Editing Gamma-point-only

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The '''''gamma''-point-only''' version of VASP is a "simplified" binary which is faster for calculations performed with integration solely over the gamma-point of the Brillouin zone. It runs "faster" for this specific settings of the KPOINTS file.

The official manual page can be found [http://cms.mpi.univie.ac.at/vasp/vasp/Pre_compiler_flags_overview_parallel_version_Gamma_point_only_version.html here].

Now what does it mean running "faster"? I did a short check for 4 calculations and summarized the results in the table below. The conventional binary is denoted as "complex" and the gamma-point-only binary is instinctively abbreviated as "gamma":

<p align="center" style="width:100%">
{| border="1" style="text-align:center;" cellpadding="4" 
 |+ '''CPU time test on tekla2 cluster'''
 |- 
 | '''job type'''
 | '''queue'''
 | '''# of cores [-]'''
 | '''complex [hours]'''
 | '''gamma [hours]'''
 | '''acceleration [%]'''
 |- 
 | relaxation (<TT>IBRION=1</TT>)
 | c8m24_ompi
 | 8
 | 0.28
 | 0.17
 | 39
 |- 
 | TS ''via'' [[IDM]] (<TT>IBRION=44</TT>)
 | c8m24_ompi
 | 8
 | 6.10
 | 4.26
 | 30
 |- 
 | relaxation (<TT>IBRION=1</TT>)
 | c4m8_ompi
 | 8
 | 0.56
 | 0.42
 | 26
 |- 
 | vibrations (<TT>IBRION=5</TT>)
 | c8m24_ompi
 | 8
 | 0.84
 | 0.69
 | 19
 |}
</p>

The values are given for 5.2.12 and 5.2.12_GAMMA binaries as compiled by Mart&iacute;n at the moment. I did not happen to find any difference in the total energy, i.e. the accuracy is retained. 

I encourage you to use the gamma-point-only version using
 module load vasp/5.2.12_GAMMA
in your SGE script file.

[[User:Dkarhanek|Dkarhanek]] 12:00, 13 September 2011 (CEST)