the population, </font><font color="#FF6600">updating</font><font color="#000000">
dynamical parameters or </font><font color="#FF6600">displaying</font><font color="#000000">
information.</font>
<p><b><tt><font color="#3366FF">eoCheckpoint</font></tt></b><font color="#000000">
objects are </font><b><tt><font color="#3366FF">eoContinue</font></tt></b><font color="#000000">
objects that contain </font><font color="#FF6600">pointers to different
types</font><font color="#000000"> of objects. When their </font><b><tt><font color="#660000">operator()</font></tt></b><font color="#000000">
method is called (i.e. every generation in the examples up to now), they
first call the </font><b><tt><font color="#660000">operator()</font></tt></b><font color="#000000">
methods of all object they contain, and then return their result as an
</font><b><tt><font color="#3366FF">eoContinue</font></tt></b><font color="#000000">
object (i.e. should we continue or stop).</font>
<br><b><font color="#FF0000">Programming: </font></b><font color="#000000">To
do something every generation, you simply need to </font><b><tt><font color="#3366FF">add</font></tt></b><font color="#000000">
an object whose </font><b><tt><font color="#660000">operator()</font></tt></b><font color="#000000">
does what you want to the eoState that you will use as continuator in the
algorithm.</font>
<br>
<hr WIDTH="50%"><a NAME="stop"></a><b><font color="#000099">eoCheckpoint:
</font><font color="#FF0000">Stopping</font></b>
<br><font color="#000000">The </font><b><tt><font color="#3366FF">eoContinue</font></tt></b><font color="#000000">
part of an </font><b><tt><font color="#3366FF">eoCheckpoint</font></tt></b><font color="#000000">
is a single object, <a href="SecondBitEA.html#checkpoint">passed to the
constructor</a>. If you want more that one stopping criterion, use an <a href="SecondBitEA.html#stop">eoCombinedContinue</a>
object as described in <a href="eoLesson2.html#combinedContinue">Lesson2</a>.</font>
<br>
<hr WIDTH="50%">
<br><a NAME="stats"></a><b><font color="#000099">eoCheckpoint: </font><font color="#FF0000">Computing
statistics</font></b>
<br><font color="#000000">Statistics are computed using </font><b><tt><font color="#3366FF">eoStat</font></tt></b><font color="#000000">
objects, i.e. functor objects whose </font><b><tt><font color="#660000">operator()</font></tt></b><font color="#000000">
receives as argument a reference to a population as argument, and can hence
compute whatever is needed over that population. </font><b><tt><font color="#3366FF">eoStat</font></tt></b><font color="#000000">
objects are </font><font color="#FF6600">templatized</font><font color="#000000">
over the type of what they compute (e.g. </font><b><tt><font color="#660000">double</font></tt></b><font color="#000000">,
or </font><b><tt><font color="#660000">pair&lt;double></font></tt></b><font color="#000000">,
or ...). But looking at the <a href="../../doc/html/classeo_stat.html">inheritance
diagram</a> of the </font><b><tt><font color="#3366FF">eoStat</font></tt></b><font color="#000000">
class, you find that </font><b><tt><font color="#3366FF">eoStat</font></tt></b><font color="#000000">
objects are also </font><b><tt><font color="#3366FF">eoValueParam</font></tt></b><font color="#000000">
objects. And this allows </font><b><tt><font color="#3366FF">eoStat</font></tt></b><font color="#000000">
to be used within </font><b><tt><font color="#3366FF">eoMonitor</font></tt></b><font color="#000000">
object, and hence </font><b><font color="#FF6600">displayed</font></b><font color="#000000">
to the user!</font>
<p><b><font color="#000099">Statistics: </font><font color="#FF0000">Available
instances</font></b>
<br>Some widely used statistics are already available (and of course you
can build you own!).
<ul>
<li>
<b><tt><font color="#3366FF">eoBestFitnessStat</font></tt></b> returns
the fitness value of the best individual in the population (of type <b><tt><font color="#660000">FitnessType</font></tt></b>,
whatever this is).</li>

<li>
<b><tt><font color="#3366FF">eoAverageStat</font></tt></b> and <b><tt><font color="#3366FF">eoSecondMomentStat</font></tt></b>
respectively return the average (type double, assumes that <b><tt><font color="#660000">FitnessType</font></tt></b>
is castable to a double) and a pair made of the average and the standard
deviation (type <b><tt><font color="#660000">pair&lt;double></font></tt></b>)
of the fitnesses in the populations.</li>

<li>
<b><tt><font color="#3366FF">eoDiversityStat</font></tt></b> returns the
diversity in the population: assuming that there is a distance function
defined among individuals, it returns the average inter-individuals distance.
See also Exercise 2.</li>
</ul>
<b><font color="#000099">Statistics: </font><font color="#FF0000">Adding
to the checkpoint</font></b>
<br>To compute more statistics when your algorithm is running, simply <a href="SecondBitEA.html#stat_declare">declare</a>
the corresponding eoStat objects, and <a href="SecondBitEA.html#stat_pass">add</a>
them to the <b><tt><font color="#3366FF">eoCheckpoint</font></tt></b> you
use in the algorithm. But it hardly makes any sense if you don't <b><font color="#3366FF">monitor</font></b>
those statistics (i.e. either displaying them on the screen, or storing
them into a file): see next section!