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| 6 | <title>PALM chapter 4.5.6</title> |
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| 19 | <h4 style="line-height: 100%;"><font size="4">4.5.6 Plots of compressed |
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| 20 | 3d volume data with AVS</font></h4> |
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| 21 | <p style="line-height: 100%;">Files containing 3d volume data usually |
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| 22 | need large amounts of disc space. For parallel runs, the disc space |
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| 23 | requirement can |
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| 24 | be clearly reduced if the data are output in compressed format (note: |
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| 25 | currently a data |
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| 26 | compression is permitted only for parallel runs on Cray-T3E). Data |
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| 27 | compression |
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| 28 | can switched on by setting the initialization parameter <a |
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| 29 | href="chapter_4.2.html#do3d_compress">do3d_compress</a> |
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| 30 | = <i>.TRUE.</i> and by assigning the desired accuracy (number of |
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| 31 | significant digits) via <a href="chapter_4.2.html#do3d_precision">do3d_precision</a>. |
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| 32 | A separate accuracy must be assigned for each individual quantity. |
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| 33 | Using uncompressed data, each grid point value is |
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| 34 | represented by a 32-bit real number, in case of compression the grid |
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| 35 | point values are represented by integers whose length depends |
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| 36 | on the desired accuracy (in general clearly smaller than 32 bits). |
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| 37 | The individual grid point values are packed into 32-bit integers and |
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| 38 | output. To plot these compressed data the following output command must |
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| 39 | be inserted into the |
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| 40 | <span style="font-weight: bold;">mrun</span> configuration file<b> </b>(in |
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| 41 | addition to the steps described |
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| 42 | in <a href="chapter_4.5.5.html">chapter |
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| 43 | 4.5.5</a>): </p> |
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| 44 | <ul> |
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| 45 | <pre style="margin-bottom: 0.5cm; line-height: 100%;"><font |
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| 46 | style="font-size: 10pt;" size="2">OC:[[ -f PLOT3D_COMPRESSED ]] && tar cf PLOT3D_DATA PLOT3D_DATA_*</font></pre> |
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| 47 | </ul> |
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| 48 | <p style="line-height: 100%;">If a file named <tt><font |
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| 49 | style="font-size: 10pt;" size="2">PLOT3D_COMPRESSED</font></tt> |
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| 50 | exists in the local working directory, <tt><font |
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| 51 | face="Thorndale, serif">t</font></tt><font face="Thorndale, serif">he |
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| 52 | files produ</font>ced by the individual processors are packed into one |
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| 53 | file (<tt><font style="font-size: 10pt;" size="2">PLOT3D_DATA</font></tt>) |
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| 54 | using the "tar" |
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| 55 | command. The flag file |
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| 56 | <tt><font size="2">PLOT3D_COMPRESSED </font></tt>is created by PALM |
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| 57 | whenever data in compressed form is to be output. For |
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| 58 | uncompressed output, the individual files have to be joined via the |
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| 59 | program <tt><font style="font-size: 10pt;" size="2">combine_plot_fields.x</font> |
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| 60 | </tt>. In this case, an additional output command is also necessary |
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| 61 | (see chapter 4.5.5). For compressed output, this output command may |
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| 62 | remain |
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| 63 | unchanged in the configuration file, since <tt><font |
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| 64 | style="font-size: 10pt;" size="2">combine_plot_fields.x</font></tt> |
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| 65 | recognizes the |
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| 66 | ex<font face="Thorndale, serif">isten</font>ce of <tt><font |
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| 67 | style="font-size: 10pt;" size="2">PLOT3D_COMPRESSED</font></tt> |
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| 68 | and carries out no actions in such cases. </p> |
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| 69 | <p style="line-height: 100%;">The file connection statements for the |
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| 70 | local file <a href="chapter_3.4.html#PLOT3D_DATA">PLOT3D_DATA</a> |
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| 71 | and all further necessary statements to create plots of 3d volume |
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| 72 | data can be found in <a href="chapter_4.5.5.html">chapter |
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| 73 | 4.5.5</a>. </p> |
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| 74 | <p style="line-height: 100%;">After been transferred to the local |
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| 75 | computer |
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| 76 | of the user, the tar file with the compressed data cannot be read |
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| 77 | with the usual <span style="font-weight: bold;">AVS</span> module |
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| 78 | read field. Alternatively, |
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| 79 | the module read_compressed_field particularly developed |
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| 80 | for this purpose must be used. This module is located in a module |
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| 81 | library under: </p> |
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| 82 | <pre style="margin-bottom: 0.5cm; line-height: 100%;"><font |
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| 83 | style="font-size: 10pt;" size="2">http://www.muk.uni-hannover.de/~raasch/PALM_group/AVS/Libraries/palm</font></pre> |
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| 84 | <p style="line-height: 100%;">This module must be loaded within AVS |
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| 85 | (network editor - > module |
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| 86 | tools - > read module library) and then it can be used like all |
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| 87 | other modules. <a |
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| 88 | href="http://www.muk.uni-hannover.de/institut/people/raasch/PALM_group/AVS/Doc/read_compressed_field.html">Further |
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| 89 | information</a> about using this module is available (e.g. for |
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| 90 | accelerated treatment of compressed data with <span |
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| 91 | style="font-weight: bold;">AVS</span> the module |
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| 92 | <a |
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| 93 | href="http://www.muk.uni-hannover.de/institut/people/raasch/PALM_group/AVS/Doc/write_compressed_field.html">write_compressed_field</a> |
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| 94 | is available). <br> |
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| 95 | <br> |
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| 96 | </p> |
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| 106 | <p style="line-height: 100%;"> <i>Last change: </i> 20/04/05 |
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| 107 | (SR)</p> |
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