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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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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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