[Wien] Question about accuracy.

[Sorin Lazar]

Dear all,

Few months ago I have started to compare the performance of Wien2k code 
using various libraries and compilers on various platforms.
Using the new goto libraries (P4 and OPTERON) I found some differences in 
the results of the calculation in  comparison with an executable compiled 
with normal atlas_blas library.
For a large case (64 atoms) the difference (see bellow) is around 0.7Ry in 
total energy and decreases at 0.05Ry for a small case (4 atoms) .

My question is if there is any reason to be worried about that?

Thank you,
Sorin

For a big case: (64 atoms)

classical atlas_blas library on various systems (Athlon, Opteron, Alpha )

:ENE : ********** TOTAL ENERGY IN Ry = -127907.383438
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.45402


new GOTO lib (P4 and Opteron) on Opteron:

:ENE : ********** TOTAL ENERGY IN Ry = -127906.677866
FER : F E R M I - ENERGY(TETRAH.M.)= 0.45715



For a small case: (4 atoms)

classical atlas_blas library on various systems (Athlon and Alpha)

:ENE : ********** TOTAL ENERGY IN Ry = -7995.656398
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.48117

new GOTO lib (P4 and Opteron)

:ENE : ********** TOTAL ENERGY IN Ry = -7995.611899
:FER : F E R M I - ENERGY(TETRAH.M.)= 0.48294



************************************************************
Ph.D. Sorin Lazar
National Center for HREM
Department of Materials Science and Technology
DELFT University of Technology

Rotterdamseweg 137
2628 AL Delft
the Netherlands

phone: +31 (0)15 2788397
e-mail: sorinl at hrem.stm.tudelft.nl
         S.Lazar at tnw.tudelft.nl

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