| 1 | <!--
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| 2 | //-----------------------------------------------------------
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| 3 | // Copyright Christian Arnault LAL-Orsay CNRS
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| 4 | // arnault@lal.in2p3.fr
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| 5 | // See the complete license in cmt_license.txt "http://www.cecill.info".
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| 6 | //-----------------------------------------------------------
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| 7 | -->
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| 33 |
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| 34 |
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| 35 | <title>MultiThreaded broadcast utility</title>
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| 36 | </head>
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| 37 |
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| 38 | <font face="Arial, Helvetica" color="#000000">
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| 39 |
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| 40 | <body bgcolor="#ffffff" link="#550088" alink="#007777" alink="#007777">
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| 41 | <h1>MultiThreaded broadcast utility</h1>
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| 42 |
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| 43 | <p>This document presents a multithreaded version of the cmt
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| 44 | broadcast facility.</p>
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| 45 |
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| 46 | <p>This is a standalone program and NOT a new feature of CMT. If
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| 47 | it appears to be safe and reliable, then of course it may become
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| 48 | part of the plain CMT.</p>
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| 49 |
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| 50 | <p>This program (named tbroadcast - for "threaded broadcast")
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| 51 | basically operates very much like "cmt broadcast", ie it accepts
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| 52 | most of the same options and produces the same output.</p>
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| 53 |
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| 54 | <p>Report on the CMT mailing list your experience, bugs, comments,
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| 55 | ... and measurements ! Of course the expected improvement will
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| 56 | largely depend on the type of command and on the number of
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| 57 | processors...</p>
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| 58 |
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| 59 | <hr />
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| 60 | <h2>Principle</h2>
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| 61 |
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| 62 | <blockquote>
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| 63 |
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| 64 | The use network forms a Directed Acyclic Graph [DAG] (or if
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| 65 | there are cycles, they are detected and properly handled).
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| 66 |
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| 67 | <p><b>tbroadcast</b> first gets all "leaves" of the use graph, and
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| 68 | launches the requested command onto them in parallel in
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| 69 | individual [POSIX]threads.</p>
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| 70 |
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| 71 | <p>Then, once all children of a non-leaf package are completed,
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| 72 | the requested command is launched onto this non-leaf package
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| 73 | [still in an individual thread].</p>
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| 74 |
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| 75 | <p>This is recursively repeated until all packages have been
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| 76 | reached.</p>
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| 77 |
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| 78 | <p>At any time the number of active threads is controlled so as
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| 79 | to never exceed a limit [set to 20 threads by default but can be
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| 80 | modified using the <b>-threads=n</b> option]. A local scheduler
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| 81 | maintains a queue of threads when the limit is reached.</p>
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| 82 |
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| 83 | <p>The individual thread activity consists in running the
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| 84 | requested command - as usual - in the context of the reached
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| 85 | package. The difference with the sequential <b>cmt broadcast</b>
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| 86 | of course is that the output of the run is accumulated and
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| 87 | displayed at once when every action is completed [to avoid
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| 88 | intermixing of outputs from different threads].</p>
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| 89 |
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| 90 | <p>When one activity returns an error, the error status is
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| 91 | propagated to its parent which will prematurely complete, but
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| 92 | not before all other simultaneously running threads are actually
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| 93 | completed.</p>
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| 94 |
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| 95 | <p>It's only when the threads of ALL children are completed
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| 96 | (with success or error) that a node either starts (if all
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| 97 | children successfully completed) or immediately terminates (if
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| 98 | one of its children failed).</p>
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| 99 |
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| 100 | </blockquote>
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| 101 |
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| 102 | <hr />
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| 103 |
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| 104 | <h2>How to use it:</h2>
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| 105 |
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| 106 | <blockquote>
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| 107 |
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| 108 | <ul>
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| 109 |
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| 110 | <li> The source kit is available for Linux platforms only from CVS:
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| 111 |
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| 112 | <pre>
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| 113 | > export CVSROOT=:pserver:anonymous@cvsserver.lal.in2p3.fr:/projects/cvs
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| 114 | > cvs login
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| 115 | [no password]
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| 116 | > cd /somewhere
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| 117 | > cvs co -d tbroadcast CMT/tbroadcast
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| 118 | > cd tbroadcast/cmt
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| 119 | > cmt config
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| 120 | > gmake
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| 121 | </pre>
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| 122 |
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| 123 | </li>
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| 124 |
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| 125 | <li> The application is also available for Linux platforms
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| 126 | at CERN:
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| 127 |
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| 128 | <pre>
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| 129 | ${CMTROOT}/../tbroadcast/v1/Linux/tbroadcast
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| 130 | </pre>
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| 131 |
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| 132 | </li>
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| 133 |
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| 134 | <li> The options are:
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| 135 |
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| 136 | <pre>
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| 137 | > tbroadcast [option...] [shell-command]
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| 138 |
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| 139 | where option can be:
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| 140 |
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| 141 | -select="<selection-list>"
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| 142 | -exclude="<exclusion-list>"
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| 143 | -begin=<begin-pattern>
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| 144 | -global Reach packages in all CMTPATH items
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| 145 | -threads=<n> Change the maximum thread number [default is 20]
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| 146 |
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| 147 | <selection-list> is a space-separated list of sub-strings that actual paths of
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| 148 | all reached packages must match
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| 149 |
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| 150 | <exclusion-list> is a space-separated list of sub-strings that actual paths of
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| 151 | all reached packages must NOT match
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| 152 |
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| 153 | <begin-pattern> is a sub-string matching a package path for beginning the broadcast loop
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| 154 |
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| 155 | -select=, -exclude=, -begin= can be combined
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| 156 |
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| 157 | -select=, -exclude= can be accumulated
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| 158 |
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| 159 | </pre>
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| 160 |
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| 161 | <p>If the shell-command is omitted, the broadcast loop
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| 162 | simply traverses the graph, reaching all packages and
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| 163 | doing nothing. This is useful to test the traversal.</p>
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| 164 |
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| 165 | </blockquote>
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| 166 |
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| 167 | <hr />
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| 168 | <h2>Examples</h2>
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| 169 |
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| 170 | <blockquote>
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| 171 |
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| 172 | <i>This example shows how to use tbroadcast in the context of the Atlas project</i>
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| 173 |
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| 174 | <pre>> source setup.sh -tag=7.5.0
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| 175 | > cd .....dist/7.5.0/AtlasRelease/*/cmt
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| 176 | > alias tbroadcast=$CMTROOT/../tbroadcast/v1/Linux/tbroadcast
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| 177 | > tbroadcast -select=/Database/
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| 178 | > tbroadcast -global
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| 179 | > tbroadcast -begin=/StoreGate/
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| 180 |
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| 181 | </pre>
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| 182 |
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| 183 | </blockquote>
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| 184 |
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| 185 | <hr>
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| 186 | <address><a href="mailto:arnault@lal.in2p3.fr">Christian Arnault</a></address>
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| 187 | <!-- Created: Fri Jan 30 12:20:51 CET 2004 -->
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| 188 | <!-- hhmts start -->
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| 189 | Last modified: Fri Jan 30 12:50:46 CET 2004
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