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<p>Hei,</p>
<p>I removed all dependencies to armadillo and other not directly
necessary packages, and attached both CMakeLists.txt and
main-file. Even though I am only having PETSc as main dependence I
still have the same issues. For a scaling factor of 0.1 and a
matrix size of [1024, 1024] it works fine, for a scaling factor of
0.01 on the same matrix the apparent scaling factor is suddenly
1e-8.</p>
<p>Thank you for your help!</p>
<p>Regards,</p>
<p>Roland<br>
</p>
<div class="moz-cite-prefix">Am 06.01.21 um 17:36 schrieb Matthew
Knepley:<br>
</div>
<blockquote type="cite"
cite="mid:CAMYG4G=oHnxt1PhOMKM3SJfxooOesu00M2aX2yjVe-rpBi-pEw@mail.gmail.com">
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<div dir="ltr">On Wed, Jan 6, 2021 at 11:05 AM Roland Richter
<<a href="mailto:roland.richter@ntnu.no"
moz-do-not-send="true">roland.richter@ntnu.no</a>> wrote:<br>
</div>
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<p>Hei,</p>
<p>I ran the program in both versions using "valgrind
--tool=memcheck --leak-check=full --show-leak-kinds=all
<binary> -malloc_debug". I got</p>
<p>==3059== LEAK SUMMARY:<br>
==3059== definitely lost: 12,916 bytes in 32 blocks<br>
==3059== indirectly lost: 2,415 bytes in 2 blocks<br>
==3059== possibly lost: 0 bytes in 0 blocks<br>
==3059== still reachable: 103,511 bytes in 123 blocks<br>
==3059== suppressed: 0 bytes in 0 blocks<br>
</p>
<p>but none of the leaks is related to the
scaling-function itself.</p>
<p>Did I miss something here?</p>
</div>
</blockquote>
<div>Here is my analysis. It is certainly the case that
MatScale() does not mysteriously scale by other numbers.</div>
<div>It is used all over the place in tests, and in the code.
Your test requires another package. Thus, it seems</div>
<div>reasonable to guess that a bad interaction with that
package (memory overwrite, conflicting layout or format,
etc.)</div>
<div>is responsible for the behavior you see.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt </div>
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<div>
<p>Thanks!<br>
</p>
<div>Am 06.01.21 um 15:26 schrieb Matthew Knepley:<br>
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<blockquote type="cite">
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<div dir="ltr">On Wed, Jan 6, 2021 at 2:41 AM Roland
Richter <<a href="mailto:roland.richter@ntnu.no"
target="_blank" moz-do-not-send="true">roland.richter@ntnu.no</a>>
wrote:<br>
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<div>
<p>Hei,</p>
<p>I added one additional function to the code:</p>
<p><i>void test_scaling_petsc_pointer(const Mat
&in_mat,</i><i><br>
</i><i> Mat
&out_mat,</i><i><br>
</i><i> const
PetscScalar &scaling_factor) {</i><i><br>
</i><i> MatCopy (in_mat, out_mat,
SAME_NONZERO_PATTERN);</i><i><br>
</i><i> PetscScalar *mat_ptr;</i><i><br>
</i><i> MatDenseGetArray (out_mat,
&mat_ptr);</i><i><br>
</i><i> PetscInt r_0, r_1;</i><i><br>
</i><i> MatGetLocalSize (out_mat, &r_0,
&r_1);</i><i><br>
</i><i> for(int i = 0; i < r_0 * r_1;
++i)</i><i><br>
</i><i> *(mat_ptr + i) = (*(mat_ptr +
i) * scaling_factor);</i><i><br>
</i><i><br>
</i><i> MatAssemblyBegin (out_mat,
MAT_FINAL_ASSEMBLY);</i><i><br>
</i><i> MatAssemblyEnd (out_mat,
MAT_FINAL_ASSEMBLY);</i><i><br>
</i><i>}</i></p>
<p>When replacing test function <i>test_scaling_petsc()</i>
with <i>test_scaling_petsc_pointer()</i>
everything works as it should, but I do not
understand why.</p>
<p>Do you have any suggestions?</p>
</div>
</blockquote>
<div>The easiest explanation is that you have a
memory overwrite in the code somewhere. Barry's
suggestion to use</div>
<div>valgrind is good.</div>
<div><br>
</div>
<div> Matt </div>
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<div>
<p>Thanks!<br>
</p>
<p><br>
</p>
<div>Am 05.01.21 um 15:24 schrieb Roland
Richter:<br>
</div>
<blockquote type="cite">
<p>Hei,</p>
<p>the code I attached to the original mail
should work out of the box, but requires
armadillo and PETSc to compile/run.
Armadillo stores the data in column-major
order, and therefore I am transposing the
matrices before and after transferring using
.st().</p>
<p>Thank you for your help!</p>
<p>Regards,</p>
<p>Roland<br>
</p>
<div>Am 05.01.21 um 15:21 schrieb Matthew
Knepley:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">On Tue, Jan 5, 2021 at 7:57
AM Roland Richter <<a
href="mailto:roland.richter@ntnu.no"
target="_blank" moz-do-not-send="true">roland.richter@ntnu.no</a>>
wrote:<br>
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hei,<br>
<br>
I would like to scale a given matrix
with a fixed scalar value, and<br>
therefore would like to use
MatScale(). Nevertheless, I observed
an<br>
interesting behavior depending on the
size of the matrix, and currently<br>
I am not sure why.<br>
<br>
When running the attached code, I
intend to divide all elements in the<br>
matrix by a constant factor of 10. If
I have three or fewer rows and<br>
1024 columns, I get the expected
result. If I have four or more rows<br>
(with the same number of columns),
suddenly my scaling factor seems to<br>
be 0.01 instead of 0.1 for the
PETSc-matrix. The armadillo-based
matrix<br>
still behaves as expected.<br>
</blockquote>
<div><br>
</div>
<div>1) It looks like you assume the
storage in your armadillo matrix is
row major. I would be surprised if
this was true.</div>
<div><br>
</div>
<div>2) I think it is unlikely that
there is a problem with MatScale, so I
would guess either you have a memory
overwrite</div>
<div>or are misinterpreting your output.
If you send something I can run, I
will figure out which it is.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex"> I
currently do not understand that
behavior, but do not see any problems<br>
with the code either. Are there any
possible explanations for that
behavior?<br>
<br>
Thank you very much,<br>
<br>
regards,<br>
<br>
Roland Richter<br>
<br>
</blockquote>
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begin their experiments is
infinitely more interesting
than any results to which
their experiments lead.<br>
-- Norbert Wiener</div>
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-- <br>
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<div>What most experimenters take for
granted before they begin their
experiments is infinitely more
interesting than any results to which
their experiments lead.<br>
-- Norbert Wiener</div>
<div><br>
</div>
<div><a
href="http://www.cse.buffalo.edu/~knepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
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<div dir="ltr">
<div>
<div dir="ltr">
<div>What most experimenters take for granted before
they begin their experiments is infinitely more
interesting than any results to which their
experiments lead.<br>
-- Norbert Wiener</div>
<div><br>
</div>
<div><a href="http://www.cse.buffalo.edu/~knepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
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