/* nag_dstevx (f08jbc) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include #include int main(void) { /* Scalars */ double abstol, vl, vu; Integer exit_status = 0, i, il = 0, iu = 0, j, m, n, pdz; /* Arrays */ double *d = 0, *e = 0, *w = 0, *z = 0; Integer *index = 0; /* Nag Types */ Nag_OrderType order; NagError fail, fail_print; #ifdef NAG_COLUMN_MAJOR order = Nag_ColMajor; #else order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dstevx (f08jbc) Example Program Results\n\n"); /* Skip heading in data file */ scanf("%*[^\n]"); scanf("%ld%*[^\n]", &n); pdz = n; /* Allocate memory */ if (!(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n, double)) || !(w = NAG_ALLOC(n, double)) || !(z = NAG_ALLOC(pdz * n, double)) || !(index = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the lower and upper bounds of the interval to be searched, * and read the diagonal and off-diagonal elements of the matrix * A from data file. */ scanf("%lf%lf%*[^\n]", &vl, &vu); for (i = 0; i < n; ++i) scanf("%lf", &d[i]); scanf("%*[^\n]"); for (i = 0; i < n - 1; ++i) scanf("%lf", &e[i]); scanf("%*[^\n]"); /* nag_real_safe_small_number (X02AMC). * Set the absolute error tolerance for eigenvalues. With abstol * set to zero, the default value would be used instead. */ abstol = nag_real_safe_small_number * 2; /* nag_dstevx (f08jbc). * Solve the symmetric eigenvalue problem. */ nag_dstevx(order, Nag_DoBoth, Nag_Interval, n, d, e, vl, vu, il, iu, abstol, &m, w, z, pdz, index, &fail); if (fail.code != NE_NOERROR && fail.code != NE_CONVERGENCE) { printf("Error from nag_dstevx (f08jbc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print solution */ printf("Number of eigenvalues found =%5ld\n", m); printf("\nEigenvalues\n"); for (j = 0; j < m; ++j) printf("%8.4f%s", w[j], (j+1)%8 == 0?"\n":" "); printf("\n\n"); /* nag_gen_real_mat_print (x04cac). * Print selected eigenvectors. */ INIT_FAIL(fail_print); fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz, "Selected eigenvectors", 0, &fail_print); if (fail_print.code != NE_NOERROR) { printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail_print.message); exit_status = 1; goto END; } if (fail.code == NE_CONVERGENCE) { printf("eigenvectors failed to converge\n"); printf("Indices of eigenvectors that did not converge\n"); for (j = 0; j < m; ++j) printf("%8ld%s", index[j], (j+1)%8 == 0?"\n":" "); printf("\n"); } END: if (d) NAG_FREE(d); if (e) NAG_FREE(e); if (w) NAG_FREE(w); if (z) NAG_FREE(z); if (index) NAG_FREE(index); return exit_status; }