symgeneigvv()

subroutine, private kronlininv::symgeneigvv ( real(dp), dimension(:,:), intent(in)  A, character, intent(in)  uplo, real(dp), dimension(:,:), intent(in)  Bpd, real(dp), dimension(:), intent(out)  lambda, real(dp), dimension(:,:), intent(out)  U  )

private

Computes eigenvalues and eigenvectors of the generalized symmetric definite eigenproblem. See http://www.netlib.org/lapack/lug/node54.html

No test to check symmetry or positive definiteness is performed.

Parameters

[in]	A	symmetric matrix
[in]	uplo	upper or lower triangle stored
[in]	Bpd	symmetric positive-definite matrix
[out]	lambda	eigenvalues
[out]	U	eigenvectors

Date

10/8/2016 - Initial Version

Definition at line 811 of file kronlininv.f08.

    real(dp),intent(in) :: a(:,:),bpd(:,:)
    character,intent(in) :: uplo
    real(dp),intent(out) :: lambda(:),u(:,:)
    integer :: n,lwork,itype,info
    character :: jobz
    real(dp),allocatable :: work(:),tmpb(:,:)
    ! DSYGV computes all the eigenvalues, and optionally, the eigenvectors
    ! of a real generalized symmetric-definite eigenproblem, of the form
    ! A*x=(lambda)*B*x,  A*Bx=(lambda)*x,  or B*A*x=(lambda)*x.
    ! Here A and B are assumed to be symmetric and B is also
    ! positive definite.
    itype = 3
    jobz = 'V'
    n=size(a,1)
    if ( (size(a,2)/=n) .or. (size(bpd,1)/=n) .or. (size(bpd,2)/=n) ) then
       write(*,*) "symgeneigvv(): Matrices have wrong sizes"
       stop 
    end if
    allocate(tmpb(n,n))
    u = a
    tmpb = bpd
    lwork=3*n-1
    ! lwork=-1 
    ! allocate(work(1))
    ! call DSYGV(itype,jobz,uplo,nm1,U1,nm1,choCm1,nm1,lambda1,work,lwork,info)
    ! deallocate(work)
    allocate(work(lwork))
    call dsygv(itype,jobz,uplo,n,u,n,tmpb,n,lambda,work,lwork,info)
    if (info /= 0) stop 'symgeneigvv(): Matrix eigendecomposition failed!'

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