  Simulating chemical reaction networks is often computationally demanding, in
particular due to stiffness. We propose a novel simulation scheme where long
runs are not simulated as a whole but assembled from shorter precomputed
segments of simulation runs. On the one hand, this speeds up the simulation
process to obtain multiple runs since we can reuse the segments. On the other
hand, questions on diversity and genuineness of our runs arise. However, we
ensure that we generate runs close to their true distribution by generating an
appropriate abstraction of the original system and utilizing it in the
simulation process. Interestingly, as a by-product, we also obtain a yet more
efficient simulation scheme, yielding runs over the system's abstraction. These
provide a very faithful approximation of concrete runs on the desired level of
granularity, at a low cost. Our experiments demonstrate the speedups in the
simulations while preserving key dynamical as well as quantitative properties.
