/* nag_real_symm_eigensystem (f02abc) Example Program. * * Copyright 1990 Numerical Algorithms Group. * * Mark 2 revised, 1992. * Mark 8 revised, 2004. */ #include #include #include #include #define A(I, J) a[(I) *tda + J] #define V(I, J) v[(I) *tdv + J] int main(void) { Integer exit_status = 0, i, j, n, tda, tdv; NagError fail; double *a = 0, *r = 0, *v = 0; INIT_FAIL(fail); printf( "nag_real_symm_eigensystem (f02abc) Example Program Results\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld", &n); if (n >= 1) { if (!(a = NAG_ALLOC(n*n, double)) || !(r = NAG_ALLOC(n, double)) || !(v = NAG_ALLOC(n*n, double))) { printf("Allocation failure\n"); exit_status = -1; goto END; } tda = n; tdv = n; } else { printf("Invalid n.\n"); exit_status = 1; return exit_status; } for (i = 0; i < n; i++) for (j = 0; j < n; j++) scanf("%lf", &A(i, j)); /* nag_real_symm_eigensystem (f02abc). * All eigenvalues and eigenvectors of real symmetric matrix */ nag_real_symm_eigensystem(n, a, tda, r, v, tdv, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_real_symm_eigensystem (f02abc).\n%s\n", fail.message); exit_status = 1; goto END; } printf("Eigenvalues\n"); for (i = 0; i < n; i++) printf("%9.4f%s", r[i], (i%8 == 7 || i == n-1)?"\n":" "); printf("Eigenvectors\n"); for (i = 0; i < n; i++) for (j = 0; j < n; j++) printf("%9.4f%s", V(i, j), (j%8 == 7 || j == n-1)?"\n":" "); END: if (a) NAG_FREE(a); if (r) NAG_FREE(r); if (v) NAG_FREE(v); return exit_status; }