code: public static DoubleMatrix symmetricEigenvalues(DoubleMatrix A) {
          A.assertSquare();
          DoubleMatrix eigenvalues = new DoubleMatrix(A.rows);
          int isuppz[] = new int[2 * A.rows];
          SimpleBlas.syevr('N', 'A', 'U', A.dup(), 0, 0, 0, 0, 0, eigenvalues, dummyDouble, isuppz);
          return eigenvalues;
      }
docs: Compute the eigenvalues for a symmetric matrix.