PROGRAM f07gnfe ! F07GNF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : nag_wp, x04ddf, zppsv ! .. 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 .. COMPLEX (KIND=nag_wp), ALLOCATABLE :: ap(:), b(:) CHARACTER (1) :: clabs(1), rlabs(1) ! .. Executable Statements .. WRITE (nout,*) 'F07GNF 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 zppsv is f07gnf CALL zppsv(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 x04ddf(uplo,'Non-unit diagonal',n,ap,'Bracketed','F7.4', & 'Cholesky factor','Integer',rlabs,'Integer',clabs,80,0,ifail) ELSE WRITE (nout,99998) 'The leading minor of order ', info, & ' is not positive definite' END IF 99999 FORMAT ((3X,4(' (',F7.4,',',F7.4,')':))) 99998 FORMAT (1X,A,I3,A) END PROGRAM f07gnfe