Re: Parallel --make (GHC build times on newer MacBook Pros?)

On Mon, Aug 29, 2011 at 1:50 PM, Max Bolingbroke wrote:

On 27 August 2011 09:00, Evan Laforge wrote:

...

Right, that's probably the one I mentioned.  And I think he was trying to parallelize ghc internally, so even compiling one file could parallelize.  That would be cool and all, but seems like a lot of work compared to just parallelizing at the file level, as make would do.

It was Thomas Schilling, and he wasn't trying to parallelise the compilation of a single file. He was just trying to make access to the various bits of shared state GHC uses thread safe. This mostly worked but caused an unacceptable performance penalty to single-threaded compilation.

Interesting, maybe I misremembered? Or maybe there was some other guy who was trying to parallelize? Just out of curiosity, what benefit does a thread-safe ghc provide? I know ghc api users have go to some bother to not call re-entrantly... what neat stuff could we do with a re-entrant ghc? Could it eventually lead to an internally parallel ghc or are there deeper reasons it's hard to parallelize compilation? That would be really cool, if possible. In fact, I don't know of any parallel compilers.