Re: RFC: Implicit Parallelization Pragma

[Jenda]

The pragma is supposed to be lexical? What would

@foo = map {use threadsafe; $_ = foo($_)} @bar;

mean then? Is the foo() to be treated as threadsafe or not? And can the block be paralelized?

Let's assume first that the {use threadsafe; ...} means that the contents of this block may be parallelized. No matter what subs do you call within. The programmer would have to be very very carefull then and it would take him ages to validate each and every subroutine that might get called. And the bigger the task (and thus the better candidate for parallel execution) the harder would it be to validate it. So I doubt people would use this often, if at all.

What about if the use threadsafe; mean just that the code in the block is threadsafe, but would not say anything about the subroutines. And the interpreter would be alowed to parallelize the execution only if also all subroutines used in the block are marked threadsafe. The problem then is ... who's going to mark them? And if I mark a subroutine threadsafe, does it mean I've just said even the subroutines called from within are threadsafe? What if the implementation of a subroutine I use from a module changes and it no longer is? Or does it mean that the compiler should check the threadsafety of the subroutines used within the one it just compiles and either die or warn and ignore the mark if it uses a subroutine that's not threadsafe? The second is of course much safer, but requires changes in other people's modules!