linear_systems.F

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!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright 2000-2024 CP2K developers group <https://cp2k.org>                                   !
!                                                                                                  !
!   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
!--------------------------------------------------------------------------------------------------!
 
! **************************************************************************************************
!> \brief Provides interfaces to LAPACK routines for factorisation and
!>      linear system solving
!> \note
!>      We are using LAPACK interfaces, so please make sure in IBM/AIX you have
!>      the lapack library before essl: "xlf90 ... -llapack -lessl" !!!
!> \par History
!>      none
!> \author JGH (30-5-2001)
! **************************************************************************************************
MODULE linear_systems
 
   USE kinds,                           ONLY: dp
   USE lapack,                          ONLY: lapack_sgesv
#include "../base/base_uses.f90"
 
   IMPLICIT NONE
 
   PRIVATE
 
   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'linear_systems'
 
   PUBLIC :: solve_system
 
CONTAINS
 
! **************************************************************************************************
!> \brief ...
!> \param matrix ...
!> \param mysize ...
!> \param eigenvectors ...
! **************************************************************************************************
   SUBROUTINE solve_system(matrix, mysize, eigenvectors)
 
      REAL(kind=dp), INTENT(INOUT)                       :: matrix(:, :)
      INTEGER, INTENT(IN)                                :: mysize
      REAL(kind=dp), INTENT(INOUT)                       :: eigenvectors(:, :)
 
      INTEGER                                            :: info, lda, ldb, nrhs, ipiv(mysize)
 
      lda = SIZE(matrix, 1)
      ldb = SIZE(eigenvectors, 1)
      nrhs = SIZE(eigenvectors, 2)
 
      CALL lapack_sgesv(mysize, nrhs, matrix, lda, ipiv, &
                        eigenvectors, ldb, info)
      IF (info /= 0) THEN
         cpabort("Error in inversion")
      END IF
 
   END SUBROUTINE solve_system
 
END MODULE linear_systems