Stopping Condition Dilemma: ODE Integration with C++ and Boost Library

Question

I am currently working on solving an ordinary differential equation (ODE) using C++ and the Boost library. The specific form of the ODE is dp/dt = (...) with an initial condition of p(0) = pmax. The task at hand is to design an integrator that halts when the condition p(r) <= p_min is met. However, the challenge lies in the fact that I don't have prior knowledge of the exact value for end_time, as the integrator receives input values such as "start_time," "end_time," and "dt."