Synchronization primitives like barriers heavily impact the performance of parallel programs. As core counts increase and granularity decreases, the value of enabling fast barriers increases. Through the evaluation of the performance of a variety of software implementations of barriers, we found the cost of software barriers to be on the order of tens of thousands of cycles on various incarnations of x64 hardware. We argue that reducing the latency of a barrier via hardware support will dramatically improve the performance of existing applications and runtimes, and would enable new execution models, including those which currently do not perform well on multicore machines. To support our argument, we first present the design, implementation, and evaluation of a barrier on the Intel HARP, a prototype that integrates an x64 processor and FPGA in the same package. This effort gives insight into the potential speed and compactness of hardware barriers, and suggests useful improvements to the HARP platform. Next, we turn to the processor itself and describe an x64 ISA extension for barriers, and how it could be implemented in the microarchitecture with minimal collateral changes. This design allows for barriers to be securely managed jointly between the OS and the application. Finally, we speculate on how barrier synchronization might be implemented on future photonics-based hardware.

The two-dimensional distributions of particles, primary damage, and electronic and nuclear energy loss were calculated for implantation of a line source into silicon targets by using TRIM Monte Carlo code. In addition, the Kinchin-Pease equation was used to calculate approximate two-dimensional distributions of the Frenkel pairs (vacancy-interstitial) created by the primary displacement damage of the target atoms. These distributions allowed for the calculation of the one-dimensional distributions of these quantities for implantation into unmasked targets. The two-dimensional particle and approximate Frenkel pairs distributions for implantation past a mask edge were constructed by means of superposition. The results are important for understanding the mass, energy, and dose dependence of implantation and the associated displacement damage.