In this work, we present preliminary results highlighting the effects of collisional fragmentation on the dynamical evolution of two unique planetary systems: the inner Solar System during the late stage of terrestrial planet formation, and a giant-impact generated debris disk around Mars out of which the martian moons, Phobos and Deimos, could form. This work is conducted using an updated version of the N-body dynamics code Swifter-SyMBA developed by our group that contains upgrades aimed at improving the performance in a shared-memory parallel computing environment, which we have dubbed "Swiftest." Recent developments highlighting the importance of collisional outcomes in determining the mass, orbital elements, and accretion timescale of the growing terrestrial planets have prompted the development of the upgraded Swiftest code. Swiftest includes the following major updates to the Swifter code: (1) the incorporation of collisional fragmentation characterized by collisional regimes, as discussed in this work, and (2) improvements to the internal data structures and optimizations aimed at improving performance to support collisional fragmentation, while minimizing changes to the core SyMBA algorithm. Preliminary results of our model of the accretion of the Solar System with Swiftest show that the inclusion of collisional fragmentation increases the timescale of terrestrial planet accretion, which is consistent with previously published results. The increased lifetime of the late stage accretion phase results in an increase in collisional debris in the inner solar system, which could have potential consequences for the cratering histories of the terrestrial planets. Preliminary results for the martian system demonstrate that the inclusion of collisional fragmentation and collisional regimes increases the timescale of accretion in the martian debris disk. In particular, the types of collisions that occur during accretion are highly dependent on the initial state of the debris disk.