Program f04chfe ! F04CHF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: f04chf, nag_wp, x04dbf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: errbnd, rcond Integer :: i, ierr, ifail, lda, ldb, n, nrhs ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: a(:,:), b(:,:) Integer, Allocatable :: ipiv(:) Character (1) :: clabs(1), rlabs(1) ! .. Executable Statements .. Write (nout,*) 'F04CHF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs lda = n ldb = n Allocate (a(lda,n),b(ldb,nrhs),ipiv(n)) ! Read the upper triangular part of A from data file Read (nin,*)(a(i,i:n),i=1,n) ! Read B from data file Read (nin,*)(b(i,1:nrhs),i=1,n) ! Solve the equations AX = B for X ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 1 Call f04chf('Upper',n,nrhs,a,lda,ipiv,b,ldb,rcond,errbnd,ifail) If (ifail==0) Then ! Print solution, estimate of condition number and approximate ! error bound ierr = 0 Call x04dbf('General',' ',n,nrhs,b,ldb,'Bracketed',' ','Solution', & 'Integer',rlabs,'Integer',clabs,80,0,ierr) Write (nout,*) Write (nout,*) 'Estimate of condition number' Write (nout,99999) 1.0E0_nag_wp/rcond Write (nout,*) Write (nout,*) 'Estimate of error bound for computed solutions' Write (nout,99999) errbnd Else If (ifail==n+1) Then ! Matrix A is numerically singular. Print estimate of ! reciprocal of condition number and solution Write (nout,*) Write (nout,*) 'Estimate of reciprocal of condition number' Write (nout,99999) rcond Write (nout,*) Flush (nout) ierr = 0 Call x04dbf('General',' ',n,nrhs,b,ldb,'Bracketed',' ','Solution', & 'Integer',rlabs,'Integer',clabs,80,0,ierr) Else If (ifail>0 .And. ifail<=n) Then ! The upper triangular matrix U is exactly singular. Print ! details of factorization Write (nout,*) Flush (nout) ierr = 0 Call x04dbf('Upper','Non-unit diagonal',n,n,a,lda,'Bracketed',' ', & 'Details of factorization','Integer',rlabs,'Integer',clabs,80,0, & ierr) ! Print pivot indices Write (nout,*) Write (nout,*) 'Pivot indices' Write (nout,99998) ipiv(1:n) Else Write (nout,99997) ifail End If 99999 Format (8X,1P,E9.1) 99998 Format ((1X,7I11)) 99997 Format (1X,' ** F04CHF returned with IFAIL = ',I5) End Program f04chfe