Program zpbrfs_example ! ZPBRFS Example Program Text ! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com ! .. Use Statements .. Use lapack_example_aux, Only: nagf_file_print_matrix_complex_gen_comp Use lapack_interfaces, Only: zpbrfs, zpbtrf, zpbtrs Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Complex (Kind=dp), Parameter :: zero = (0.0E0_dp, 0.0E0_dp) Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, j, kd, ldab, ldafb, ldb, ldx, n, nrhs Character (1) :: uplo ! .. Local Arrays .. Complex (Kind=dp), Allocatable :: ab(:, :), afb(:, :), b(:, :), work(:), & x(:, :) Real (Kind=dp), Allocatable :: berr(:), ferr(:), rwork(:) Character (1) :: clabs(1), rlabs(1) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout, *) 'ZPBRFS Example Program Results' ! Skip heading in data file Read (nin, *) Read (nin, *) n, kd, nrhs ldab = kd + 1 ldafb = kd + 1 ldb = n ldx = n Allocate (ab(ldab,n), afb(ldafb,n), b(ldb,nrhs), work(2*n), x(ldx,n), & berr(nrhs), ferr(nrhs), rwork(n)) ! Set A to zero to avoid referencing uninitialized elements ab(1:kd+1, 1:n) = zero ! Read A and B from data file, and copy A to AFB and B to X Read (nin, *) uplo If (uplo=='U') Then Do i = 1, n Read (nin, *)(ab(kd+1+i-j,j), j=i, min(n,i+kd)) End Do Else If (uplo=='L') Then Do i = 1, n Read (nin, *)(ab(1+i-j,j), j=max(1,i-kd), i) End Do End If Read (nin, *)(b(i,1:nrhs), i=1, n) afb(1:kd+1, 1:n) = ab(1:kd+1, 1:n) x(1:n, 1:nrhs) = b(1:n, 1:nrhs) ! Factorize A in the array AFB Call zpbtrf(uplo, n, kd, afb, ldafb, info) Write (nout, *) Flush (nout) If (info==0) Then ! Compute solution in the array X Call zpbtrs(uplo, n, kd, nrhs, afb, ldafb, x, ldx, info) ! Improve solution, and compute backward errors and ! estimated bounds on the forward errors Call zpbrfs(uplo, n, kd, nrhs, ab, ldab, afb, ldafb, 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 nagf_file_print_matrix_complex_gen_comp('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, 100) berr(1:nrhs) Write (nout, *) 'Estimated forward error bounds (machine-dependent)' Write (nout, 100) ferr(1:nrhs) Else Write (nout, *) 'A is not positive definite' End If 100 Format ((5X,1P,4(E11.1,7X))) End Program