46d9671e05
tutorial/html dir to doc/ dir: it's simpler, and I was not able to do the same thing in Windows anyway!
256 lines
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256 lines
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<meta name="GENERATOR" content="Mozilla/4.75 [en] (X11; U; Linux 2.2.17-21mdksmp i686) [Netscape]">
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<title>EO Programming guide</title>
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</head>
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<body text="#000000" link="#0000EE" vlink="#551A8B" alink="#FF0000" background="beige009.jpg">
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<a href="eoTutorial.html">Tutorial main page </a>-
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<a href="eoTopDown.html">Top-Down
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page</a> - <a href="eoBottomUp.html">Bottom-up page</a> - <a href="eoProgramming.html">Programming
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hints</a> - <font face="Arial,Helvetica"><a href="../../doc/html/index.html">EO
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documentation</a></font>
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<br>
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<hr WIDTH="100%"><!-- -------------- End of header ------------------ --><!-- ----------------------------------------------- -->
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<center>
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<h1>
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<font color="#FF0000">EO Programming guide</font></h1></center>
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<!-- ----------------------------------------------- --><a href="#templates">Templates</a>,
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<a href="#functors">Functors</a>,
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<a href="#STL">STL
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Library</a>, random numbers, <a href="#notations">EO programming style</a>!
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<br>
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<hr WIDTH="100%">
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<br><a NAME="templates"></a><b><font color="#000099"><font size=+1>Templates</font></font></b>
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<br>Most EO code is written using templates. This allows to write generic
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code, i.e. involving a class which doesn't have to be known when writing
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the code -- but only when compiling it. In some sense this is similar to
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naming variables in algebra: you can write a lot of equations involving
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some variable $x$ without knowing even it if will be an integer or a float
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(or a matrix or ...). The main basic type that is templatized in EO is
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the fitness: an EO object is some object which has a fitness of some type
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F that can be anything. The definition for that is (see<font face="Arial,Helvetica"><a href="doc/EO.h-source.html">EO.h</a></font>)
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<p><b><tt><font color="#999900"><font size=+1>template<F> class EO</font></font></tt></b>
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<p>The idea is that, later in your code, you can declare for instance as
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in <a href="FirstBitGA.html#representation">FirstBitGA.cpp</a>
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<p><b><tt><font color="#999900"><font size=+1>typedef eoBin<double>
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Genotype;</font></font></tt></b>
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<p>meaning that in that file, you will manipulate as <b><tt><font color="#999900"><font size=+1>Genotype</font></font></tt></b>
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objects that are EO objects <font color="#000000">whose</font><b><font color="#FF6600">fitness</font></b><font color="#000000">
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is a </font><font color="#FF6600"><b>double</b>.</font>
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<p>Whereas the advantages are obvious (writing generic reusable code instead
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of having to rewrite the same pieces of code for different types), there
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are some drawbacks: namely, it makes some of the compiler error messages
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hard to understand; and it forbids the compilation of most parts of EO
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into an object library file, as the actual types are not known in advance.
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<p>
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<hr WIDTH="100%">
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<br><a NAME="functors"></a><b><font color="#000099"><font size=+1>Functors</font></font></b>
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<p>Though EO is a library, it contains almost no functions!
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<br>EO only contains functors, that are objects which have a method called
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<b><tt><font color="#FF6600"><font size=+1>operator()</font></font></tt></b>.
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Such objects are used as if they were a function, but the big differences
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are that
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<ul>
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<li>
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functors are functions with private data</li>
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<li>
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you can have different functors objects of the same class, i.e. you can
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use the same functionality with different parameters</li>
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<li>
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you can heave a hierarchy of functors objects, which means that you have
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a hierarchy of functions with defaults behaviors and specialized sub-functions</li>
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<li>
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...</li>
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</ul>
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Functors are so intimately linked to EO that a base class (<a href="../../doc/html/class_eofunctorbase.html">eoFunctorBase</a>)
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has been designed to hold all functors. This base class is itself divided
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into three derived class. These classes tell you immediately what kind
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of arguments the <font color="#993300">operator()</font> method requires
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and what kind of result it produces. See <a href="#notations">EO conventions</a>,
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and
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the <a href="doc/class_eofunctorbase.html">inheritance diagram of class
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eoFunctorBase</a>.
