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<p>A small addition to Lorenzo's explanation<br>
</p>
<div class="moz-cite-prefix">On 24/04/25 10:46, Lorenzo Paulatto
wrote:<br>
</div>
<blockquote type="cite" cite="mid:0da610eb-72bc-4211-b4c4-d8cd0962c3f3@cnrs.fr">
<blockquote type="cite" cite="mid:b1d96b9670f82777d4801847a7d21711@onera.fr">
<p class="p1"><span class="s1">Parallelization info</span></p>
<p class="p1"><span class="s1"><span class="Apple-converted-space"> </span>--------------------</span></p>
<p class="p1"><span class="s1"><span class="Apple-converted-space"> </span>sticks: <span class="Apple-converted-space"> </span>dense<span class="Apple-converted-space"> </span>smooth <span class="Apple-converted-space"> </span>PW <span class="Apple-converted-space"> </span>G-vecs:<span class="Apple-converted-space"> </span>dense <span class="Apple-converted-space"> </span>smooth<span class="Apple-converted-space"> </span>PW</span></p>
<p class="p1"><span class="s1"><span class="Apple-converted-space"> </span>Min <span class="Apple-converted-space"> </span>287 <span class="Apple-converted-space"> </span>287 <span class="Apple-converted-space"> </span>81<span class="Apple-converted-space"> </span>90079<span class="Apple-converted-space"> </span>90079 <span class="Apple-converted-space"> </span>13189</span></p>
<p class="p1"><span class="s1"><span class="Apple-converted-space"> </span>Max <span class="Apple-converted-space"> </span>288 <span class="Apple-converted-space"> </span>288 <span class="Apple-converted-space"> </span>82<span class="Apple-converted-space"> </span>90130<span class="Apple-converted-space"> </span>90130 <span class="Apple-converted-space"> </span>13206</span></p>
<p class="p1"><span class="s1"><span class="Apple-converted-space"> </span>Sum<span class="Apple-converted-space"> </span>2587<span class="Apple-converted-space"> </span>2587<span class="Apple-converted-space"> </span>733 <span class="Apple-converted-space"> </span>810915
<span class="Apple-converted-space"> </span>810915<span class="Apple-converted-space"> </span>118781</span></p>
</blockquote>
<p><br>
</p>
<p>Hello Lorenzo,</p>
<p>the G-vecs are the plane waves, the 3x3 table gives the maximum
and minimum number per CPU and the total number for the charge
density grid (ecutrho), the "smooth" (4xcutwfc) grid, and the
plane-wave (ecutwfc) grid.</p>
</blockquote>
the "dense" G-vecs number is the number of G-vectors inside the
ecutrho sphere in the dense grid (which is the smallest grid that
avoid aliasing errors for functions whose Fourier components vanish
beyond ecutrho), used to expand density and potentials to the needed
accuracy, "smooth" is the number of G-vecs inside the "4*ecutwfc"
sphere in the smooth grid (which is the smallest grid that avoid
aliasing errors for functions whose Fourier components vanish beyond
4*ecutwfc) , used to interpolate the potential on it so that V*psi
can be computed exactly in real space, PW number is the number of
G-vecs inside the ecutwfc sphere in the smooth grid, used to inject
psi on the fft grid when going from G->R and extract hpsi when
going from R->G. check the attached pdf, hope it may be useful
(discard last slide which is not valid anymore). <br>
<blockquote type="cite" cite="mid:0da610eb-72bc-4211-b4c4-d8cd0962c3f3@cnrs.fr">
<p>The sticks, are the subdivisions of the plane waves over which
the parallelization occurs, i.e. the charge is subdivided in
2587 sticks and every CPU inside a pool gets 287 or 288 to do
Fourier transforms (they used to be called planes, I guess it
now depends if you are using "pencil decomposition" or not)</p>
</blockquote>
<p>in reciprocal space G-vectors assigned to an mpi process are
organized in sticks or pencils, in real space they are organized
in planes.</p>
<p>sticks are assigned to different mpi processes trying to have a
balanced distribution, because they are the number of 1d fft to be
performed, and in term of contained G-vectors, because this is the
leading dimension of many g-space arrays (npw), planes in real
space are also distributed in the most balanced possible way, but
this is trivial. <br>
</p>
<p>hence "dense" is the number of sticks that intersect the cutoff
sphere in the dense grid assigned to a given mpi process, "smooth"
the same for the "4*ecutwfc" sphere on the smooth grid, "PW" the
same on the smooth grid but for the "ecutwfc" sphere.</p>
<p>HTH</p>
<p>stefano <br>
</p>
<blockquote type="cite" cite="mid:0da610eb-72bc-4211-b4c4-d8cd0962c3f3@cnrs.fr">
<blockquote type="cite" cite="mid:b1d96b9670f82777d4801847a7d21711@onera.fr">
<p>Second, when printing the energies per k-point, a number of G
vectors is given as if it were the number of planewaves ( e.g.
"<span class="s1">k = 0.0833 0.1443 0.0000 (101603</span><span class="s2"> PWs</span><span class="s1">) <span class="Apple-converted-space"> </span>bands (ev):" ).
What does this number actually refer to?</span></p>
</blockquote>
<p>It is in fact the number of plane waves used to expand the
wvafunction at that k-point.</p>
<p>The condition to include a plane wave is that (G+k)^2 <
ecutwfc/ħ, which defines a sphere in reciprocal space, with G
being a multiple of the reciprocal axis vectors and k is smaller
than any G. So the number varies with the k-point. Then, in
order to do FFT, all the G from all the spheres are combined and
padded with extra point to make a parallelogram. <br>
</p>
<p>You take a parallelogram of twice the side in order to fit
|psi|^2, and if a larger ecutrho has been defined this will
determine a third grid with |G|^2 < ecutrho/ħ<br>
</p>
<p>hth<br>
</p>
<blockquote type="cite" cite="mid:b1d96b9670f82777d4801847a7d21711@onera.fr">
<p><span class="s1">Last question: how all these sets are
related to the values of ecutwfc and ecutrho ? <br>
</span></p>
</blockquote>
<p>should be explained above.<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:b1d96b9670f82777d4801847a7d21711@onera.fr">
<p><span class="s1">Many thanks! </span></p>
<p><br>
</p>
<div id="signature">-- <br>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Dr.
Lorenzo Sponza<br>
<br>
Chargé de Recherche au CNRS<br>
Université Paris-Saclay, ONERA, CNRS Laboratoire d'étude des
microstructures (LEM)<br>
29 Avenue de la division Leclerc, 92322 Châtillon<br>
Tel: +33146734464<br>
<br>
ETSF Research Team Leader <br>
European Theoretical Spectroscopy Facility<br>
17 Sart-Tilman B-4000 Liège, Belgium</div>
</div>
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<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://people.impmc.fr/lpaulatto/" class="moz-txt-link-freetext" moz-do-not-send="true">http://people.impmc.fr/lpaulatto/</a>
- <a href="https://anharmonic.github.io/" class="moz-txt-link-freetext" moz-do-not-send="true">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05</small></div>
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The Quantum ESPRESSO Foundation stands in solidarity with all civilians worldwide who are victims of terrorism, military aggression, and indiscriminate warfare.
--------------------------------------------------------------------------------
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
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