Global settings

Global settings are general parameters which are valid throughout the whole simulation.

!----------------------------------------------------------!
$global-settings                                 optional  !
                                                           !
 output-directory              character         required  !
 number-of-parallel-threads    integer           optional  !
 OpenMP-stacksize              integer           optional  !
 debug-level                   integer           optional  !
                                                           !
$end_global-settings                             optional  !
!----------------------------------------------------------!

Syntax

!----------------------------------------------------------!
$global-settings                                           !
                                                           !
 output-directory             = output_1/                  !
 number-of-parallel-threads   = 2                          !
!OpenMP-stacksize             =  1048576                   !  1048576 bytes =  1 MB (MiB)
!OpenMP-stacksize             = 16777216                   ! 16777216 bytes = 16 MB (MiB)
 OpenMP-stacksize             = 67108864                   ! 67108864 bytes = 64 MB (MiB)
 debug-level                  = 0                          !
                                                           !
$end_global-settings                                       !
!----------------------------------------------------------!

The whole output will be written into the folder output_1/....

Further example:
 output-directory             = output/QuantumDot1/        !
 

If no directory should be specified use either of the following:
 output-directory             = ''
 output-directory             = .
 output-directory             = .\
 output-directory             = ./
 output-directory             =  \
 output-directory             =  /
 

The default output directory has the name output/.

Alternative: Use command line argument (higher priority).

  nextnano3.exe -outputdirectory output_1/ -threads 2
  nextnano3.exe -outputdirectory ./

Hint: This can be used to write batch scripts (*.bat).

Example:  temperature_script.bat

    nextnano3.exe -inputfile HEMT_100K.in -outputdirectory output_100K/
    nextnano3.exe -inputfile HEMT_200K.in -outputdirectory output_200K/
    nextnano3.exe -inputfile HEMT_300K.in -outputdirectory output_300K/
 

 

Parallelization

The number of parallel threads specifies
- the number of parallel threads that are used within OpenMP parallelization
- the number of parallel images (=threads) that are used within Coarray Fortran parallelization.

Note: Numerical libraries like Intel's Math Kernel Library (MKL) detect the number of cores automatically.

Parallel code within nextnano³ is available for
- CBR:  $CBR-current
- NEGF: $global-parameters-NEGF

Usage:
 number-of-parallel-threads = 1  ! should be the optimum on single-core CPUs
 number-of-parallel-threads = 2  ! should be the optimum on dual-core CPUs
 number-of-parallel-threads = 4  ! should be the optimum on quad-core CPUs
 number-of-parallel-threads = 24 ! should be the optimum on 24-core CPUs
LAPACK and BLAS routines contained in the MKL library are already parallelized.
So it could be that the number of parallel threads should be chosen smaller than the number of cores, depending on the actual device and algorithm used in the simulation.

!OpenMP-stacksize             = 16777216                   ! 16777216 bytes = 16 MB (MiB)
 OpenMP-stacksize             = 67108864                   ! 67108864 bytes = 64 MB (MiB)
This command sets the stacksize for individual threads used in OpenMP in units of [bytes].
This corresponds to the environment variable OMP_STACKSIZE.

Debug information

 debug-level = 0  ! 0 =            no debug information at all
               1  ! 1 =     modest debug information
               2  ! 2 =        more debug information
               3  ! 3 = even more debug information

Alternative: Use command line argument (higher priority).

  nextnano3.exe -debuglevel 2