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<p><b><font color="#000099">Example</font></b>
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<p>A good example is given by the <tt><font color="#990000"><font size=+1>eoEvalFuncPtr</font></font></tt>
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class
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<p><tt><font color="#993300">class MyClass</font></tt>
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<br><tt><font color="#993300">{ ...</font></tt>
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<br><tt><font color="#993300"> void operator()(ArgType
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arg)</font></tt>
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<br><tt><font color="#993300"> {</font></tt>
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<br><tt><font color="#993300">
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// do what you have to do</font></tt>
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<br><tt><font color="#993300"> }</font></tt>
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<br><tt><font color="#993300">}; // end of class declaration</font></tt>
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<p>is used later in the code in something like
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<br>
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<p><tt><font color="#993300">ArgType myArgument;</font></tt>
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<br><tt><font color="#993300">MyClass myObject; // myObject
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is an object of class MyClass ...</font></tt>
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<br><tt><font color="#993300">myObject(myArgument); // calls method
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operator() of object myObject with argument myArgument ...</font></tt>
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<br>
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<br>
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<br>
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<h2>
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Why not plain C functions?</h2>
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Consider for instance variation operators. Of course, we could declare
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them as function acting on some objects.
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<p><tt>Blabla</tt>
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<p>
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<hr WIDTH="100%">
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<br><a NAME="STL"></a><b><font color="#000099"><font size=+1>A very brief
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introduction to STL</font></font></b>
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<p>All EO heavily relies on <b><font color="#FF6600">STL, the Standard
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Template Library</font></b>.
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<br>But <font color="#FF6600">you don't have to know more than a few words
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of STL</font> to use EO (like with "hello", "please" and "goodbye" you
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can survive in a foreign country :-) and even to contribute to new EO features.
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<p>You will only find here the basics of STL that you will need to understand
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most of EO code - and to guess what the parts you don't understand are
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actually doing. Don't worry, <b><font color="#FF6600">I </font></b>don't
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understand everything :-)
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<p>STL provides the user with <b><font color="#FF6600">container</font></b>
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and <b><font color="#FF6600">algorithms</font></b>. And you can apply (almost)
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all algorithms on (almost) all containers.
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<p><b><font color="#000099">Containers</font></b>
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<br>Containers are high level data types used to hold simpler data - the
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most widely used example of a container is the <b><font color="#FF6600">vector</font></b>
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construct.
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<br>The use of STL containers relieve the user from memory management.
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<ul>
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<li>
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<b><tt><font color="#000099"><font size=+1>vector </font></font></tt></b><font color="#000000">The
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most widely used container is a one-dimensional array of items.</font></li>
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<br><font color="#000000">Data manipulation: suppose </font><font color="#FF6600">v
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is an STL </font><tt><font color="#993300"><font size=+1>vector<AtomType></font></font></tt><font color="#000000">.
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Then</font>
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<br><tt><font color="#993300"><font size=+1>v[i]</font></font></tt><font color="#000000">
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is the ith element of v, as in standard C arrays</font>
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<br><tt><font color="#993300"><font size=+1>v.size()</font></font></tt><font color="#000000">
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is the number of elements of v</font>
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<br><tt><font color="#993300"><font size=+1>v.push_back(atom)</font></font></tt><font color="#000000">
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appends the </font><tt><font color="#993300"><font size=+1>atom</font></font></tt><font color="#000000">
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at end of </font><tt><font color="#993300"><font size=+1>v</font></font></tt><font color="#000000">,
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provided of course that </font><tt><font color="#993300"><font size=+1>atom</font></font></tt><font color="#000000">
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is of type </font><tt><font color="#993300"><font size=+1>AtomType</font></font></tt>
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<br><font color="#000000">blabla</font>
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<li>
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<b><tt><font color="#000099"><font size=+1>pair</font></font></tt></b></li>
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<br><font color="#000000">This simple container allows you to hold two
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data types together. It is very handy for temporary data handling. Assuming
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p is a </font><tt><font color="#993300"><font size=+1>pair<AtomType1,
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AtomType2></font></font></tt><font color="#000000">,</font>
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<br><tt><font color="#993300"><font size=+1>p.first()</font></font></tt><font color="#000000">
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and </font><tt><font color="#993300"><font size=+1>p.second()</font></font></tt><font color="#000000">
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refer to the encapsulated data, of respective types </font><tt><font color="#993300"><font size=+1>AtomType1</font></font></tt><font color="#000000">and
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</font><tt><font color="#993300"><font size=+1>AtomType2.</font></font></tt>
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<li>
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<b><tt><font color="#000099"><font size=+1>Blabla</font></font></tt></b></li>
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</ul>
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There are many other types of containers that are not used in EO and that
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we will not present here.
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<p><b><font color="#000099">STL Algorithms</font></b>
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<br>Algorithms are functions acting on containers - the most widely used
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example of a STL algorithm is the <b><font color="#FF6600">sort</font></b>
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function.
