/* nag_dormtr (f08fgc) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include int main(void) { /* Scalars */ Integer i, j, m, n, nsplit, pda, pdz, d_len, e_len, tau_len; Integer exit_status=0; double vl=0.0, vu=0.0; NagError fail; Nag_UploType uplo; Nag_OrderType order; /* Arrays */ char uplo_char[2]; Integer *iblock=0, *ifailv=0, *isplit=0; double *a=0, *d=0, *e=0, *tau=0, *w=0, *z=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); Vprintf("nag_dormtr (f08fgc) Example Program Results\n\n"); /* Skip heading in data file */ Vscanf("%*[^\n] "); Vscanf("%ld%*[^\n] ", &n); pda = n; pdz = n; tau_len = n-1; d_len = n; e_len = n-1; /* Allocate memory */ if ( !(a = NAG_ALLOC(n * n, double)) || !(d = NAG_ALLOC(d_len, double)) || !(e = NAG_ALLOC(e_len, double)) || !(iblock = NAG_ALLOC(n, Integer)) || !(ifailv = NAG_ALLOC(n, Integer)) || !(isplit = NAG_ALLOC(n, Integer)) || !(w = NAG_ALLOC(n, double)) || !(tau = NAG_ALLOC(tau_len, double)) || !(z = NAG_ALLOC(n * n, double)) ) { Vprintf("Allocation failure\n"); exit_status = -1; goto END; } /* Read A from data file */ Vscanf(" ' %1s '%*[^\n] ", uplo_char); if (*(unsigned char *)uplo_char == 'L') uplo = Nag_Lower; else if (*(unsigned char *)uplo_char == 'U') uplo = Nag_Upper; else { Vprintf("Unrecognised character for Nag_UploType type\n"); exit_status = -1; goto END; } if (uplo == Nag_Upper) { for (i = 1; i <= n; ++i) { for (j = i; j <= n; ++j) Vscanf("%lf", &A(i,j)); } Vscanf("%*[^\n] "); } else { for (i = 1; i <= n; ++i) { for (j = 1; j <= i; ++j) Vscanf("%lf", &A(i,j)); } Vscanf("%*[^\n] "); } /* Reduce A to tridiagonal form T = (Q**T)*A*Q */ /* nag_dsytrd (f08fec). * Orthogonal reduction of real symmetric matrix to * symmetric tridiagonal form */ nag_dsytrd(order, uplo, n, a, pda, d, e, tau, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_dsytrd (f08fec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Calculate the two smallest eigenvalues of T (same as A) */ /* nag_dstebz (f08jjc). * Selected eigenvalues of real symmetric tridiagonal matrix * by bisection */ nag_dstebz(Nag_Indices, Nag_ByBlock, n, vl, vu, 1, 2, 0.0, d, e, &m, &nsplit, w, iblock, isplit, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_dstebz (f08jjc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print eigenvalues */ Vprintf("Eigenvalues\n"); for (i = 0; i < m; ++i) Vprintf("%8.4f%s", w[i], (i+1)%8==0 ?"\n":" "); Vprintf("\n\n"); /* Calculate the eigenvectors of T storing the result in Z */ /* nag_dstein (f08jkc). * Selected eigenvectors of real symmetric tridiagonal * matrix by inverse iteration, storing eigenvectors in real * array */ nag_dstein(order, n, d, e, m, w, iblock, isplit, z, pdz, ifailv, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_dstein (f08jkc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Calculate all the eigenvectors of A = Q*(eigenvectors of T) */ /* nag_dormtr (f08fgc). * Apply orthogonal transformation determined by nag_dsytrd * (f08fec) */ nag_dormtr(order, Nag_LeftSide, uplo, Nag_NoTrans, n, m, a, pda, tau, z, pdz, &fail); if (fail.code != NE_NOERROR) { Vprintf("Error from nag_dormtr (f08fgc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print eigenvectors */ /* nag_gen_real_mat_print (x04cac). * Print real general matrix (easy-to-use) */ nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz, "Eigenvectors", 0, &fail); if (fail.code != NE_NOERROR) { Vprintf("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 (d) NAG_FREE(d); if (e) NAG_FREE(e); if (iblock) NAG_FREE(iblock); if (ifailv) NAG_FREE(ifailv); if (isplit) NAG_FREE(isplit); if (tau) NAG_FREE(tau); if (w) NAG_FREE(w); if (z) NAG_FREE(z); return exit_status; }