/* nag_dstevr (f08jdc) Example Program. * * Copyright 2011 Numerical Algorithms Group. * * Mark 23, 2011. */ #include #include #include #include #include int main(void) { /* Scalars */ double abstol, vl = 0.0, vu = 0.0; Integer exit_status = 0, i, il, iu, j, m, n, pdz; /* Arrays */ double *d = 0, *e = 0, *w = 0, *z = 0; Integer *isuppz = 0; /* Nag Types */ Nag_OrderType order; NagError fail; #ifdef NAG_COLUMN_MAJOR order = Nag_ColMajor; #else order = Nag_RowMajor; #endif INIT_FAIL(fail); printf("nag_dstevr (f08jdc) Example Program Results\n\n"); /* Skip heading in data file and read n and the lower and upper * indices of the eigenvalues to be found. */ scanf("%*[^\n]"); scanf("%ld%ld%ld%*[^\n]", &n, &il, &iu); m = iu - il +1; pdz = n; /* Allocate memory */ if (!(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n-1, double)) || !(w = NAG_ALLOC(n, double)) || !(z = NAG_ALLOC(n * n, double)) || !(isuppz = NAG_ALLOC(n, Integer))) { printf("Allocation failure\n"); exit_status = -1; goto END; } /* Read the diagonal and off-diagonal elements of the matrix A * from data file. */ 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]"); /* Set the absolute error tolerance for eigenvalues. * With abstol set to zero, the default value is used instead. */ abstol = 0.0; /* nag_dstevr (f08jdc). * Solve the symmetric tridiagonal eigenvalue problem. */ nag_dstevr(order, Nag_DoBoth, Nag_Indices, n, d, e, vl, vu, il, iu, abstol, &m, w, z, pdz, isuppz, &fail); if (fail.code != NE_NOERROR) { printf("Error from nag_dstevr (f08jdc).\n%s\n", fail.message); exit_status = 1; goto END; } /* Print solution */ printf("Selected eigenvalues\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. */ fflush(stdout); nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z, pdz, "Selected 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; goto END; } END: if (d) NAG_FREE(d); if (e) NAG_FREE(e); if (w) NAG_FREE(w); if (z) NAG_FREE(z); if (isuppz) NAG_FREE(isuppz); return exit_status; }