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<br>Blabla
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<p><b><font color="#000099">Drawbacks</font></b>
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<br>The main drawback I see in using STL is that it makes it almost
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<b><font color="#FF6600">impossible
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to use a debugger </font></b>normally: whereas access to data is made simple
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to the programmer, data structures are actually so complex, and debuggers
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so willing to display everything that you get lines of template instantiation
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when asking your debugger what is inside some container! For instance I
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could never visualize some
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<tt><font color="#FF6600"><font size=+1>v[i]</font></font></tt>
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with <tt><font color="#FF6600"><font size=+1>gbd</font></font></tt>, v
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being an STL vector!
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<br>But there nonetheless are so many advantages !!!
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<p>
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<hr WIDTH="100%">
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<br><a NAME="random"></a><b><font color="#000099"><font size=+1>Random
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numbers</font></font></b>
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<br>Evolutionary Algorithms make intensive use of random numbers. Random
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numbers are simulated in computers by using <font color="#FF6600">pseudo-random</font>
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number generators (RNGs for short), i.e. functions that return series of
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numbers who look random (w.r.t. some statistical criteria).
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<p>To make sure the random number generator is as good as possible, and
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to ensure reproducibility of the results across different platforms, EO
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has its own RNG, the ``<font color="#FF6600">Mersenne Twister</font>''
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random number generator MT19937 (thanks to <font color="#FF0000">Takuji
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Nishimura</font>, see <font face="Arial,Helvetica"><font size=+1><a href="../../../../doc/html/class_eorng.html">eoRNG.h</a></font></font>
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comments).
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<p>Though you can define and use as many RNGs as you wish in EO, the library
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also provides you with a global RNG termed rng: using only that single
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RNG in all calls to random numbers allows one to be able to <b><font color="#FF6600">reproduce
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a given run</font></b>:
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<ul>
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<li>
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as strange it seems for a random algorithm, it is mandatory for debugging
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purposes</li>
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<li>
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random numbers are computed starting from a seed - starting from the same
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seed will lead to the same series of pseudo-random numbers, and hence to
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the same results of the algorithms. All examples in this tutorial will
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use the RNG seeding procedure, see e.g. in <a href="FirstBitGA.html#random">Lesson1</a>.</li>
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<li>
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to simulate "true" random runs, you can just seed the RNG with a machine-clock
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related number, e.g. calling time(0), as done for instance in <a href="SecondBitEA.html#random">Lesson3</a>
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(and after).</li>
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</ul>
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As RNGs only produce (by definition) numbers that are uniformly distributed
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integers between 0 and some maximal number, EO provides you with random
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numbers following <b><font color="#FF6600">different probability distribution</font></b>
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(e.g. floating point following <font face="Arial,Helvetica"><font size=+1><a href="../../../../doc/html/class_eorng.html#a8">normal
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distribution</a></font></font>).
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<p>EO also provides <a href="../../../../doc/html/rnd_generators.h-source.html">random_generators</a>
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that can be used in STL call to generate series of random numbers, as in
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<a href="eoInit.html">eoPop
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initializers</a>.
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<p>
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<hr WIDTH="100%">
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<br><a NAME="notations"></a><b><font color="#000099"><font size=+1>EO conventions
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and naming style</font></font></b>
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<br>A few naming conventions should help you to navigate more easily through
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EO:
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<ul>
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<li>
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The name of local variables should start with a lower case letter</li>
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<li>
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The name of the parameters to a function should start with an underscore
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(_)</li>
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<br>The initialization parameters of constructors, for instance,
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should be named from the names of the variables they are used to initialize.
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<li>
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The names of classes should start with eo + an Uppercase letter</li>
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<li>
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Blabla</li>
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</ul>
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<hr WIDTH="100%">
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<br><a href="eoTutorial.html">Tutorial main page </a>- <a href="eoTopDown.html">Top-Down
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page</a> - <a href="eoBottomUp.html">Bottom-up page</a> - <a href="eoProgramming.html">Programming
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hints</a> - <font face="Arial,Helvetica"><a href="../../doc/html/index.html">EO
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documentation</a></font>
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<br>
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<hr>
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<address>
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<a href="mailto:Marc.Schoenauer@polytechnique.fr">Marc Schoenauer</a></address>
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<br><!-- Created: Mon Oct 30 19:04:58 CET 2000 --><!-- hhmts start -->Last
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modified: Mon Nov 6 07:01:57 CET 2000<!-- hhmts end -->
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</body>
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</html>
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