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<p class="MsoNormal"><span style="font-size:12.0pt">Dan,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Should not be a problem and has been done way back.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Main thing is to make sure you specify corresponding control variable both in the code and in the argument list of the AD tool. Probably easiest is to add that variable in ctrl.h.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">And then of course also have somewhere to write the adjoint variable. Bottom line, don’t use the gentim, genarr array as controls.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">Remember how we bypassed writing control variables to file initially when getting OpenAD to work. Very much the same steps (but easier) apply here.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt">p.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
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<b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Daniel Goldberg <Dan.Goldberg@ed.ac.uk><br>
<b>Date: </b>Friday, February 17, 2023 at 11:30 AM<br>
<b>To: </b>MITgcm Support <mitgcm-support@mitgcm.org><br>
<b>Subject: </b>[MITgcm-support] using (zero-d) scalars as controls with state estimate/optimisation<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black">Hello All<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black">As in the subject, I am wondering if any MITgcm/adjoint users have ever used a (zero-dimensional) scalar (either static, or time dependent) as a control,
and have any examples of doing so or any advice as to whether it is a good idea. As far as I know, it is only possible to use 2D and 3D static and time varying fields.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black">I know that it is possible to ensure that gradients of a genarr2d or gentim2d control are spatially constant e.g. by using a global sum of the control
array and adding to a scalar -- but this does not reduce the size of the gradient passed to lsopt or m1qn3, so im not sure if the results would be similar to a case where we simply consider the gradient of a scalar. So Im not sure if this is a suitable replacement.
Apologies if what Im saying is unclear.<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black">Many thanks<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in;background:white"><span style="font-size:12.0pt;color:black">Dan<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#222222;background:white">--</span><o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222">Daniel Goldberg, PhD (he/him)</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#222222"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222">Reader in Glaciology</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#222222">
<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222">School of Geosciences, University of Edinburgh<br>
</span><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:black">Geography Building, Drummond Street, Edinburgh EH8 9XP</span><span style="font-size:9.5pt;font-family:"Arial",sans-serif;color:#222222"><br>
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em: <a href="mailto:dan.goldberg@ed.ac.uk" target="_blank"><span style="color:#1155CC">dan.goldberg@ed.ac.uk</span></a><br>
web: <a href="https://www.geos.ed.ac.uk/homes/dgoldber" target="_blank"><span style="color:#1155CC">https://www.geos.ed.ac.uk/homes/dgoldber</span></a><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:.5in">The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. Is e buidheann carthannais a th’ ann an Oilthigh Dhùn Èideann, clàraichte an Alba, àireamh clàraidh SC005336.
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