MODULE iteration
implicit none
contains

SUBROUTINE iterate(alpha, beta, e, es, rank, omega, smearing, prec, max_step)
    REAL(kind=8), INTENT(in) :: omega, smearing, prec
    INTEGER :: max_step, step, rank, cnt
    COMPLEX(kind=16) :: alpha(rank,rank), beta(rank,rank), omega_mat(rank, rank), green(rank, rank)
    COMPLEX(kind=16), INTENT(inout) ::  e(rank,rank), es(rank,rank)
    step = 0
    omega_mat = 0
    DO cnt=1, rank
        omega_mat(cnt, cnt) = 1.0
    ENDDO
    omega_mat = omega_mat * (omega + (0.0, 1.0) * smearing)
    DO WHILE (minval(abs(alpha)) .gt. prec .or.  minval(abs(beta)) .gt. prec .and. step .lt. max_step)
        green = zInverse(rank, omega_mat - e)
        e = e + matmul(alpha, matmul(green, beta)) + matmul(beta, matmul(green, alpha))
        es = es + matmul(alpha, matmul(green, beta))
        alpha = matmul(alpha, matmul(green, alpha))
        beta = matmul(beta, matmul(green, beta))
        step = step + 1
    ENDDO
END SUBROUTINE iterate

FUNCTION zInverse(n, a)  result(ra)
    INTEGER :: n,lda,ipiv(n),info,lwork
    COMPLEX(kind=16)::a(n,n),ra(n,n),work(n)
    ra=a
    lwork=n
    lda=n
    CALL zgetrf(n, n, ra, lda, ipiv, info)
    IF(info/=0) WRITE(0,*) 'Error occured in zgetrf!'
    CALL zgetri(n, ra, lda, ipiv, work, lwork, info)
    IF(info/=0) WRITE(0,*) 'Error occured in zgetri!'
END FUNCTION zInverse
END MODULE iteration

import numpy as np
import pyiteration
alpha = np.array([[1,0],[0,1]], dtype='complex')
beta = np.array([[1,0],[0,1]], dtype='complex')
e = np.array([[1,0],[0,1]], dtype='complex')
es = np.array([[1,0],[0,1]], dtype='complex')
# f2py is automatically generating rank for me
pyiteration.iteration.iterate(alpha,beta, e, es, 1.0, 0.001, 0.001, 100)

alpha = np.array([[1,0],[0,1]], dtype='complex', order='F')
beta = np.array([[1,0],[0,1]], dtype='complex', order='F')
e = np.array([[1,0],[0,1]], dtype='complex', order='F')
es = np.array([[1,0],[0,1]], dtype='complex', order='F')

real(kind=8) dimension(:,:),intent(in) :: kernel
integer dimension(:,:),intent(in) :: kernelmask