Program dposv_example ! DPOSV Example Program Text ! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com ! .. Use Statements .. Use lapack_example_aux, Only: nagf_file_print_matrix_real_gen Use lapack_interfaces, Only: dposv Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, lda, n ! .. Local Arrays .. Real (Kind=dp), Allocatable :: a(:, :), b(:) ! .. Executable Statements .. Write (nout, *) 'DPOSV Example Program Results' Write (nout, *) ! Skip heading in data file Read (nin, *) Read (nin, *) n lda = n Allocate (a(lda,n), b(n)) ! Read the upper triangular part of 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 Call dposv('Upper', n, 1, a, lda, b, n, info) If (info==0) Then ! Print solution Write (nout, *) 'Solution' Write (nout, 100) 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 nagf_file_print_matrix_real_gen('Upper', 'Non-unit diagonal', n, & n, a, lda, 'Cholesky factor U', ifail) Else Write (nout, 110) 'The leading minor of order ', info, & ' is not positive definite' End If 100 Format ((3X,7F11.4)) 110 Format (1X, A, I3, A) End Program