Program f08upfe ! F08UPF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x04daf, zhbgvx ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Real (Kind=nag_wp), Parameter :: zero = 0.0E+0_nag_wp Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: uplo = 'U' ! .. Local Scalars .. Real (Kind=nag_wp) :: abstol, vl, vu Integer :: i, ifail, il, info, iu, j, ka, kb, & ldab, ldbb, ldq, ldz, m, n ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: ab(:,:), bb(:,:), q(:,:), work(:), & z(:,:) Real (Kind=nag_wp), Allocatable :: rwork(:), w(:) Integer, Allocatable :: iwork(:), jfail(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F08UPF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n, ka, kb ldab = ka + 1 ldbb = kb + 1 ldq = n ldz = n m = n Allocate (ab(ldab,n),bb(ldbb,n),q(ldq,n),work(n),z(ldz,m),rwork(7*n), & w(n),iwork(5*n),jfail(n)) ! Read the lower and upper bounds of the interval to be searched, ! and read the upper or lower triangular parts of the matrices A ! and B from data file Read (nin,*) vl, vu If (uplo=='U') Then Read (nin,*)((ab(ka+1+i-j,j),j=i,min(n,i+ka)),i=1,n) Read (nin,*)((bb(kb+1+i-j,j),j=i,min(n,i+kb)),i=1,n) Else If (uplo=='L') Then Read (nin,*)((ab(1+i-j,j),j=max(1,i-ka),i),i=1,n) Read (nin,*)((bb(1+i-j,j),j=max(1,i-kb),i),i=1,n) End If ! Set the absolute error tolerance for eigenvalues. With abstol ! set to zero, the default value is used instead abstol = zero ! Solve the generalized symmetric eigenvalue problem ! A*x = lambda*B*x ! The NAG name equivalent of zhbgvx is f08upf Call zhbgvx('Vectors','Values in range',uplo,n,ka,kb,ab,ldab,bb,ldbb,q, & ldq,vl,vu,il,iu,abstol,m,w,z,ldz,work,rwork,iwork,jfail,info) If (info>=0 .And. info<=n) Then ! Print solution Write (nout,99999) 'Number of eigenvalues found =', m Write (nout,*) Write (nout,*) 'Eigenvalues' Write (nout,99998) w(1:m) Flush (nout) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04daf('General',' ',n,m,z,ldz,'Selected eigenvectors',ifail) If (info>0) Then Write (nout,99999) 'INFO eigenvectors failed to converge, INFO =', & info Write (nout,*) 'Indices of eigenvectors that did not converge' Write (nout,99997) jfail(1:m) End If Else If (info>n .And. info<=2*n) Then i = info - n Write (nout,99996) 'The leading minor of order ', i, & ' of B is not positive definite' Else Write (nout,99999) 'Failure in ZHBGVX. INFO =', info End If 99999 Format (1X,A,I5) 99998 Format (3X,(8F8.4)) 99997 Format (3X,(8I8)) 99996 Format (1X,A,I4,A) End Program f08upfe