== 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)
}}}


[wiki:GpHEden --> back to GpHEden]