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-- Copyright (c) 2009-2011, ERICSSON AB
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--

module Feldspar.Par
  ( P
  , IVar
  , runPar
  , new
  , get
  , put
  , fork
  , yield
  , spawn
  , pval
  , parMap
  , parMapM
  )
where

import Language.Syntactic

import Feldspar.Core.Constructs (Syntax(..))
import Feldspar.Core.Constructs.Par
import Feldspar.Core.Frontend.Par

runPar :: Syntax a => P a -> a
runPar = sugarSym ParRun

new :: Syntax a => P (IVar a)
new = sugarSym ParNew

get :: Syntax a => IVar a -> P a
get = sugarSym ParGet

put :: Syntax a => IVar a -> a -> P ()
put = sugarSym ParPut

fork :: P () -> P ()
fork = sugarSym ParFork

yield :: P ()
yield = sugarSym ParYield

spawn :: Syntax a => P a -> P (IVar a)
spawn p = do
    r <- new
    fork (p >>= put r)
    return r

pval a = spawn (return a)

parMap f xs = mapM (pval . f) xs >>= mapM get

parMapM f xs = mapM (spawn . f) xs >>= mapM get

{-
divConq :: (prob -> Bool)   -- indivisible?
        -> (prob -> [prob]) -- split into subproblems
        -> ([sol] -> [sol]) -- join solutions
        -> (prob -> sol)    -- solve a (sub)problem
        -> (prob -> sol)
-}
divConq indiv split join f prob = go prob
  where
    go prob | indiv prob = return (f prob)
            | otherwise  = do
                sols <- parMapM go (split prob)
                return (join sols)