[Wien] NMATMAX parameter

[Bertoni Giovanni]

I know what it is written on the manual at page 145
NMATMAX is the maximum dimension of the matrix you can diagonalize in
the calculations
crude extimation are:
NMATMAX = 5000  you can have to allocate in memory about 500 MB, that
becomes 1000 MB = 1 GB in complex calculations (you have complex numbers
instead of real numbers if you calculate system without inversion
symmetry, I think).
NMATMAX = 10000 means about  1 GB for a matrix with real numbers, or 2
GB in the case of a complex matrix.

the matrix size increases with the square of the number of atoms per
cell, I think.

it depends on the hardware, so if you put NMATMAX = 10000 and have a
system with 100 atoms per cell without inversion simmetry, you can fill
all the machine memory!

I have compiled with NMATMAX = 10000, but on a machine that can allocate
for a process also 10 GB of mem...

I hope it can be helpful

probably Peter Blaha can help you more.
bye
giovanni



Michael Gurnett a écrit :
> 
> Is the size of NUME at all hardware related, or should one increase this
> value from the default for machines with larger memory. Am about to
> compile on a 2 Gb machine. Was going to use the following parameters
> 
> NMATMAX 20000 real ... 10000 complex
> 
> NUME ???? real ... ???? complex
> 
> Anyone have any suggestions or experience if this is ok
> 
> Thanks
> 
> Michael
> 
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