/* nag_dorghr (f08nfc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. * Mark 7b revised, 2004. */ #include #include #include #include #include #include #include #include int main(void) { /* Scalars */ double norm, alpha, beta; Integer i, j, n, pda, pdc, pdd, pdz, tau_len, wi_len; Integer exit_status = 0; NagError fail; Nag_OrderType order; /* Arrays */ double *a = 0, *c = 0, *d = 0, *tau = 0, *wi = 0, *wr = 0, *z = 0; #ifdef NAG_COLUMN_MAJOR #define A(I, J) a[(J - 1) * pda + I - 1] #define D(I, J) d[(J - 1) * pdd + I - 1] #define Z(I, J) z[(J - 1) * pdz + I - 1] order = Nag_ColMajor; #else #define A(I, J) a[(I - 1) * pda + J - 1] #define D(I, J) d[(I - 1) * pdd + J - 1] #define Z(I, J) z[(I - 1) * pdz + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dorghr (f08nfc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%*[^\n] ", &n); pda = n; pdc = n; pdd = n; pdz = n; tau_len = n - 1; wi_len = n; /* Allocate memory */ if (!(a = NAG_ALLOC(n * n, double)) || !(c = NAG_ALLOC(n * n, double)) || !(d = NAG_ALLOC(n * n, double)) || !(tau = NAG_ALLOC(tau_len, double)) || !(wi = NAG_ALLOC(wi_len, double)) || !(wr = NAG_ALLOC(wi_len, double)) || !(z = NAG_ALLOC(n * n, 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] "); /* Copy A into D */ for (i = 1; i <= n; ++i) { for (j = 1; j <= n; ++j) D(i, j) = A(i, j); } /* nag_gen_real_mat_print (x04cac): Print Matrix A. */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n, a, pda, "Matrix A", 0, &fail); printf("\n"); if (fail.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_dgehrd (f08nec): Reduce A to upper Hessenberg form H = (Q**T)*A*Q */ 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; } /* Copy A into Z */ for (i = 1; i <= n; ++i) { for (j = 1; j <= n; ++j) Z(i, j) = A(i, j); } /* nag_dorghr (f08nfc): Form Q explicitly, storing the result in Z */ nag_dorghr(order, n, 1, n, z, pdz, tau, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dorghr (f08nfc).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_dhseqr (f08pec): * Calculate the Schur factorization of H = Y*T*(Y**T) and form * Z=Q*Y explicitly. Note that A = Z*T*(Z**T). */ nag_dhseqr(order, Nag_Schur, Nag_UpdateZ, n, 1, n, a, pda, wr, wi, z, pdz, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dhseqr (f08pec).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_dgemm (f16yac): Compute A - Z*T*Z^T from the factorization of */ /* A and store in matrix D*/ alpha = 1.0; beta = 0.0; nag_dgemm(order, Nag_NoTrans, Nag_NoTrans, n, n, n, alpha, z, pdz, a, pda, beta, c, pdc, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgemm (f16yac).\n%s\n", fail.message); exit_status = 1; goto END; } alpha = -1.0; beta = 1.0; nag_dgemm(order, Nag_NoTrans, Nag_Trans, n, n, n, alpha, c, pdc, z, pdz, beta, d, pdd, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dgemm (f16yac).\n%s\n", fail.message); exit_status = 1; goto END; } /* nag_dge_norm (f16rac): Find norm of matrix D and print warning if */ /* it is too large */ nag_dge_norm(order, Nag_OneNorm, n, n, d, pdd, &norm, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dge_norm (f16rac).\n%s\n", fail.message); exit_status = 1; goto END; } if (norm>pow(x02ajc(),0.8)) { printf("%s\n%s\n","Norm of A-(Z*T*Z^T) is much greater than 0.", "Schur factorization has failed."); } END: if (a) NAG_FREE(a); if (c) NAG_FREE(c); if (d) NAG_FREE(d); if (tau) NAG_FREE(tau); if (wi) NAG_FREE(wi); if (wr) NAG_FREE(wr); if (z) NAG_FREE(z); return exit_status; } #undef A #undef D #undef Z