[CPMD-list] Disagreement with the test run

[Juerg Hutter]

Hi

The test runs are rather old and it might be that some
default values have changed. But most likely the 
difference comes from different real space grids.
Check the number of grid points used in the calculations.
The program usually chooses the smallest possible grid
compatible with the FFT library. The FFT libraries of 
different vendors and the default library in CPMD
don't allow always for the same grids.

About the defaults: check the number of spline points
used to expand the pseudopotential and the XC functional,
especially was there a tabulation of the functional.

Juerg

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 1 635 4491
Physical Chemistry Institute   FAX   : ++41 1 635 6838
University of Zurich           E-mail: hutter at pci.unizh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Wed, 8 May 2002, Atte Sillanpää wrote:

> Hello all,
> 
> I'm trying to confirm, that my executable CPMD 3.5 is correct. I've downloaded
> and run the 32 water molecule test cases from www.cpmd.org. I get slightly
> different results with the exaple output. I have performed three trial runs with
> differently compiled executables. Namely, one of version 3.4.3 runnning on T3E,
> one compiled with optimization of the code turned on of the 3.5 version on
> IBM-SP4, and finally one of the 3.5 version with the debugging options turned on
> with the IBM-SP4 platform. The results of my runs give practically identical
> results, but these differ from the example output quite a bit. Here are the
> total energies for comparison:
> 
> T3E				-549.3152869
> IBM-SP4 (optimized)		-549.3152208
> IBM-SP4 (debug)			-549.3152208
> sample output (w32_wfSP2)	-548.7794744
> 
> Is this as things should be, i.e. should I worry about the compilations? I guess
> the total energies should not differ this much with different platforms.
> 
> Sincerely,
> 
> Atte
> 
> 	atte.sillanpaa at oulu.fi		+358 (0)8 553 1681 (work), KE 368
> 	Dept. of Physical Chemistry	+358 (0)40 592 7369 (gsm)
> 	Po-BOX 3000
> 	FIN-90014 University of Oulu
> 	FINLAND
>                   |   Entropy requires no maintenance.   |
> 
> 
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