Primitive Operations

The Eden implementation exposes coordination control and communication to Haskell level, and uses the defined primitives in the internals of a module Eden.hs (this part is not relevant for the GpH variant, but might be interesting even though).

• runtime information primitives: noPe#, selfPe#
• placeholder creation and registration: expectData#
• connecting a thread to a registered inport: connectInport#
• sending graph structures: sendData# (also implementing remote process creation by a special send mode)

These primitives (see rts/PrimOps.c) use the RTS functionality we have put in place earlier.

NB: if at all possible, we should make sure all primitives do something expectable and sensible in the non-parallel case. This is not true for expectData#

Simple operations like selfPe / noPe only read variables inside the runtime system. They can be (and were) implemented as primitive operations, but the best way is to implement them in Haskell by simply reading a (foreign-import'ed) C Int (as done for Concurrent Haskell's numCapabilities as well):

foreign import ccall "&nPEs" nPEs :: Ptr CInt
foreign import ccall "&thisPE" thisPE :: Ptr CInt
noPe,selfPe :: Int
noPe = unsafePerformIO $  do
              n <- peek nPEs
              return (fromIntegral n)
selfPe = unsafePerformIO $  do
              n <- peek thisPE
              return (fromIntegral n)