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109 <h1 class="whs1">Loop nodes</h1>
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111 <p><span style="font-weight: bold;"><B><img src="../i_blue.jpg" x-maintain-ratio="TRUE" width="30px" height="30px" border="0" class="img_whs2">Loop node</B></span> is a
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112 kind of Control nodes. In fact two nodes represent Loop: <span style="font-weight: bold;"><B>start
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113 loop</B></span> and <span style="font-weight: bold;"><B>end loop</B></span> nodes.
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114 Nodes of such type are always InLine nodes. User have to supply this type
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115 of node by service, which will check conditions of end of loop. </p>
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117 <p class="whs3"><span style="font-family: 'Times New Roman', serif;">With
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118 that kind of nodes you may define all kinds of loops:</span></p>
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120 <p class="whs4">
\93for(
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121 initial condition(s) ; end condition(s) ; end loop code )
\94 or </p>
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123 <p class="whs4">
\93while(
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124 end condition )
\94</p>
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126 <p class="whs4">etc
\85</p>
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128 <p class="whs3"> </p>
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130 <p class="whs3"><img src="../loop1.jpg" x-maintain-ratio="TRUE" width="775px" height="360px" border="0" class="img_whs5"></p>
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132 <p class="whs3"> </p>
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134 <ul type="disc" class="whs6">
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136 <li class=kadov-p><p class="whs3"><span
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137 style="font-weight: bold;"><B>Titles of the nodes.</B></span> By default the
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138 name of the service is used. You can change only the name of the Start
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139 Loop node - the name of the End Loop node will be automatically created
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140 as follows: EndOf + "Name of the Start Loop node" .</p></li>
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142 <li class=kadov-p><p class="whs3"><span
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143 style="font-weight: bold;"><B>Status of execution</B></span> shows the state
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144 of the loop. It can be: <span style="font-weight: bold;"><B>Not Started</B></span>,
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145 <span style="font-weight: bold;"><B>Running</B></span>, <span style="font-weight: bold;"><B>Finished</B></span>.</p></li>
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147 <li class=kadov-p><p class="whs3"><span
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148 style="font-weight: bold;"><B>InGate/OutGate</B></span> - control ports of the
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149 loop execution. </p></li>
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151 <li class=kadov-p><p class="whs3"><span
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152 style="font-weight: bold;"><B>Time of execution </B></span>is a time of node
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153 execution in a launched dataflow.</p></li>
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155 <li class=kadov-p><p class="whs3"><span
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156 style="font-weight: bold;"><B>Input/Output ports</B></span>
\96 are BusPorts, which
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157 are processed by Python function. Input ports of the Start Loop node will
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158 get the initial values, which can be processed by underlying function
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159 and will be transferred inside of the loop. Last calculation node of the
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160 loop will put these values to the input port of the End Loop node. If
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161 loop continues then this value will be copied to the Input port of the
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162 Start Loop node, otherwise into output port of the End Loop node.</p></li>
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164 <li class=kadov-p><p class="whs3"><span
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165 style="font-weight: bold;"><B>Control loop ports</B></span>
\96 Control ports of
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166 the loop nodes manage the functioning of the loop and they are not accessible
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167 for the user. <span style="font-weight: bold;"><B>InitLoop</B></span> port launches
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168 the loop. <span style="font-weight: bold;"><B>DoLoop</B></span> port of the Start
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169 Loop node checks whether the end loop condition set in <span style="font-weight: bold;"><B>More
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170 </B></span><span>function of the Loop node</span> has been achieved or not.
