Hello Raffaello,
the first thing you should do, is be sure that your are writing to some
high performance filesystem. This is often called scratch in computing
centers, to be sure you should ask the people responsible.
cheers
On 9/30/20 4:04 PM, Raffaello Bianco wrote:
Dear QE users and developers,
I am doing an electron-phonon coupling calculation in this way (I am
using QE v 6.6).
First, I have done an scf calculation. Then, I have done a phonon
calculation where I have printed the dvscf files, with
fildvscf = 'dvscf'
Subsequently, I have done the electron-phonon calculation changing the
k-mesh grid, with
trans = .false.
electron_phonon = 'simple'
The calculation ends correctly, but for some q points I have noticed a
huge difference between
CPU and Wall time, like
PHONON : 15h55m CPU 3d18h56m WALL
From the report at the end of the output, the I/O davcio routine seems
to be the
"guilty":
General routines
davcio : 107.89s CPU 263856.08s WALL ( 520331 calls)
Parallel routines
Electron-phonon coupling
elphon : 41730.55s CPU 309708.87s WALL ( 1 calls)
elphel : 41671.20s CPU 309625.04s WALL ( 60 calls)
General routines
davcio : 107.89s CPU 263856.08s WALL ( 520331 calls)
This calculation was done with 10 processors and npool = 10, if I use
40 processors and npool = 10 it is worse (as can probably be expected
due to the higher number of I / O operations). I have looked at the
documentation but I am not very familiar with these things, thus I still
have several doubts. Any suggestions on tests to do or how to improve
performance, or at least comments to clarify the problem, would be
greatly appreciated.
Thank you for your time,
Best,
Raffaello Bianco
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--
Lorenzo Paulatto - Paris
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