/* nag_dsteqr (f08jec) Example Program. * * Copyright 2001 Numerical Algorithms Group. * * Mark 7, 2001. */ #include #include #include #include #include #include int main(void) { /* Scalars */ Integer i, j, k, n, pdz, d_len, e_len, rowinc; Integer exit_status = 0; double r; /* Arrays */ double *z = 0, *d = 0, *e = 0; /* Nag Types */ NagError fail; Nag_OrderType order; #ifdef NAG_COLUMN_MAJOR #define Z(I, J) z[(J - 1) * pdz + I - 1] order = Nag_ColMajor; #else #define Z(I, J) z[(I - 1) * pdz + J - 1] order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dsteqr (f08jec) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n] "); scanf("%ld%*[^\n] ", &n); #ifdef NAG_COLUMN_MAJOR rowinc = 1; #else rowinc = n; #endif pdz = n; d_len = n; e_len = n - 1; /* Allocate memory */ if (!(z = NAG_ALLOC(n * n, double)) || !(d = NAG_ALLOC(d_len, double)) || !(e = NAG_ALLOC(e_len, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read T from data file */ for (i = 0; i < d_len; ++i) scanf("%lf", &d[i]); for (i = 0; i < e_len; ++i) scanf("%lf", &e[i]); /* Calculate all the eigenvalues and eigenvectors of tridiagonal matrix T, * reduced from real symmetric matrix using nag_dsteqr (f08jec). */ nag_dsteqr(order, Nag_InitZ, n, d, e, z, pdz, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dsteqr (f08jec).\n%s\n", fail.message); exit_status = 1; goto END; } /* Normalize the eigenvectors */ for(j=1; j<=n; j++) { nag_damax_val(n, &Z(1,j), rowinc, &k, &r, &fail); for (i=1; i<=n; i++) Z(i,j) = Z(i,j)/r; } /* Print eigenvalues and eigenvectors */ printf(" Eigenvalues\n"); for (i = 0; i < n; ++i) printf(" %7.4lf", d[i]); printf("\n\n"); /* Print real general matrix Z using easy-to-use * nag_gen_real_mat_print (x04cac). */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n, z, pdz, "Eigenvectors", 0, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message); exit_status = 1; } END: NAG_FREE(d); NAG_FREE(e); NAG_FREE(z); return exit_status; }