100 lines
2.8 KiB
HTML
100 lines
2.8 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<META NAME="generator" CONTENT="http://txt2tags.org">
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<LINK REL="stylesheet" TYPE="text/css" HREF="DOC.css">
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<TITLE>GPERF versus CMPH</TITLE>
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</HEAD><BODY BGCOLOR="white" TEXT="black">
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<CENTER>
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<H1>GPERF versus CMPH</H1>
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</CENTER>
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<P>
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You might ask why cmph if <A HREF="http://www.gnu.org/software/gperf/gperf.html">gperf</A>
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already works perfectly. Actually, gperf and cmph have different goals.
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Basically, these are the requirements for each of them:
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</P>
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<UL>
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<LI>GPERF
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<P></P>
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</UL>
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<BLOCKQUOTE>
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- Create very fast hash functions for <B>small</B> sets
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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- Create <B>perfect</B> hash functions
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</BLOCKQUOTE>
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<UL>
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<LI>CMPH
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<P></P>
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</UL>
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<BLOCKQUOTE>
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- Create very fast hash function for <B>very large</B> sets
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</BLOCKQUOTE>
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<BLOCKQUOTE>
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- Create <B>minimal perfect</B> hash functions
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</BLOCKQUOTE>
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<P>
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As result, cmph can be used to create hash functions where gperf would run
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forever without finding a perfect hash function, because of the running
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time of the algorithm and the large memory usage.
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On the other side, functions created by cmph are about 2x slower than those
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created by gperf.
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</P>
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<P>
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So, if you have large sets, or memory usage is a key restriction for you, stick
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to cmph. If you have small sets, and do not care about memory usage, go with
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gperf. The first problem is common in the information retrieval field (e.g.
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assigning ids to millions of documents), while the former is usually found in
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the compiler programming area (detect reserved keywords).
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</P>
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<HR NOSHADE SIZE=1>
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<TABLE ALIGN="center" CELLPADDING="4">
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<TR>
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<TD><A HREF="index.html">Home</A></TD>
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<TD><A HREF="chd.html">CHD</A></TD>
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<TD><A HREF="bdz.html">BDZ</A></TD>
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<TD><A HREF="bmz.html">BMZ</A></TD>
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<TD><A HREF="chm.html">CHM</A></TD>
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<TD><A HREF="brz.html">BRZ</A></TD>
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<TD><A HREF="fch.html">FCH</A></TD>
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</TR>
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</TABLE>
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<HR NOSHADE SIZE=1>
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<P>
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Enjoy!
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</P>
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<P>
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<A HREF="mailto:davi@users.sourceforge.net">Davi de Castro Reis</A>
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</P>
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<P>
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<A HREF="mailto:db8192@users.sourceforge.net">Djamel Belazzougui</A>
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</P>
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<P>
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<A HREF="mailto:fc_botelho@users.sourceforge.net">Fabiano Cupertino Botelho</A>
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</P>
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<P>
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<A HREF="mailto:nivio@dcc.ufmg.br">Nivio Ziviani</A>
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</P>
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<!-- html code generated by txt2tags 2.6 (http://txt2tags.org) -->
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<!-- cmdline: txt2tags -t html -i GPERF.t2t -o docs/gperf.html -->
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</BODY></HTML>
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