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<div class="moz-cite-prefix">Dear Giovanni,<br>
<br>
I agree that the message is misleading (and wrong), but nb is not
the number of bands, <br>
nb is the block size used to distribute the hamiltonian (matrix
whose size is number of bands x number of bands).<br>
Whereas desc%n is indeed the number of bands.<br>
The subroutine blk2cyc_redist is called when you are using
internal parallel diagonalization,<br>
which is not block parallelized, but parallelized row by row, then<br>
if the number of processor is less the number of bands, this
internal<br>
parallel subroutine does not work.<br>
<br>
To avoid the problem it should be enough to <br>
use just one processor in the parallelization matrix: -northo 1<br>
<br>
carlo<br>
<br>
Il 11/06/2013 17:47, xiaochuan Ge ha scritto:<br>
</div>
<blockquote
cite="mid:CAJQfR0SPowYJt_h6F6EQbj7U4hwhz9GRhPRhPdPas3mq8qgtRQ@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Dear all,</div>
<div><br>
</div>
<div>I wish this is the right place to ask this question.</div>
<div><br>
</div>
<div>Since, I don't know exactly when, but definitely this year,
when one try to do pw calculation with many cores, the code
will stop and leave this error message:</div>
<div><br>
</div>
<div>
<div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div>
<div> Error in routine blk2cyc_redist (1):</div>
<div> nb less than the number of proc</div>
<div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div>
<div><br>
</div>
<div>The error usually happens when the number of cores is
larger than the number of bands. While USING OLD VERSION OF
THE CODE WON"T HAVE THIS PROBLEM.</div>
<div><br>
</div>
<div>If one looks into the code the meaning of nb seems
misleading. Because in the code, the trigger of this error
is due to this command:</div>
<div><br>
</div>
<div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">
IF( desc%n < nproc ) &</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">
CALL errore( ' cyc2blk_redist ', ' nb less than the
number of proc ', 1 )</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px"><br>
</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">While
the definition of nb at this part was defined as:</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">
nb = desc%nrcx ! leading dimension of the local
matrix block<br>
</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px"><br>
</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">
On the other hand this error happens when the number of
processor is larger than the Number of Bands. </div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px"><br>
</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">
So what NB actually means here? After all, I really don't
understand why the code should stop when I am using 32
cores to calculate a system with 6 bands. The plane wave
parallelization should not care about how many bands there
are in total. </div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px"><br>
</div>
<div
style="font-family:arial,sans-serif;font-size:13.333333969116211px">Could
anyone give any comments, thank you very much. I don't
attach an input here, because one could easily reproduce
this error by calculating any small molecule with many
cores on a parallel machine. </div>
</div>
</div>
<div><br>
</div>
<div>===================<br>
Ge Xiaochuan(Giovanni)<br>
4th year PHD Student<br>
Condensed Matter<br>
SISSA,Italy<br>
===================</div>
</div>
<br>
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<br>
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<br>
<pre class="moz-signature" cols="72">--
Ph.D. Carlo Cavazzoni
SuperComputing Applications and Innovation Department
CINECA - Via Magnanelli 6/3, 40033 Casalecchio di Reno (Bologna)
Tel: +39 051 6171411 Fax: +39 051 6132198
<a class="moz-txt-link-abbreviated" href="http://www.cineca.it">www.cineca.it</a></pre>
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