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<HTML> <HEAD> <!--SCRIPT LANGUAGE="JavaScript" SRC="http://a1835.g.akamai.net/f/1835/276/3h/www.netlibrary.com/include/js/dictionary_library.js"></SCRIPT> <SCRIPT LANGUAGE="JavaScript"> if (!opener){document.onkeyup=parent.turnBookPage;} </SCRIPT!--> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache"> <META HTTP-EQUIV="Pragma" CONTENT="no-cache"> <META HTTP-EQUIV="Expires" CONTENT="-1"><META http-equiv="Content-Type" content="text/html; charset=windows-1252"><SCRIPT>var PrevPage="Page_108";var NextPage="Page_110";var CurPage="Page_109";var PageOrder="120";</SCRIPT> <TITLE>Document</TITLE> </HEAD> <BODY BGCOLOR="#FFFFFF"><CENTER><TABLE BORDER=0 WIDTH=100% CELLPADDING=0><TR><TD ALIGN=CENTER> <TABLE BORDER=0 CELLPADDING=2 CELLSPACING=0 WIDTH=100%> <TR> <TD ALIGN=LEFT><A HREF='Page_108.html'>Previous</A></TD> <TD ALIGN=RIGHT><A HREF='Page_110.html'>Next</A></TD> </TR> </TABLE></TD></TR><TR><TD ALIGN=LEFT><P><A NAME='JUMPDEST_Page_109'/><A NAME='{3B5}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0 WIDTH='100%'><TR><TD ALIGN=RIGHT><FONT FACE='Times New Roman, Times, Serif' SIZE=2 COLOR=#FF0000>Page 109</FONT></TD></TR></TABLE><A NAME='{3B6}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=12></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3>relatively poor trial solutions, that is, population members with poor fitness. The first process, reproduction, involves an exchange of information between population members. Selection keeps the size of the population constant but increases the fitness of the next generation.</FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3B7}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=12></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3>Selection is similar to the process of "natural selection" in nature, where only the fittest individuals in the population survive to pass their genetic material on to the next generation. The chance of the genome surviving to the next generation is proportional to its fitness value. For example, let's say you are attempting to determine the setting of <I>x</I> and <I>y</I> coordinates in order to maximize <I>z</I> on a surface. In this instance, your <I>inputs</I> are <I>x</I> and <I>y</I> with <I>z</I> being your <I>output.</I> The first step would be to create a population of random possible solutions, in this case some coordinates being better than others:</FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3B8}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=12></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3><IMG SRC='C0121-01.GIF' BORDER=0 ALT='C0121-01.gif' WIDTH=123 HEIGHT=113></FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3B9}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=12></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3>You next rank your solutions (selection) and keep the best coordinates, which yield the better results:</FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3BA}'/><TABLE CELLPADDING=0 CELLSPACING=0 BORDER=0 WIDTH='100%'><TR><TD HEIGHT=12></TD></TR><TR><TD><TABLE CELLSPACING=0 WIDTH=583 CELLPADDING=5><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>1.</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x =</I> 4.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 6.0</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>keep</FONT></TD></TR><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>2.</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x =</I> 3.0</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 5.0</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>keep</FONT></TD></TR><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>3.</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x</I> = 2.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 4.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>eliminate</FONT></TD></TR><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>4.</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x</I> = 2.0</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 4.0</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>eliminate</FONT></TD></TR><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>5.</I></FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x</I> = 1.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 3.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>eliminate</FONT></TD></TR><TR><TD WIDTH=151 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>6.</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>x</I> = 1.3</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2><I>y</I> = 2.5</FONT></TD><TD WIDTH=144 VALIGN=TOP><FONT FACE='Times New Roman, Times, Serif' SIZE=2>eliminate</FONT></TD></TR></TABLE></TD></TR></TABLE><BR><A NAME='{3BB}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=17></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3><B>Crossover</B></FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3BC}'/><TABLE BORDER=0 CELLSPACING=0 CELLPADDING=0><TR> <TD ROWSPAN=5></TD> <TD COLSPAN=3 HEIGHT=12></TD> <TD ROWSPAN=5></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR><TD></TD> <TD><FONT FACE='Times New Roman, Times, Serif' SIZE=3>When <I>crossover</I> occurs, two strings exchange information that yields new combinations of scenarios. Survival is based on choosing the genomes in a random way proportional to their fitness. This involves the selection of two individuals, the selection of a crossover site, and the exchange of values between the two strings. Crossover, which occurs in nature, creates two new genomes from two existing ones by gluing together pieces of each genome. When population members mate, they cross gene values over to their partner, resulting in a "trade" of values.</FONT><FONT FACE='Times New Roman, Times, Serif' SIZE=3 COLOR=#FFFF00><!-- continue --></FONT></TD><TD></TD></TR><TR> <TD COLSPAN=3></TD></TR><TR> <TD COLSPAN=3 HEIGHT=1></TD></TR></TABLE><A NAME='{3BD}'/></FORM></P></TD></TR></TABLE><P><FONT SIZE=0 COLOR=WHITE></CENTER><A NAME="bottom"> </A><!-- netLibrary.com Copyright Notice --> </BODY></HTML>⌨️ 快捷键说明
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