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<div id="Layer1" style="position:absolute; width:711px; height:21px; z-index:1; top: 10px; background-color: #CCCCCC; layer-background-color: #CCCCCC; border: 1px none #000000; left: 26px"><b>|</b><font face="宋体" size="2"><a href="../text1/text1-0.htm">第一章</a></font><b>|</b><font face="宋体" size="2"><a href="../text2/text2-0.htm">第二章</a></font><b>|</b><font face="宋体" size="2"><a href="../text3/text3-0.htm">第三章</a></font><b>|</b><font face="宋体" size="2"><a href="../text4/text4-0.htm">第四章</a></font><b>|</b><font face="宋体" size="2"><a href="../text5/text5-0.htm">第五章</a></font><b>|</b><font face="宋体" size="2"><a href="../text6/text6-0.htm">第六章</a></font><b>|</b><font face="宋体" size="2"><a href="../text7/text7-0.htm">第七章</a></font><b>|</b><font face="宋体" size="2">第八章</font><b>|</b><font face="宋体" size="2"><a href="../text9/text9-0.htm">第九章</a></font><b>|</b><font face="宋体" size="2"><a href="../text10/text10-0.htm">第十章</a></font><b>|</b><font size="2" face="宋体"><a href="../textA/textA-0.htm">算法分析</a><b><font color="#000000">|</font></b>
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<b><font face="Arial, Helvetica, sans-serif" size="4" color="#FF0000">most of the entries point to the same pages ~
translate the bits into a random sequence</font><font face="Arial, Helvetica, sans-serif" size="4" color="#000000">
<font color="#FF0000">a family of hash function:</font>
<i> hashi : key --> { 0 ... <img src="image/2i-1.gif" width="31" height="20" align="middle"> }, 1 <= i <= d </i>
<font color="#0033CC">hashi </font>-- simply hashi -1 with either a zero or one appended
as the new leading bit of the result
<img src="image/text8-c01.gif" width="178" height="39" align="middle">
<font color="#0033CC">hash ( key, i ) </font>--- a function that produces a random number
of i bits from the identifier key
<font color="#FF0000">□</font>suppose a page identified by i bits overflow, we allocate a new
page and rehash the identifiers into those two pages ( buddies
--low-order i bits in common ).
<font color="#FF0000">□ </font>When the number in two buddy pages is no more than the
capacity of a single page, then we coalesce the two pages into one
<font color="#FF0000">□<font color="#000000">If</font></font><font color="#000000"> </font>the number of bits used > the depth ( the number of bits or
log2 (directory size) ) of the directory, the whole directory doubles
in size and its depth increase by 1.
</font></b></pre>
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