On 08/03/10 15:33, Evan Laforge wrote: >>> Just think of "unsafe" in relation to "unsafeIndex" or something. >>> It's faster, but you have to be sure the index is in bounds. >> Yes, but the whole reason to use "unsafe" is to get higher performance >> at the cost of safety. If the result of calling an "unsafe" foreign >> function is that you *lose* performance because the other threads have >> to be halted first, then this seems to defeat the whole point of marking >> a call as "unsafe" in the first place. > That's why the function has to return soon and shouldn't do a lot of work. But again, then what is the point of marking it "unsafe" if it means that you have to pay a hefty cost of waiting for all the other threads to halt? Is the cost of halting all of the other threads really less than the cost of setting up for a "safe" call? Maybe it is, and that is what I am missing here. If it is not, though, then it seems to me that marking a call as "unsafe" will *never* gain you performance in a multi-threaded environment, so that there is never any point in using it in such an environment. (Though, of course, it could gain you performance in a single-threaded environment.)
Cheers, Greg _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