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171 The value in this ports is of boolean type. It can be 0 or 1. </p></li>
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174 <p class="whs3"> </p>
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176 <p class="whs7"><img src="../note1.gif" x-maintain-ratio="TRUE" width="36px" height="38px" border="0" class="img_whs8">To create a Loop node you have to define three python functions
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177 which will manage the loop with all input and output arguments (ports)
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181 <p class="whs3"> </p>
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183 <ul type="disc" class="whs6">
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185 <li class=kadov-p><p class="whs3"> <span
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186 style="font-weight: bold;"><B>INIT: </B></span>An
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187 Initialization function which will be executed only when we enter in the
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188 loop for the first time.</p></li>
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191 <p class="whs3"> </p>
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193 <ul type="disc" class="whs6">
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195 <li class=kadov-p><p class="whs3"> <span
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196 style="font-weight: bold;"><B>MORE: </B></span>A
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197 \93More
\94 function which is executed at each execution of the LoopNode even
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198 for the first time. That function will have to return as first output
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199 argument a boolean before output arguments (ports) defined by the user
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200 in the node. If that function value is true the body of the loop will
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201 automatically be executed. If it is false SUPERVISION component will resume
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202 execution after the end of the loop. That first output argument will not
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203 be represented as an output port and will not be used in the graph.</p></li>
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206 <p class="whs3"> </p>
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208 <ul type="disc" class="whs6">
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210 <li class=kadov-p><p class="whs3"><span
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211 style="font-weight: bold;"><B>NEXT: </B></span>A
\93Next
\94 function which is executed
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212 each time that SUPERVISION component resume the execution from the end
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213 of the loop to the beginning.</p></li>
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216 <p class="whs3"> </p>
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218 <p class="whs3">Setting of these functions
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219 is possible from the standard <span style="font-weight: bold;"><B>Add Node</B></span>
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220 dialog box (<a href="adding_nodes.htm">see also Adding nodes</a>):</p>
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222 <p class="whs3"> </p>
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224 <p class="whs3"> <img src="../pics/loopfunctions.jpg" x-maintain-ratio="TRUE" width="404px" height="297px" border="0" class="img_whs9"></p>
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226 <p class="whs3"> </p>
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228 <p class="whs3">Here you can see a simple
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229 example of Python functions set in a Loop node:</p>
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231 <p class="whs3"> </p>
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233 <p class="whs10">def <span style="font-weight: bold;"><B>Init</B></span>(Index,Min,Max,Incr)
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236 <p class="whs10"> if
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237 Min <= Max : </p>
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239 <p class="whs10"> Index
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242 <p class="whs10"> else
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245 <p class="whs10"> Index
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248 <p class="whs10"> return
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249 Index,Min,Max,Incr </p>
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251 <p class="whs10"> </p>
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253 <p class="whs10">def <span style="font-weight: bold;"><B>More</B></span>(Index,Min,Max,Incr)
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256 <p class="whs10"> if
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257 Index < Max : </p>
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259 <p class="whs10"> DoLoop
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262 <p class="whs10"> else
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265 <p class="whs10"> DoLoop
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268 <p class="whs10"> return
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269 DoLoop,Index,Min,Max,Incr </p>
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271 <p class="whs10"> </p>
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273 <p class="whs10">def <span style="font-weight: bold;"><B>Next</B></span>(Index,Min,Max,Incr)
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276 <p class="whs10"> Index
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277 = Index + Incr </p>
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279 <p class="whs10"> return
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280 Index,Min,Max,Incr</p>
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282 <p class="whs3"> </p>
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284 <p class="whs7"><img src="../note1.gif" x-maintain-ratio="TRUE" width="36px" height="38px" border="0" class="img_whs8">Loop nodes have the following particularities:</p>
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286 <p class="whs3"> </p>
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288 <ul type="disc" class="whs6">
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290 <li class=kadov-p><p class="whs3">You
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291 may create <span style="font-weight: bold;"><B>only input ports</B></span> in
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292 the Loop node.</p></li>
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294 <li class=kadov-p><p class="whs3">The
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295 input ports, which have been created in the Start Loop node are automatically
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296 duplicated by SUPERVISION component as output ports of this node.</p></li>
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298 <li class=kadov-p><p class="whs3">SUPERVISION
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299 component automatically adds
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300 the same input and output ports in the End
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301 Loop node as in the Start Loop node.</p></li>
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303 <li class=kadov-p><p class="whs3">If
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304 an output port of the Start Loop node has no link and if the corresponding
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305 input port of the End Loop node has no link, SUPERVISION component automatically
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306 transmits its value to the corresponding End Loop node during execution.
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307 You shouldn't define such links.</p></li>
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309 <li class=kadov-p><p class="whs3">When
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310 SUPERVISION component executes the End Loop node, it automatically transmits
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311 the actual values of the
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312 output ports of the End Loop node to the input ports of the Start Loop
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315 <li class=kadov-p><p class="whs3">In
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316 the body of a loop, an input port of a calculation node may not be linked
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317 from an output port of a node which is not in the body of a loop. That
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318 output port <span style="font-weight: bold;"><B>must be linked</B></span> to
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319 an input port of the Start Loop node. So its value will be available through
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320 the corresponding output port of the Start Loop node.</p></li>
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323 <p class="whs3"> </p>
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