[gpaw-users] questions about GPAW installation on a supercomputer

[Vladislav Ivanistsev]

>
> then you can use for example this scalability test
>> https://wiki.fysik.dtu.dk/**gpaw/devel/benchmarks.html#**
>> medium-size-system<https://wiki.fysik.dtu.dk/gpaw/devel/benchmarks.html#medium-size-system>
>> Make sure to run each test few times (take average, or the fastest run)
>> on the nodes exclusively reserved for you when collecting timing results.
>>
>
 Can it be possible that domain decomposition slows down a calculation.
I've got a strange result using most simple GPAW configuration. At 2CPU
computation is faster than at 4CPU (both at one node). What could be the
reason?

///////////////////////////////////////////////

Total number of cores used: 2
Domain Decomposition: 2 x 1 x 1
Diagonalizer layout: Serial LAPACK

Symmetries present: 1
1 k-point (Gamma)
1 k-point in the Irreducible Part of the Brillouin Zone
Linear Mixing Parameter:           0.1
Pulay Mixing with 3 Old Densities
Damping of Long Wave Oscillations: 50

Convergence Criteria:
Total Energy Change:           0.0005 eV / electron
Integral of Absolute Density Change:    0.0001 electrons
Integral of Absolute Eigenstate Change: 4e-08 eV^2
Number of Atoms: 768
Number of Atomic Orbitals: 5888
Number of Bands in Calculation:         1056
Bands to Converge:                      Occupied States Only
Number of Valence Electrons:            2048
                     log10-error:    Total        Iterations:
           Time      WFS    Density  Energy       Fermi  Poisson
iter:   1  15:38:04                  -4005.626127  0      19
iter:   2  15:58:27         -0.9     -3942.630366  0      10
iter:   3  16:18:57         -1.0     -3865.223847  0      12
iter:   4  16:39:25         -1.3     -3865.418828  0      12
iter:   5  16:59:53         -1.8     -3862.644668  0      10
Memory usage: 2.48 GB

///////////////////////////////////////////////

Total number of cores used: 4
Domain Decomposition: 2 x 2 x 1
Diagonalizer layout: Serial LAPACK

Symmetries present: 1
1 k-point (Gamma)
1 k-point in the Irreducible Part of the Brillouin Zone
Linear Mixing Parameter:           0.1
Pulay Mixing with 3 Old Densities
Damping of Long Wave Oscillations: 50

Convergence Criteria:
Total Energy Change:           0.0005 eV / electron
Integral of Absolute Density Change:    0.0001 electrons
Integral of Absolute Eigenstate Change: 4e-08 eV^2
Number of Atoms: 768
Number of Atomic Orbitals: 5888
Number of Bands in Calculation:         1056
Bands to Converge:                      Occupied States Only
Number of Valence Electrons:            2048
                     log10-error:    Total        Iterations:
           Time      WFS    Density  Energy       Fermi  Poisson
iter:   1  15:46:32                  -4005.626127  0      19
iter:   2  16:13:38         -0.9     -3942.630365  0      10
iter:   3  16:40:53         -1.0     -3865.223847  0      12
iter:   4  17:07:51         -1.3     -3865.418828  0      12
iter:   5  17:34:59         -1.8     -3862.644668  0      10
Memory usage: 1.83 GB
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