Unified Sequential Optimization Directives in OpenMP.

OpenMP began as a mechanism to support portability of shared-memory, loop-level parallelization via directives. OpenMP has become widely popular due to the high value that users place on portability. Its original motivation has justified additions to its specification to support SIMD parallelism and, as has been adopted for OpenMP 5.1, directives for common loop optimizations such as tiling and unrolling.