Program f07gafe ! F07GAF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dppsv, nag_wp, x04ccf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: uplo = 'U' ! .. Local Scalars .. Integer :: i, ifail, info, j, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ap(:), b(:) ! .. Executable Statements .. Write (nout,*) 'F07GAF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n Allocate (ap((n*(n+1))/2),b(n)) ! Read the upper or lower triangular part of the matrix A from ! data file If (uplo=='U') Then Read (nin,*)((ap(i+(j*(j-1))/2),j=i,n),i=1,n) Else If (uplo=='L') Then Read (nin,*)((ap(i+((2*n-j)*(j-1))/2),j=1,i),i=1,n) End If ! Read b from data file Read (nin,*) b(1:n) ! Solve the equations Ax = b for x ! The NAG name equivalent of dppsv is f07gaf Call dppsv(uplo,n,1,ap,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 x04ccf(uplo,'Non-unit diagonal',n,ap,'Cholesky factor',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 f07gafe