Program f02jqfe
! F02JQF Example Program Text
! Mark 30.0 Release. NAG Copyright 2024.
! .. Use Statements ..
Use nag_library, Only: f02jqf, m01def, m01edf, nag_wp, x04caf, x04daf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Real (Kind=nag_wp), Parameter :: tol = 0.0E0_nag_wp
Real (Kind=nag_wp), Parameter :: zero = 0.0E+0_nag_wp
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Real (Kind=nag_wp) :: t0, t1
Integer :: i, ifail, iwarn, j, lda, ldb, ldc, &
ldvl, ldvr, n, scal, sense, tdvl, &
tdvr
Character (1) :: jobvl, jobvr
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:,:), alpha(:), b(:,:), beta(:), &
c(:,:), cvr(:), e(:), vl(:,:), &
vr(:,:)
Real (Kind=nag_wp), Allocatable :: bevl(:), bevr(:), ea(:,:), s(:)
Integer, Allocatable :: irank(:)
! .. Intrinsic Procedures ..
Intrinsic :: abs, all, maxval, real
! .. Executable Statements ..
Write (nout,*) 'F02JQF Example Program Results'
Flush (nout)
! Skip heading in data file and read in n, scal, sense, jobVL and jobVR
Read (nin,*)
Read (nin,*) n, scal, sense
Read (nin,*) jobvl, jobvr
lda = n
ldb = n
ldc = n
ldvl = n
ldvr = n
tdvl = 2*n
tdvr = 2*n
Allocate (a(lda,n),b(ldb,n),c(ldc,n),alpha(2*n),beta(2*n),e(2*n), &
vl(ldvl,tdvl),vr(ldvr,tdvr),s(2*n),bevr(2*n),bevl(2*n),cvr(n), &
ea(2*n,2),irank(2*n))
! Read in the matrices A, B and C
Read (nin,*)(a(i,1:n),i=1,n)
Read (nin,*)(b(i,1:n),i=1,n)
Read (nin,*)(c(i,1:n),i=1,n)
! Solve the quadratic eigenvalue problem
ifail = -1
Call f02jqf(scal,jobvl,jobvr,sense,tol,n,a,lda,b,ldb,c,ldc,alpha,beta, &
vl,ldvl,vr,ldvr,s,bevl,bevr,iwarn,ifail)
If (iwarn/=0) Then
Write (nout,*)
Write (nout,99999) 'Warning from f02jqf. IWARN =', iwarn
End If
Write (nout,*)
If (ifail/=0) Then
Write (nout,99999) 'Failure in f02jqf. IFAIL =', ifail
Go To 100
End If
Flush (nout)
If (all(real(beta(1:2*n))>zero)) Then
e(1:2*n) = alpha(1:2*n)/beta(1:2*n)
! Sort eigenvalues by absolute value and then by real part.
! Add 1000.0 to tie differences of small orders of epsilon.
ea(1:2*n,1) = 1000.0_nag_wp + abs(e(1:2*n))
ea(1:2*n,2) = real(e(1:2*n))
ifail = 0
Call m01def(ea,2*n,1,2*n,1,2,'Descending',irank,ifail)
Call m01edf(e,1,2*n,irank,ifail)
! Print Eigenvalues
ifail = 0
Call x04daf('General',' ',1,2*n,e,1,'Eigenvalues:',ifail)
If (jobvr=='V' .Or. jobvr=='v') Then
! Sort right eigenvectors using irank
Do j = 1, n
e(1:2*n) = vr(j,1:2*n)
Call m01edf(e,1,2*n,irank,ifail)
vr(j,1:2*n) = e(1:2*n)
End Do
End If
If (jobvl=='V' .Or. jobvl=='v') Then
! Sort left eigenvectors using irank
Do j = 1, n
e(1:2*n) = vl(j,1:2*n)
Call m01edf(e,1,2*n,irank,ifail)
vl(j,1:2*n) = e(1:2*n)
End Do
End If
Else
! Some eigenvalues are infinite
! Print alpha and beta
ifail = 0
Call x04daf('General',' ',1,2*n,alpha,1,'Alpha:',ifail)
ifail = 0
Call x04daf('General',' ',1,2*n,beta,1,'Beta:',ifail)
End If
If (jobvr=='V' .Or. jobvr=='v') Then
! Print Right Eigenvectors
Write (nout,*)
Flush (nout)
ifail = 0
Call x04daf('G',' ',n,2*n,vr,n,'Right Eigenvectors (columns):',ifail)
End If
If (jobvl=='V' .Or. jobvl=='v') Then
! Print Left Eigenvectors
Write (nout,*)
Flush (nout)
ifail = 0
Call x04daf('G',' ',n,2*n,vl,n,'Left Eigenvectors (columns):',ifail)
End If
If (sense==1 .Or. sense>4) Then
Write (nout,*)
Flush (nout)
! Print Eigenvalues
ifail = 0
Call x04caf('G',' ',1,2*n,s,1,'Eigenvalue Condition numbers:',ifail)
End If
If (sense==3 .Or. sense==4 .Or. sense>5) Then
t0 = maxval(bevr)
Write (nout,*)
Write (nout,99998) &
'Max backward error for eigenvalues and right eigenvectors', t0
End If
If (sense==2 .Or. sense==4 .Or. sense==5 .Or. sense==7) Then
t1 = maxval(bevl)
Write (nout,*)
Write (nout,99998) &
'Max backward error for eigenvalues and left eigenvectors ', t1
End If
100 Continue
99999 Format (1X,3(A,I4))
99998 Format (1X,A,1P,E11.1)
End Program f02jqfe