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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">第七章</font><b>|</b><font face="宋体" size="2"><a href="../text8/text8-0.htm">第八章</a></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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<pre align="left"><font face="Arial, Helvetica, sans-serif" size="4" color="#000000"><b>
<font color="#FF0000">buffering algorithm</font>
<i><font size="3" color="#CC0099">step 1:</font></i> input the first block of the k runs setting up k linked
queues each having one block of data.
put the remaining k input blocks into a linked stack of
free input blocks. set ou to 0.
<i><font size="3" color="#CC0099">step 2:</font></i> let lastkey [i] be the last key input from run i. let
nextrun be the run for which lastkey is minimum.if
lastkey [nextrun] < > <img src="image/da1.gif" width="36" height="16" align="middle"> then initiate the input of
the next block from run nextrun.
<i><font size="3" color="#CC0099">step 3:</font></i> use a function kwaymerge to merge records from the
k input queues into the output buffer ou. merging
continues until either the output buffer gets full or a
record with key <img src="image/da1.gif" width="36" height="16" align="middle"> is merged into ou. if, during
this merge , an input buffer becomes empty before
the output buffer gets full or before a <img src="image/da1.gif" width="36" height="16" align="middle"> is merged
into a ou, the kwaymerge advances to the next
bufferon the same queue and returns the empty
buffer to the stack of empty buffers.However , if an
input buffer becomes empty at the same time as the
output buffer gets full or <img src="image/da1.gif" width="36" height="16" align="middle"> is merged into ou,
the empty buffer is left on the queue and kwaymerge
does not advance to the next buffer on the queue.
Rather, the merge terminate.
<font color="#CC0099" size="3"><i>step 4:</i></font> wait for any ongoing disk input/output to complete.
<i><font size="3" color="#CC0099">step 5:</font></i> if an input buffer has been read, add it to the queue
for the appropriate run. Determine the next run to
read from by determining nextrun such that
lastkey[nextrun] is minimum.
<i><font size="3" color="#CC0099">step 6:</font></i> if lastkey [nextrun] <img src="image/da.gif" width="60" height="16" align="middle"> , then initiate reading
the next block from run nextrun into a free input
buffer.
<i><font size="3" color="#CC0099">step 7:</font></i> initiate the writing of output buffer ou. Set ou = 1- ou.
<i><font size="3" color="#CC0099">step 8:</font></i> if a record with key + <img src="image/da1.gif" width="36" height="16" align="middle"> has not been merged into
the output buffer go back to step 3.Otherwise, wait
for the ongoing write to complete and then terminate.
</b></font></pre>
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