/* nag_dgehrd (f08nec) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include int main(void) { /* Scalars */ Integer i, j, n, pda, tau_len; Integer exit_status = 0; NagError fail; Nag_OrderType order; /* Arrays */ double *a = 0, *tau = 0; #ifdef NAG_COLUMN_MAJOR #define A(I, J) a[(J - 1) * pda + I - 1] order = Nag_ColMajor; #else #define A(I, J) a[(I - 1) * pda + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dgehrd (f08nec) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%*[^\n] ", &n); pda = n; tau_len = n - 1; /* Allocate memory */ if (!(a = NAG_ALLOC(n * n, double)) || !(tau = NAG_ALLOC(tau_len, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ for (i = 1; i <= n; ++i) { for (j = 1; j <= n; ++j) scanf("%lf", &A(i, j)); } scanf("%*[^\n] "); /* nag_dgehrd (f08nec): Reduce A to upper Hessenberg form */ nag_dgehrd(order, n, 1, n, a, pda, tau, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgehrd (f08nec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Set the elements below the first sub-diagonal to zero */ for (i = 1; i <= n - 2; ++i) { for (j = i + 2; j <= n; ++j) A(j, i) = 0.0; } /* nag_gen_real_mat_print (x04cac): Print upper Hessenberg form. */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n, a, pda, "Upper Hessenberg form", 0, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; goto END; } END: if (a) NAG_FREE(a); if (tau) NAG_FREE(tau); return exit_status; } #undef A