Program f07hafe ! F07HAF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dpbsv, nag_wp, x04cef ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: uplo = 'U' ! .. Local Scalars .. Integer :: i, ifail, info, j, kd, ldab, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), b(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F07HAF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) Read (nin,*) n, kd ldab = kd + 1 Allocate (ab(ldab,n),b(n)) ! Read the upper or lower triangular part of the band matrix A ! from data file If (uplo=='U') Then Read (nin,*)((ab(kd+1+i-j,j),j=i,min(n,i+kd)),i=1,n) Else If (uplo=='L') Then Read (nin,*)((ab(1+i-j,j),j=max(1,i-kd),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 dpbsv is f07haf Call dpbsv(uplo,n,kd,1,ab,ldab,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 If (uplo=='U') Then Call x04cef(n,n,0,kd,ab,ldab,'Cholesky factor U',ifail) Else If (uplo=='L') Then Call x04cef(n,n,kd,0,ab,ldab,'Cholesky factor L',ifail) End If 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 f07hafe