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Dear Comunity,<br>
<p>I modified the local_dos.f90 file (see attached file) stored in
the PP/src folder to download the wavefunctions of a system I'm
currently studying.</p>
<p>In particular, I'm running QE on a CINECA supercomputer because
my system contains more than 600 atoms, and I need to run my
computations on several nodes.</p>
<p>My minor modification works well, but I'm facing some problems
regarding the parallelization during the I/O.</p>
<p>For example, If I ask my modified pp.x to write down a single wfc
computed at gamma at fixed band index (say n=1), I obtain a file
with 551981 real and imaginary parts of the coefficients of the
Plane waves expansion stored. <br>
</p>
<p>However, it takes more than 4 minutes to accomplish this task
using just 1 node, and since the default number of bands is 5747,
it takes about 22988 minutes = 383 hours = 15 days to download all
the wfcs.</p>
<p>Therefore, I decided to run pp.x on multiple nodes. I realized
the number of coefficients saved in the various files is halved
every time the number of nodes is doubled, and the same also
happens when the values of n-tasks-per-node and CPU-per-tasks are
not 1 and 48, respectively (each CINECA node contains 2 CPU with
24 cores each). <br>
</p>
<p>Since I don't know how the I/O is parallelized in QE, could
someone suggest how to modify the file so I can use more nodes and
avoid that part of the files is not overwritten?</p>
<p>The only parts of local_dos.f90 that I have modified are the ones
between the following commented lines</p>
<p><i><br>
</i></p>
<p><i>!##################################################################</i><i><br>
</i><i>!!!NEW: print wave functions in G space and corresponding G
vectors</i><i><br>
</i></p>
<p><i>.</i></p>
<p><i>.</i></p>
<p><i>.</i></p>
<p><i>!!!NEW: print wave functions in G space and corresponding G
vectors</i></p>
<p><i>!----------------------------------------------------------------------------------------------------------</i></p>
<p><br>
</p>
<p>So each modification begins with multiple hashes and ends with
numerous dashes.</p>
<p>My concern is that the WRITE statements I have used are not the
right ones when performing computations over several nodes.</p>
<p>Do I have to open multiple files, one for each node involved?</p>
<p><br>
</p>
<p>Best regards,<br>
</p>
<p>Riccardo Piombo<br>
<br>
<font size="2">Post doc researcher in Condensed Matter Physics at
Sapienza University of Rome</font></p>
<p><br>
</p>
<p><br>
</p>
<p><br>
</p>
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