PROGRAM f07phfe ! F07PHF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dsprfs, dsptrf, dsptrs, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, j, ldb, ldx, len, n, & nrhs CHARACTER (1) :: uplo ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: afp(:), ap(:), b(:,:), berr(:), & ferr(:), work(:), x(:,:) INTEGER, ALLOCATABLE :: ipiv(:), iwork(:) ! .. Executable Statements .. WRITE (nout,*) 'F07PHF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n, nrhs ldb = n ldx = n len = n*(n+1)/2 ALLOCATE (afp(len),ap(len),b(ldb,nrhs),berr(nrhs),ferr(nrhs),work(3*n), & x(ldx,n),ipiv(n),iwork(n)) ! Read A and B from data file, and copy A to AFP and B to X READ (nin,*) uplo 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 (nin,*) (b(i,1:nrhs),i=1,n) afp(1:len) = ap(1:len) x(1:n,1:nrhs) = b(1:n,1:nrhs) ! Factorize A in the array AFP ! The NAG name equivalent of dsptrf is f07pdf CALL dsptrf(uplo,n,afp,ipiv,info) WRITE (nout,*) FLUSH (nout) IF (info==0) THEN ! Compute solution in the array X ! The NAG name equivalent of dsptrs is f07pef CALL dsptrs(uplo,n,nrhs,afp,ipiv,x,ldx,info) ! Improve solution, and compute backward errors and ! estimated bounds on the forward errors ! The NAG name equivalent of dsprfs is f07phf CALL dsprfs(uplo,n,nrhs,ap,afp,ipiv,b,ldb,x,ldx,ferr,berr,work, & iwork,info) ! Print solution ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 CALL x04caf('General',' ',n,nrhs,x,ldx,'Solution(s)',ifail) WRITE (nout,*) WRITE (nout,*) 'Backward errors (machine-dependent)' WRITE (nout,99999) berr(1:nrhs) WRITE (nout,*) 'Estimated forward error bounds (machine-dependent)' WRITE (nout,99999) ferr(1:nrhs) ELSE WRITE (nout,*) 'The factor D is singular' END IF 99999 FORMAT ((3X,1P,7E11.1)) END PROGRAM f07phfe