Parallelization as program transformation

• Parallelization process:
  • A transformation of the original program into a parallelized (``annotated'') program in a concurrent/parallel language.
  • Prolog/CLP &-Prolog / Ciao-Prolog

• &-Prolog / Ciao-Prolog in brief:
  • Prolog/CLP (with if-then-else)
  • Parallel conjunction ``&/2'' (correct forwards and backwards semantics)
  • Primitives to detect parallelism conditions at run-time, when static analysis is not enough
  • (Synchronization primitives, concurrency &/1, ...)
  • (Tracing and control primitives)

Example:

qs([X|L],R) :- part(L,X,L1,L2), qs(L2,R2), qs(L1,R1), 
               app(R1,[X|R2],R).

qs([X|L],R) :- 
         part(L,X,L1,L2), 
         (  ground(L1), ground(L2) 
         -> 
            qs(L2,R2) & qs(L1,R1)
         ;  
            qs(L2,R2), qs(L1,R1) ), 
         app(R1,[X|R2],R).