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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">See this long thread about this issue:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="http://slicer-devel.65872.n3.nabble.com/BRAINS-rigid-registration-td4032229.html">http://slicer-devel.65872.n3.nabble.com/BRAINS-rigid-registration-td4032229.html</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Short summary: There were some performance regressions in mutual information metric computation, threading, etc. that have been recently fixed, so use the latest
ITK version. ITKv4 uses a slightly slower but more accurate optimizer, but if you adjust the number of samples and stopping condition then usually the registration time only increases by about 30-50% (and you might get better quality results).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You can see all the changes that have been done in 3D Slicer and BRAINS repositories to go from a 10x-100x slowdown to an approximately equivalent registration
speed with ITKv4 compared to ITKv3.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Andras<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> Community [mailto:community-bounces@itk.org]
<b>On Behalf Of </b>Jiahui Wang<br>
<b>Sent:</b> Monday, October 06, 2014 10:27 AM<br>
<b>To:</b> insight-users@itk.org<br>
<b>Subject:</b> [ITK] [ITK-users] Speed of ITKv4 based Gradient Descent Optimizer<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Dear All,<o:p></o:p></p>
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<p class="MsoNormal">I modified ImageRegistration8.cxx to run my own rigid registration.<o:p></o:p></p>
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<p class="MsoNormal"><br>
However, I found that the processing time of ITKv4 based RegularStepGradientDescentOptimizer is almost 10 times more than that of ITKv3 based one.
<o:p></o:p></p>
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The program was run on the same machine. The only difference is the ITK libraries.
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Could anyone give me some suggestions to solve this issue?<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Thanks,<o:p></o:p></p>
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<p class="MsoNormal">JW<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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