Language Constructs for Safe Parallel Programming on Multi-Cores

ešects and checking are implemented in the compiler. emore speculative gradual ešect checking remains to be implemented. We have also not yet completely formalized or proven the soundness of the gradual ešect system. 5.5 Unlocking Ešects Using ešects for data race-free parallelism is conceptually very similar to using locks. Annotating a method with an ešect clause ešectively locks the data described by the ešects during the execution of that method, preventing any other conžicting method execution. ere are two major dišerences, however, one favoring ešects and one favoring locks. First, with an ešect clause, all the necessary “locks” can be acquired by a single atomic operation, whereas acquiring several actual locks is done in sequence (non-atomic), which is slower and also may introduce deadlocks. Secondly, ešects are held for an entire computation (a method typically), whereas locks can be released as soon as they are no longer needed; consequently locks may allow for more parallelism. To remedy this shortcomingwe introduce a yield command.A yield can be used inside a method body to inform the scheduler that an ešect reported in the method’s head will not be caused by the remainder of that method. is allows