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3<meta http-equiv="CONTENT-TYPE" content="text/html; charset=windows-1252"><title>PALM chapter 4.5.6</title> <meta name="GENERATOR" content="StarOffice 7 (Win32)"> <meta name="AUTHOR" content="Siegfried Raasch"> <meta name="CREATED" content="20041029;13171001"> <meta name="CHANGED" content="20041117;12013945"> <meta name="KEYWORDS" content="parallel LES model"> <style>
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8<body style="direction: ltr;" lang="en-US"><h4 style="line-height: 100%;"><font size="4">4.5.6
9Plots of compressed
103d volume data with AVS</font></h4>
11<p style="line-height: 100%;">Files containing 3d volume
12data usually
13need large amounts of disc space. For parallel runs, the disc space
14requirement can
15be clearly reduced if the data are output in compressed format (note:
16currently a data
17compression is permitted only for parallel runs on Cray-T3E). Data
18compression
19can switched on by setting the initialization parameter <a href="chapter_4.2.html#do3d_compress">do3d_compress</a>
20= <i>.TRUE.</i> and by assigning the desired accuracy
21(number of
22significant digits) via <a href="chapter_4.2.html#do3d_comp_prec">do3d_comp_prec</a>.
23A separate accuracy must be assigned for each individual quantity.
24Using uncompressed data, each grid point value is
25represented by a 32-bit real number, in case of compression the grid
26point values are represented by integers whose length depends
27on the desired accuracy (in general clearly smaller than 32 bits).
28The individual grid point values are packed into 32-bit integers and
29output. To plot these compressed data the following output command must
30be inserted into the
31<span style="font-weight: bold;">mrun</span>
32configuration file<b> </b>(in
33addition to the steps described
34in <a href="chapter_4.5.5.html">chapter
354.5.5</a>): </p>
36<ul> <pre style="margin-bottom: 0.5cm; line-height: 100%;"><font style="font-size: 10pt;" size="2">OC:[[ -f PLOT3D_COMPRESSED ]] &amp;&amp; tar cf PLOT3D_DATA PLOT3D_DATA_*</font></pre></ul>
37<p style="line-height: 100%;">If a file named <tt><font style="font-size: 10pt;" size="2">PLOT3D_COMPRESSED</font></tt>
38exists in the local working directory, <tt><font face="Thorndale, serif">t</font></tt><font face="Thorndale, serif">he
39files produ</font>ced by the individual processors are packed
40into one
41file (<tt><font style="font-size: 10pt;" size="2">PLOT3D_DATA</font></tt>)
42using the "tar"
43command. The flag file
44<tt><font size="2">PLOT3D_COMPRESSED </font></tt>is
45created by PALM
46whenever data in compressed form is to be output. For
47uncompressed output, the individual files have to be joined via the
48program <tt><font style="font-size: 10pt;" size="2">combine_plot_fields.x</font>
49</tt>. In this case, an additional output command is also
50necessary
51(see chapter 4.5.5). For compressed output, this output command may
52remain
53unchanged in the configuration file, since <tt><font style="font-size: 10pt;" size="2">combine_plot_fields.x</font></tt>
54recognizes the
55ex<font face="Thorndale, serif">isten</font>ce of <tt><font style="font-size: 10pt;" size="2">PLOT3D_COMPRESSED</font></tt>
56and carries out no actions in such cases. </p>
57<p style="line-height: 100%;">The file connection
58statements for the
59local file <a href="chapter_3.4.html#PLOT3D_DATA">PLOT3D_DATA</a>
60and all further necessary statements to create plots of 3d volume
61data can be found in <a href="chapter_4.5.5.html">chapter
624.5.5</a>. </p>
63<p style="line-height: 100%;">After been transferred to
64the local
65computer
66of the user, the tar file with the compressed data cannot be read
67with the usual <span style="font-weight: bold;">AVS</span>
68module
69&ldquo;read field&rdquo;. Alternatively,
70the module &ldquo;read_compressed_field&rdquo; particularly
71developed
72for this purpose must be used. This module is located in a module
73library under: </p>
74<pre style="margin-bottom: 0.5cm; line-height: 100%;"><font style="font-size: 10pt;" size="2">http://www.muk.uni-hannover.de/~raasch/PALM_group/AVS/Libraries/palm</font></pre><p style="line-height: 100%;">This module must be loaded within
75AVS
76(network editor - &gt; module
77tools - &gt; read module library) and then it can be used like all
78other modules. <a href="http://www.muk.uni-hannover.de/institut/people/raasch/PALM_group/AVS/Doc/read_compressed_field.html">Further
79information</a> about using this module is available (e.g. for
80accelerated treatment of compressed data with <span style="font-weight: bold;">AVS</span> the module
81<a href="http://www.muk.uni-hannover.de/institut/people/raasch/PALM_group/AVS/Doc/write_compressed_field.html">write_compressed_field</a>
82is available). <br>
83&nbsp; <br>
84&nbsp; </p>
85<hr><p style="line-height: 100%;"><br>
86<font color="#000080"><font color="#000080"><a href="chapter_4.5.5.html"><font color="#000080"><img src="left.gif" name="Grafik1" align="bottom" border="2" height="32" width="32"></font></a><a href="index.html"><font color="#000080"><img src="up.gif" name="Grafik2" align="bottom" border="2" height="32" width="32"></font></a><a href="chapter_4.5.7.html"><font color="#000080"><img src="right.gif" name="Grafik3" align="bottom" border="2" height="32" width="32"></font></a></font></font></p><p style="line-height: 100%;">&nbsp;<i>Last
87change:&nbsp;</i> $Id: chapter_4.5.6.html 197 2008-09-16 15:29:03Z raasch $</p>
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