Florian Hartwig wrote:
Heinrich Apfelmus wrote:
So while the two are related, CAS is a machine primitive that works for a single operation and on a single word while STM is a software abstraction that isolates sequences of operations on multiple memory locations from each other.
Is it possible to implement every data structure based on CAS in terms of STM? What are the drawbacks? The other way round?
I think so. Atomically reading and writing a single memory location (which CAS does) is just a very simple transaction. But using a CAS instruction should be more efficient, since STM has to maintain a transaction log and commit transactions, which creates some overhead.
Ah, I see. In that case, it may be worthwhile to implement the CAS instruction in terms of STM as well and measure the performance difference this makes for the final data structure. After all, STM is a lot more compositional than CAS, so I'd like to know whether the loss of expressiveness is worth the gain in performance. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com