for (int i = 0; i < size_; ++i) {
for (int j = 0; j <= i; ++j) {
final Var_Helper helper = new Var_Helper(this, i, j);
final GaussKronrodAdaptive integrator = new GaussKronrodAdaptive(1e-10, 10000);
for(int k = 0; k<64; ++k) {
tmp.set(i, j, tmp.get(i, j)+integrator.op(helper, k*t/64.0,(k+1)*t/64.0));
}
tmp.set(j,i, tmp.get(i, j));
}
}