Replace genetic algorithm ASCII-art with a real figure

Author: Jürgen Purtz
Discussion: https://postgr.es/m/c6027f7a-78ea-8453-0837-09903ba5fd9b@purtz.de

Author: alvherre

doc/src/sgml/geqo.sgml

@@ -84,59 +84,26 @@
     Through simulation of the evolutionary operations <firstterm>recombination</firstterm>,
     <firstterm>mutation</firstterm>, and
     <firstterm>selection</firstterm> new generations of search points are found
-    that show a higher average fitness than their ancestors.
+    that show a higher average fitness than their ancestors. <xref linkend="geqo-figure"/>
+    illustrates these steps.
    </para>
 
+   <figure id="geqo-figure">
+    <title>Structure of a Genetic Algorithm</title>
+    <mediaobject>
+     <imageobject>
+      <imagedata fileref="images/genetic-algorithm.svg" format="SVG" width="100%"/>
+     </imageobject>
+    </mediaobject>
+   </figure>
+
    <para>
     According to the <systemitem class="resource">comp.ai.genetic</systemitem> <acronym>FAQ</acronym> it cannot be stressed too
     strongly that a <acronym>GA</acronym> is not a pure random search for a solution to a
     problem. A <acronym>GA</acronym> uses stochastic processes, but the result is distinctly
     non-random (better than random).
    </para>
 
-   <figure id="geqo-diagram">
-    <title>Structured Diagram of a Genetic Algorithm</title>
-
-    <informaltable frame="none">
-     <tgroup cols="2">
-      <tbody>
-       <row>
-        <entry>P(t)</entry>
-        <entry>generation of ancestors at a time t</entry>
-       </row>
-
-       <row>
-        <entry>P''(t)</entry>
-        <entry>generation of descendants at a time t</entry>
-       </row>
-      </tbody>
-     </tgroup>
-    </informaltable>
-
-<literallayout class="monospaced">
-+=========================================+
-|&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;&gt;  Algorithm GA  &lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;|
-+=========================================+
-| INITIALIZE t := 0                       |
-+=========================================+
-| INITIALIZE P(t)                         |
-+=========================================+
-| evaluate FITNESS of P(t)                |
-+=========================================+
-| while not STOPPING CRITERION do         |
-|   +-------------------------------------+
-|   | P'(t)  := RECOMBINATION{P(t)}       |
-|   +-------------------------------------+
-|   | P''(t) := MUTATION{P'(t)}           |
-|   +-------------------------------------+
-|   | P(t+1) := SELECTION{P''(t) + P(t)}  |
-|   +-------------------------------------+
-|   | evaluate FITNESS of P''(t)          |
-|   +-------------------------------------+
-|   | t := t + 1                          |
-+===+=====================================+
-</literallayout>
-   </figure>
   </sect1>
 
   <sect1 id="geqo-pg-intro">

doc/src/sgml/images/Makefile

@@ -3,6 +3,7 @@
 # see README in this directory about image handling
 
 ALL_IMAGES = \
+	genetic-algorithm.svg \
 	gin.svg \
 	pagelayout.svg
 

doc/src/sgml/images/genetic-algorithm.gv

@@ -0,0 +1,48 @@
+digraph {
+	layout=dot;
+
+	// default values
+	node  [shape=box, label="", fontname="sans-serif", style=filled, fillcolor=white, fontsize=8];
+	graph [fontname="sans-serif"]; // must be specified separately
+	edge  [fontname="sans-serif"]; // must be specified separately
+
+	// an unobtrusive background color
+	pad="1.0, 0.5";
+	bgcolor=whitesmoke;
+
+	// layout of edges and nodes
+	splines=ortho;
+	nodesep=0.3;
+	ranksep=0.3;
+
+	// nodes
+	a1[label="INITIALIZE t := 0"];
+	a2[label="INITIALIZE P(t)"];
+	a3[label="evaluate FITNESS of P(t)"];
+	a4[shape="diamond", label="STOPPING CRITERION"; width=4];
+
+	// connect 'end' node with 'a9' node (bottom of figure)
+	{
+	  rank=same;
+	  a9[label="t := t + 1"];
+	  // end-symbol similar to UML notation
+	  end[shape=doublecircle, label="end", width=0.5];
+	}
+
+	a5[label="P'(t) := RECOMBINATION{P(t)}"];
+	a6[label="P''(t) := MUTATION{P'(t)}"];
+	a7[label="P(t+1) := SELECTION{P''(t) + P(t)}"];
+	a8[label="evaluate FITNESS of P''(t)"];
+
+	// edges
+	a1 -> a2 -> a3 -> a4;
+	a4 -> a5[xlabel="false   ", fontsize=10];
+	a4 -> end[xlabel="true  ",  fontsize=10];
+	a5 -> a6 -> a7 -> a8 -> a9;
+	a4 -> a9 [dir=back];
+
+	// explain the notation
+	expl [shape=plaintext, fontsize=10, width=3.2, fillcolor=whitesmoke,
+	      label="P(t): generation of ancestors at a time t\lP''(t): generation of descendants at a time t\l"];
+
+}