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!
! Copyright (C) 2013 Quantum ESPRESSO group
! This file is distributed under the terms of the
! GNU General Public License. See the file `License'
! in the root directory of the present distribution,
! or http://www.gnu.org/copyleft/gpl.txt .
!
!----------------------------------------------------------------------------
MODULE mp_bands
!----------------------------------------------------------------------------
!
USE mp, ONLY : mp_barrier, mp_bcast, mp_size, mp_rank, mp_comm_split
USE parallel_include
!
IMPLICIT NONE
SAVE
!
! ... Band groups (processors within a pool of bands)
! ... Subdivision of pool group, used for parallelization over bands
!
INTEGER :: nbgrp = 1 ! number of band groups
INTEGER :: nproc_bgrp = 1 ! number of processors within a band group
INTEGER :: me_bgrp = 0 ! index of the processor within a band group
INTEGER :: root_bgrp = 0 ! index of the root processor within a band group
INTEGER :: my_bgrp_id = 0 ! index of my band group
INTEGER :: inter_bgrp_comm = 0 ! inter band group communicator
INTEGER :: intra_bgrp_comm = 0 ! intra band group communicator
!
! ... "task" groups (for band parallelization of FFT)
!
INTEGER :: ntask_groups = 1 ! number of proc. in an orbital "task group"
!
! ... The following variables not set during initialization but later
!
INTEGER :: ibnd_start = 0 ! starting band index
INTEGER :: ibnd_end = 0 ! ending band index
!
CONTAINS
!
!----------------------------------------------------------------------------
SUBROUTINE mp_start_bands( nband_, ntg_, parent_comm )
!---------------------------------------------------------------------------
!
! ... Divide processors (of the "parent_comm" group) into nband_ pools
! ... Requires: nband_, read from command line
! ... parent_comm, typically processors of a k-point pool
! ... (intra_pool_comm)
!
IMPLICIT NONE
!
INTEGER, INTENT(IN) :: nband_, parent_comm
INTEGER, INTENT(IN), OPTIONAL :: ntg_
!
INTEGER :: parent_nproc = 1, parent_mype = 0
!
#if defined (__MPI)
!
parent_nproc = mp_size( parent_comm )
parent_mype = mp_rank( parent_comm )
!
! ... nband_ must have been previously read from command line argument
! ... by a call to routine get_command_line
!
nbgrp = nband_
!
IF ( nbgrp < 1 .OR. nbgrp > parent_nproc ) CALL errore( 'mp_start_bands',&
'invalid number of band groups, out of range', 1 )
IF ( MOD( parent_nproc, nbgrp ) /= 0 ) CALL errore( 'mp_start_bands', &
'n. of band groups must be divisor of parent_nproc', 1 )
!
! ... Set number of processors per band group
!
nproc_bgrp = parent_nproc / nbgrp
!
! ... set index of band group for this processor ( 0 : nbgrp - 1 )
!
my_bgrp_id = parent_mype / nproc_bgrp
!
! ... set index of processor within the image ( 0 : nproc_image - 1 )
!
me_bgrp = MOD( parent_mype, nproc_bgrp )
!
CALL mp_barrier( parent_comm )
!
! ... the intra_bgrp_comm communicator is created
!
CALL mp_comm_split( parent_comm, my_bgrp_id, parent_mype, intra_bgrp_comm )
!
CALL mp_barrier( parent_comm )
!
! ... the inter_bgrp_comm communicator is created
!
CALL mp_comm_split( parent_comm, me_bgrp, parent_mype, inter_bgrp_comm )
!
IF ( PRESENT(ntg_) ) THEN
ntask_groups = ntg_
END IF
!
#endif
RETURN
!
END SUBROUTINE mp_start_bands
!
SUBROUTINE init_index_over_band (comm,nbnd)
!
IMPLICIT NONE
INTEGER, INTENT(IN) :: comm, nbnd
INTEGER :: npe, myrank, rest, k
myrank = mp_rank(comm)
npe = mp_size(comm)
rest = mod(nbnd, npe)
k = int(nbnd/npe)
IF ( k >= 1) THEN
IF (rest > myrank) THEN
ibnd_start = (myrank)*k + (myrank+1)
ibnd_end = (myrank+1)*k + (myrank+1)
ELSE
ibnd_start = (myrank)*k + rest + 1
ibnd_end = (myrank+1)*k + rest
ENDIF
ELSE
ibnd_start = 1
ibnd_end = nbnd
ENDIF
END SUBROUTINE init_index_over_band
!
END MODULE mp_bands
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