Other Mappings

Variations of mapping directives can also be used:

!HPF$ DISTRIBUTE ONTO P        :: A
!HPF$ DISTRIBUTE (BLOCK,BLOCK) :: B

• distribution method missing -- compiler dependent distribution, usually BLOCK,
• processor array missing - compiler dependent grid (determined at runtime),

  This style of distribution is useful during development work when the number of processors may differ between runs.

• all directives missing -- compiler dependent mapping, could be replicated.

  Care must be taken here. Many compilers assume that if an array is not mentioned in any distribution directive then it should be replicated, a copy of the whole array is given to each processor. If this is not what is required then performance will suffer greatly.