Data parallel compilers have long aimed to equal the performance of carefully and-optimized parallel codes. For tightly-coupled applications based on line sweeps, this goal has been particularly elusive. In the Rice dHPF compiler, we have developed a wide spectrum of optimizations that enable us to closely approach hand-coded performance for tightly-coupled line sweep applications including the NAS SP and BT benchmark codes. From lightly-modified copies of standard serial versions of these benchmarks, dHPF generates MPI-based parallel code that is within 4\\% of the performance of the hand-crafted MPI implementations of these codes for a 1023 problem size (Class B) on 64 processors.We describe and quantitatively evaluate the impact of partitioning, communication and memory hierarchy optimizations implemented by dHPF that enable us to approach hand-coded performance with compiler-generated parallel code.