Hi there, Please help. I was testing calculation of eigenvectors/eigenvalues of a 3x3 hermitian matrx with ZHEEV and got this strange error: all three eigenvectors are OK, but one eigenvalue is WRONG! What is going on here? Here is short Fortran code and the result. !=============================== program simpeMeig IMPLICIT NONE INTEGER :: N, LWORK, LDA, info COMPLEX*16, DIMENSION(3,3) :: MTR, MATRIX COMPLEX*16, DIMENSION(3) :: WORK DOUBLE PRECISION, DIMENSION(3) :: W ! eigenvalues DOUBLE PRECISION, DIMENSION(7):: RWORK N=3 LDA=3 LWORK=5 ! first row: MTR(1,1) = 1 MTR(1,2) = 1 MTR(1,3) = 3 ! second row: MTR(2,1) = 1 MTR(2,2) = 1 MTR(2,3) = -3 ! second row: MTR(3,1) = 3 MTR(3,2) = -3 MTR(3,3) = -3 MATRIX(:,:) =MTR(:,:) PRINT *, MTR(1,:) PRINT *, MTR(2,:) PRINT *, MTR(3,:) CALL zheev('V', 'U', N, MATRIX, LDA, W, WORK, LWORK, RWORK, info) print *, print *, "INFO = ", info print *, print *, "First eigenvalue and eigenvector:" print *, W(1) print *, MATRIX(:,1) print *, print *, "Second eigenvalue and eigenvector:" print *, W(2) print *, MATRIX(:,2) print *, print *, "Third eigenvalue and eigenvector:" print *, W(3) print *, MATRIX(:,3) print *, "=========================================================" end program simpeMeig Result: ========================================================= INFO = 0 First eigenvalue and eigenvector: -6.0000000000000000 (-0.40824829046386307 , 0.0000000000000000 ) ( 0.40824829046386307 , 0.0000000000000000 ) ( 0.81649658092772603 , 0.0000000000000000 ) Second eigenvalue and eigenvector: 2.9999999999999996 ( 0.57735026918962584 , 0.0000000000000000 ) (-0.57735026918962584 , 0.0000000000000000 ) ( 0.57735026918962573 , 0.0000000000000000 ) Third eigenvalue and eigenvector: 64.000000000000000 ( 0.70710678118654746 , 0.0000000000000000 ) ( 0.70710678118654768 , 0.0000000000000000 ) ( 0.0000000000000000 , 0.0000000000000000 ) ========================================================= The third eigenvalue should be 3, and NOT 64. Please help! Thanks.