Program f08nafe ! F08NAF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dgeev, nag_wp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nb = 64, nin = 5, nout = 6 ! .. Local Scalars .. Complex (Kind=nag_wp) :: eig Integer :: i, info, j, lda, ldvr, lwork, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: a(:,:), vr(:,:), wi(:), work(:), wr(:) Real (Kind=nag_wp) :: dummy(1,1) ! .. Intrinsic Procedures .. Intrinsic :: cmplx, max, nint ! .. Executable Statements .. Write (nout,*) 'F08NAF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n lda = n ldvr = n Allocate (a(lda,n),vr(ldvr,n),wi(n),wr(n)) ! Use routine workspace query to get optimal workspace. lwork = -1 ! The NAG name equivalent of dgeev is f08naf Call dgeev('No left vectors','Vectors (right)',n,a,lda,wr,wi,dummy,1,vr, & ldvr,dummy,lwork,info) ! Make sure that there is enough workspace for blocksize nb. lwork = max((nb+2)*n,nint(dummy(1,1))) Allocate (work(lwork)) ! Read the matrix A from data file Read (nin,*)(a(i,1:n),i=1,n) ! Compute the eigenvalues and right eigenvectors of A ! The NAG name equivalent of dgeev is f08naf Call dgeev('No left vectors','Vectors (right)',n,a,lda,wr,wi,dummy,1,vr, & ldvr,work,lwork,info) If (info==0) Then ! Print solution Do j = 1, n Write (nout,*) If (wi(j)==0.0E0_nag_wp) Then Write (nout,99999) 'Eigenvalue(', j, ') = ', wr(j) Else eig = cmplx(wr(j),wi(j),kind=nag_wp) Write (nout,99998) 'Eigenvalue(', j, ') = ', eig End If Write (nout,*) Write (nout,99997) 'Eigenvector(', j, ')' If (wi(j)==0.0E0_nag_wp) Then Write (nout,99996) vr(1:n,j) Else If (wi(j)>0.0E0_nag_wp) Then Write (nout,99995)(vr(i,j),vr(i,j+1),i=1,n) Else Write (nout,99995)(vr(i,j-1),-vr(i,j),i=1,n) End If End Do Else Write (nout,*) Write (nout,99994) 'Failure in DGEEV. INFO = ', info End If 99999 Format (1X,A,I2,A,1P,E11.4) 99998 Format (1X,A,I2,A,'(',1P,E11.4,',',1P,E11.4,')') 99997 Format (1X,A,I2,A) 99996 Format (1X,1P,E11.4) 99995 Format (1X,'(',1P,E11.4,',',1P,E11.4,')') 99994 Format (1X,A,I4) End Program f08nafe