I am working on QR factorization, the code is working here but my problem is, for example, there is an array dimension(6,4) but I want to decompose dimension(6,2). I use the subroutine(dgeqrf) so Should I use a different one or not? That subroutine is taking the whole matrix but I want to give a different column size because I can decompose the matrix (6,2). I share current result for this program but I want for (6,2) dimension decomposition not (6,4) dimension
!Current result: but I want:
! x x x x x x x x
! 0 x x x 0 x x x
! 0 0 x x 0 0 x x
! 0 0 0 x 0 0 x x
! 0 0 0 0 0 0 x x
! 0 0 0 0 0 0 x x
program decomposition
!CONTAINS
!subroutine Qrdecomposition(A_mat, R)
real(8),dimension(6,4) :: A_mat
!real,dimension(2,2),intent(inout)
real(8),dimension(6,4) :: R
!real,dimension(2,2),intent(out)
real(8),dimension(6,4) :: A
integer :: M,N,LDA,LWORK,INFO,i,j
real(8),allocatable, dimension(:,:) :: TAU
real(8),allocatable, dimension(:,:) :: WORK
external dgeqrf
M=6
N=4
LDA=6
LWORK=4
INFO=0
A_mat(1,:)=[2,1,2,6 ]
A_mat(2,:)=[10,4,3,2]
A_mat(3,:)=[1,3,2,9]
A_mat(4,:)=[8,9,2,7]
A_mat(5,:)=[9,5,9,4]
A_mat(6,:)=[9,10,6,6]
A=A_mat
allocate(tau(M,N), work(M,N))
call dgeqrf(M,N,A,LDA,TAU,WORK,LWORK,INFO)
R=A
R(:,:)=0
do i=1,6
do j=i,4
R(i,j)=A(i,j)
end do
end do
print *,R
!end subroutine Qrdecomposition
end program decomposition
!Input
!A =
! 2 1 2 6
!10 4 3 2
! 1 3 2 9
! 8 9 2 7
! 9 5 9 4
! 9 10 6 6
!The result should be like that
! -18.193 -13.851 -10.278 -10.278
! 0 6.336 0.099656 6.5706
! 0 0 0.64881 5.2419
! 0 0 -3.887 -3.5114
! 0 0 4.0589 -1.1447
! 0 0 -0.5819 -5.6624