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Hi Matt, Thanks so much for the quick reply! Regarding #2, I put some debug statement in my code and what I find is that when I use createWithArray on my Cython-allocated numpy array, the destructor I set for it is no longer called when I delete
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Hi Matt,
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<div>Thanks so much for the quick reply!</div>
<div><br>
</div>
<div>Regarding #2, I put some debug statement in my code and what I find is that when I use <font face="sans-serif"><span style="white-space: pre-wrap;">createWithArray on my Cython-allocated numpy array, the destructor I set for it is no longer called when
I delete the array. (If I don’t use </span></font><span style="font-family: sans-serif; white-space: pre-wrap;">createWithArray then the destructor is triggered.)
</span><font face="sans-serif"><span style="white-space: pre-wrap;">I interpret that to suggest that the petsc4py Vec is somehow ’taking over’ management of the numpy array. But I don’t understand where that could be happening. (I don’t think it has to do with
the actual freeing of memory by PETSc's VecDestroy.) </span></font></div>
<div><span style="font-family: sans-serif; white-space: pre-wrap;"><br>
</span></div>
<div><span style="font-family: sans-serif; white-space: pre-wrap;">createWithArray calls
</span>iarray_s which in turn calls PyArray_FROM_OTF. Could it be there’s something going on there? The numpy documentation is unclear. </div>
<div><br>
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<div>Lisandro: do you have any thoughts on this?</div>
<div><br>
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<div>Thanks,</div>
<div><font face="sans-serif"><span style="white-space: pre-wrap;"><br>
</span></font>
<div>Samar</div>
<div><br>
<blockquote type="cite">
<div>On May 2, 2024, at 11:56 PM, Matthew Knepley <knepley@gmail.com> wrote:</div>
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<div dir="ltr">On Thu, May 2, 2024 at 12:53 PM Samar Khatiwala <<a href="mailto:samar.khatiwala@earth.ox.ac.uk">samar.khatiwala@earth.ox.ac.uk</a>> wrote:<br>
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<pre style="font-family: sans-serif; font-size: 12px; white-space: pre-wrap;">Hello,
I have a couple of questions about createWithArray in petsc4py:
1) What is the correct usage for creating a standard MPI Vec with it? Something like this seems to work but is it right?:
On each rank do:
a = np.zeros(localSize)
v = PETSc.Vec().createWithArray(a, comm=PETSc.COMM_WORLD)
Is that all it takes?</pre>
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<div>That looks right to me.</div>
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<div class="msg1959822169370491940">
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<pre style="font-family: sans-serif; font-size: 12px; white-space: pre-wrap;">2) Who ‘owns’ the underlying memory for a Vec created with the createWithArray method, i.e., who is responsible for managing it and doing garbage collection? In my problem, the numpy array is created in a Cython module where memory is allocated, and a pointer to it is associated with a numpy ndarray via PyArray_SimpleNewFromData and PyArray_SetBaseObject. I have a deallocator method of my own that is called when the numpy array is deleted/goes out of scope/whenever python does garbage collection. All of that works fine. But if I use this array to create a Vec with createWithArray what happens when the Vec is, e.g., destroyed? Will my deallocator be called? </pre>
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<div>No. The PETSc struct will be deallocated, but the storage will not be touched. </div>
<div><br>
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<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
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<div class="msg1959822169370491940">
<div>
<pre style="font-family: sans-serif; font-size: 12px; white-space: pre-wrap;">Or does petsc4py know that it doesn’t own the memory and won’t attempt to free it? I can’t quite figure out from the petsc4py code what is going on. And help would be appreciated.
Thanks very much.
Samar
</pre>
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<div><a href="https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!dXZuKR18IO2hZ4uPEqHaG0Jb0ALPgw1T0dm4HAWfyBfsCvkYTmq7aG7yw3yc-5CVhcFMaUL3WzGM8YHlBTTA_JMs_dYUCTX81-bKyrM$" target="_blank">https://www.cse.buffalo.edu/~knepley/</a></div>
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