Program f07gvfe ! F07GVF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: nag_wp, x04dbf, zpprfs, zpptrf, zpptrs ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: aplen, i, ifail, info, j, ldb, ldx, & n, nrhs Character (1) :: uplo ! .. Local Arrays .. Complex (Kind=nag_wp), Allocatable :: afp(:), ap(:), b(:,:), work(:), & x(:,:) Real (Kind=nag_wp), Allocatable :: berr(:), ferr(:), rwork(:) Character (1) :: clabs(1), rlabs(1) ! .. Executable Statements .. Write (nout,*) 'F07GVF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs ldb = n ldx = n aplen = n*(n+1)/2 Allocate (afp(aplen),ap(aplen),b(ldb,nrhs),work(2*n),x(ldx,n), & berr(nrhs),ferr(nrhs),rwork(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:aplen) = ap(1:aplen) x(1:n,1:nrhs) = b(1:n,1:nrhs) ! Factorize A in the array AFP ! The NAG name equivalent of zpptrf is f07grf Call zpptrf(uplo,n,afp,info) Write (nout,*) Flush (nout) If (info==0) Then ! Compute solution in the array X ! The NAG name equivalent of zpptrs is f07gsf Call zpptrs(uplo,n,nrhs,afp,x,ldx,info) ! Improve solution, and compute backward errors and ! estimated bounds on the forward errors ! The NAG name equivalent of zpprfs is f07gvf Call zpprfs(uplo,n,nrhs,ap,afp,b,ldb,x,ldx,ferr,berr,work,rwork,info) ! Print solution ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04dbf('General',' ',n,nrhs,x,ldx,'Bracketed','F7.4', & 'Solution(s)','Integer',rlabs,'Integer',clabs,80,0,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,*) 'A is not positive definite' End If 99999 Format ((5X,1P,4(E11.1,7X))) End Program f07gvfe