PROGRAM f07mafe ! F07MAF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dsysv, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nb = 64, nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, lda, lwork, n ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: a(:,:), b(:), work(:) INTEGER, ALLOCATABLE :: ipiv(:) ! .. Executable Statements .. WRITE (nout,*) 'F07MAF Example Program Results' WRITE (nout,*) ! Skip heading in data file READ (nin,*) READ (nin,*) n lda = n lwork = nb*n ALLOCATE (a(lda,n),b(n),work(lwork),ipiv(n)) ! Read the upper triangular part of the matrix 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 dsysv is f07maf CALL dsysv('Upper',n,1,a,lda,ipiv,b,n,work,lwork,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, & 'Details of the factorization',ifail) ! Print pivot indices WRITE (nout,*) WRITE (nout,*) 'Pivot indices' WRITE (nout,99998) ipiv(1:n) ELSE WRITE (nout,99997) 'The diagonal block ', info, ' of D is zero' END IF 99999 FORMAT ((3X,7F11.4)) 99998 FORMAT (1X,7I11) 99997 FORMAT (1X,A,I3,A) END PROGRAM f07mafe