!--------------------------------------------------------------------------------------------------
!> @author Franz Roters, Max-Planck-Institut für Eisenforschung GmbH
!> @author Philip Eisenlohr, Max-Planck-Institut für Eisenforschung GmbH
!> @author Sharan Roongta, Max-Planck-Institut für Eisenforschung GmbH
!> @brief Managing of parameters related to numerics
!--------------------------------------------------------------------------------------------------
module numerics
  use prec
  use IO
  use YAML_types
  use YAML_parse

#ifdef PETSc
#include <petsc/finclude/petscsys.h>
   use petscsys
#endif
!$ use OMP_LIB

  implicit none
  private
  
  class(tNode), pointer, protected, public :: &
    numerics_root                                                                                   !< root pointer storing the numerics YAML structure 
  integer, protected, public    :: &
    worldrank                  =  0, &                                                              !< MPI worldrank (/=0 for MPI simulations only)
    worldsize                  =  1                                                                 !< MPI worldsize (/=1 for MPI simulations only)
  integer(4), protected, public :: &
    DAMASK_NumThreadsInt       =  0                                                                 !< value stored in environment variable DAMASK_NUM_THREADS, set to zero if no OpenMP directive

  public :: numerics_init

contains


!--------------------------------------------------------------------------------------------------
!> @brief reads in parameters from numerics.config and sets openMP related parameters. Also does
! a sanity check
!--------------------------------------------------------------------------------------------------
subroutine numerics_init

!$ integer ::                                gotDAMASK_NUM_THREADS = 1
  integer :: ierr
  character(len=:), allocatable :: &
    numerics_input, &
    numerics_inFlow
  logical :: fexist
!$ character(len=6) DAMASK_NumThreadsString                                                         ! environment variable DAMASK_NUM_THREADS

#ifdef PETSc
  call MPI_Comm_rank(PETSC_COMM_WORLD,worldrank,ierr);CHKERRQ(ierr)
  call MPI_Comm_size(PETSC_COMM_WORLD,worldsize,ierr);CHKERRQ(ierr)
#endif
  write(6,'(/,a)') ' <<<+-  numerics init  -+>>>'

!$ call GET_ENVIRONMENT_VARIABLE(NAME='DAMASK_NUM_THREADS',VALUE=DAMASK_NumThreadsString,STATUS=gotDAMASK_NUM_THREADS)   ! get environment variable DAMASK_NUM_THREADS...
!$ if(gotDAMASK_NUM_THREADS /= 0) then                                                              ! could not get number of threads, set it to 1
!$   call IO_warning(35,ext_msg='BEGIN:'//DAMASK_NumThreadsString//':END')
!$   DAMASK_NumThreadsInt = 1_4
!$ else
!$   read(DAMASK_NumThreadsString,'(i6)') DAMASK_NumThreadsInt                                      ! read as integer
!$   if (DAMASK_NumThreadsInt < 1_4) DAMASK_NumThreadsInt = 1_4                                     ! in case of string conversion fails, set it to one
!$ endif
!$ call omp_set_num_threads(DAMASK_NumThreadsInt)                                                   ! set number of threads for parallel execution

  numerics_root => emptyDict
  inquire(file='numerics.yaml', exist=fexist)
  
  if (fexist) then
    write(6,'(a,/)') ' using values from config file'
    flush(6)
    numerics_input =  IO_read('numerics.yaml')
    numerics_inFlow = to_flow(numerics_input)
    numerics_root =>  parse_flow(numerics_inFlow)
  endif

!--------------------------------------------------------------------------------------------------
! openMP parameter
 !$  write(6,'(a24,1x,i8,/)')   ' number of threads:      ',DAMASK_NumThreadsInt

end subroutine numerics_init

end module numerics