[Wien] ifort compiler options

Fecher, Gerhard fecher at uni-mainz.de
Wed Aug 6 20:38:22 CEST 2014


Maybe try also:
-fltconsistency
and / or
-fp-model strict (or -fp-model precise might be enough)

I don't have all switches at hand, but there are more about floating point operations found in the manual of the compiler

The warning of INTELL is:
"Note
The options set by the O option may change from release to release." !!!!

There are warnings with many compiler flags that improve speed on cost of consistency 


Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
________________________________________
Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at]" im Auftrag von "Laurence Marks [L-marks at northwestern.edu]
Gesendet: Mittwoch, 6. August 2014 19:26
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] ifort compiler options

Sadly, no surprise. Intel sometimes designs ifort for speed more than accuracy, and they have done some things recently that can reduce accuracy.

Put -O3 immediately after -FR, the order matters. It may be better, or not.

On Aug 6, 2014 12:03 PM, "James Peter" <jsqdmgleap at gmail.com<mailto:jsqdmgleap at gmail.com>> wrote:
Hi,
Recently, I recompiled WIEN2k_13 with -O3 option. (I used to use  the default option O2). The full compiler option is as follows

-FR -mp1 -w -prec_div -pc80 -pad -ip -DINTEL_VML -traceback -assume buffered_io -O3


I calculated the band structure of CsTlCl3 in high symmetry structure (struct file is attached at the end of the email). It is surprising to find splitting at  L point and along W-L. After a miserable week, I changed the compiler option back to O2 and now the splitting at L goes away. A copy of the bands structures calculated with O3 and O2 options can be downloaded here https://www.dropbox.com/s/2xu0mx2z31djns0/testup%20copy.pdf.




Title
F   LATTICE,NONEQUIV.ATOMS:  4225_Fm-3m
MODE OF CALC=RELA unit=ang
 20.451758 20.451758 20.451758 90.000000 90.000000 90.000000
ATOM   1: X=0.25000000 Y=0.25000000 Z=0.25000000
          MULT= 2          ISPLIT= 2
       1: X=0.75000000 Y=0.75000000 Z=0.75000000
Cs         NPT=  781  R0=0.00001000 RMT=   2.50000   Z: 55.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   2: X=0.00000000 Y=0.00000000 Z=0.00000000
          MULT= 1          ISPLIT= 2
Tl1        NPT=  781  R0=0.00000500 RMT=   2.50000   Z: 81.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM   3: X=0.50000000 Y=0.00000000 Z=0.00000000
          MULT= 1          ISPLIT= 2
Tl2        NPT=  781  R0=0.00000500 RMT=   2.50000   Z: 81.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM  -4: X=0.25000000 Y=0.00000000 Z=0.00000000
          MULT= 6          ISPLIT=-2
      -4: X=0.75000000 Y=0.00000000 Z=0.00000000
      -4: X=0.00000000 Y=0.25000000 Z=0.00000000
      -4: X=0.00000000 Y=0.75000000 Z=0.00000000
      -4: X=0.00000000 Y=0.00000000 Z=0.25000000
      -4: X=0.00000000 Y=0.00000000 Z=0.75000000
Cl         NPT=  781  R0=0.00010000 RMT=   2.29      Z: 17.0
LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
                     0.0000000 1.0000000 0.0000000
                    -1.0000000 0.0000000 0.0000000
  48      NUMBER OF SYMMETRY OPERATIONS
 1 0 0 0.00000000
 0-1 0 0.00000000
 0 0-1 0.00000000
       1
 1 0 0 0.00000000
 0 0-1 0.00000000
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       2
-1 0 0 0.00000000
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       3
-1 0 0 0.00000000
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       4
 0 1 0 0.00000000
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       5
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       6
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       7
 0 0 1 0.00000000
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       8
 0 1 0 0.00000000
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       9
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      10
 0 1 0 0.00000000
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      11
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      12
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      13
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      14
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      15
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      16
 1 0 0 0.00000000
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      17
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      21
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      22
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      23
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      25
 0 1 0 0.00000000
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      27
 0 1 0 0.00000000
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      28
 1 0 0 0.00000000
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      29
-1 0 0 0.00000000
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      30
 1 0 0 0.00000000
 0-1 0 0.00000000
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      31
-1 0 0 0.00000000
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      32
 0 0 1 0.00000000
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      33
 0 0 1 0.00000000
 1 0 0 0.00000000
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      34
 0 1 0 0.00000000
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      35
 0 1 0 0.00000000
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      36
 0 0-1 0.00000000
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      37
 0-1 0 0.00000000
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      38
 0 0-1 0.00000000
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      39
 0-1 0 0.00000000
 0 0 1 0.00000000
 1 0 0 0.00000000
      40
 0 0-1 0.00000000
-1 0 0 0.00000000
 0 1 0 0.00000000
      41
 0-1 0 0.00000000
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      42
 0 0-1 0.00000000
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      43
 0-1 0 0.00000000
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      44
 1 0 0 0.00000000
 0 0 1 0.00000000
 0 1 0 0.00000000
      45
 1 0 0 0.00000000
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 0 0 1 0.00000000
      46
-1 0 0 0.00000000
 0 0 1 0.00000000
 0 1 0 0.00000000
      47
-1 0 0 0.00000000
 0 1 0 0.00000000
 0 0 1 0.00000000
      48


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