Re: DiffArray Performance

The problem was whether DiffArrays should be thread-safe in the Concurrent Haskell sense, which means protecting access to the DiffArray with an MVar.

Can you give some estimate of the cost of using an MVar in this way? Could some cheaper mechanism be provided for the special case of a mutex? e.g., the moral equivalent of disabling interrupts might be cheaper (though I'd want to look at the diffarray code again before deciding if that style of solution were appropriate). -- Alastair