Indirection arrays generally require expensive scheduling. By careful programming, one can reduce the number of schedules generated. Another technique that allows the compiler to optimize this type of communication is indirection array alignment. Another optimization that a programmer may use involves generating indirection arrays to reduce the use of expensive scalar communications. If you are comparing an HPF program to check its performance using several different algorithms, there are several relevant parameters to use when measuring performance.
Parallel speedup measures the decrease in program execution time as more processors are added.
If is the time to execute the program with i processors, then perfect speedup occurs when . Another measure of speedup that may be used is the comparison of a program's parallel execution time with the execution time of an optimized sequential version of the program.