Program f07fafe ! F07FAF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dposv, nag_wp, x04caf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, lda, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: a(:,:), b(:) ! .. Executable Statements .. Write (nout,*) 'F07FAF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n lda = n Allocate (a(lda,n),b(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(1:n) ! Solve the equations Ax = b for x ! The NAG name equivalent of dposv is f07faf Call dposv('Upper',n,1,a,lda,b,n,info) If (info==0) Then ! Print solution Write (nout,*) 'Solution' Write (nout,99999) b(1:n) ! Print details of factorization Write (nout,*) Flush (nout) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04caf('Upper','Non-unit diagonal',n,n,a,lda,'Cholesky factor U', & ifail) Else Write (nout,99998) 'The leading minor of order ', info, & ' is not positive definite' End If 99999 Format ((3X,7F11.4)) 99998 Format (1X,A,I3,A) End Program f07fafe