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<p class="MsoNormal">Hello,</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am assembling a MATIJ of size N, where a very large number of rows (and corresponding columns), are zeros. I would like to potentially eliminate them before the solve.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For instance say N=7</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="p1">0 0<span class="apple-converted-space"> </span>0<span class="apple-converted-space">
</span>0 0 0 0</p>
<p class="p1">0 1 -1<span class="apple-converted-space"> </span>0 0 0 0</p>
<p class="p1">0 -1 2<span class="apple-converted-space"> </span>0 0 0 -1</p>
<p class="p1">0 0<span class="apple-converted-space"> </span>0<span class="apple-converted-space">
</span>0 0 0 0</p>
<p class="p1">0 0<span class="apple-converted-space"> </span>0<span class="apple-converted-space">
</span>0 0 0 0</p>
<p class="p1">0 0<span class="apple-converted-space"> </span>0<span class="apple-converted-space">
</span>0 0 0 0</p>
<p class="p1">0 0<span class="apple-converted-space"> </span>-1 0 0 0 1</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would like to reduce it to a 3x3</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">1 -1 0</p>
<p class="MsoNormal">-1 2 -1</p>
<p class="MsoNormal">0 -1 1</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I do know the size N.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Q1) How do I do it?</p>
<p class="MsoNormal">Q2) Is it better to eliminate them as it would save a lot of memory?
</p>
<p class="MsoNormal">Q3) At the moment, I don’t know which rows (and columns) have the zero entries but with some effort I probably can find them. Should I know which rows (and columns) I am eliminating?</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Karthik.</p>
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