-- This is a generic graph coloring library, abstracted over the type of
-- the node keys, nodes and colors.
--
-
-{-# OPTIONS_GHC -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
--- for details
+{-# OPTIONS -fno-warn-missing-signatures #-}
module GraphColor (
module GraphBase,
-- the stack (ie in reverse order) and assigning them colors different to their neighbors.
--
colorGraph
- :: ( Uniquable k, Uniquable cls, Uniquable color, Eq color
+ :: ( Uniquable k, Uniquable cls, Uniquable color
+ , Eq color, Eq cls, Ord k
, Outputable k, Outputable cls, Outputable color)
=> UniqFM (UniqSet color) -- ^ map of (node class -> set of colors available for this class).
-> Triv k cls color -- ^ fn to decide whether a node is trivially colorable.
-> (Graph k cls color -> k) -- ^ fn to choose a node to potentially leave uncolored if nothing is trivially colorable.
-> Graph k cls color -- ^ the graph to color.
- -> ( Graph k cls color -- ^ the colored graph.
- , UniqSet k ) -- ^ the set of nodes that we couldn't find a color for.
+
+ -> ( Graph k cls color -- the colored graph.
+ , UniqSet k -- the set of nodes that we couldn't find a color for.
+ , UniqFM k ) -- map of regs (r1 -> r2) that were coaleced
+ -- r1 should be replaced by r2 in the source
colorGraph colors triv spill graph0
- = let -- run the scanner to slurp out all the trivially colorable nodes
- (ksTriv, ksProblems) = colorScan colors triv spill [] emptyUniqSet graph0
+ = let
+ -- do aggressive coalesing on the graph
+ (graph_coalesced, rsCoalesce)
+ = coalesceGraph triv graph0
+
+ -- run the scanner to slurp out all the trivially colorable nodes
+ (ksTriv, ksProblems)
+ = colorScan triv spill graph_coalesced
-- color the trivially colorable nodes
- (graph1, ksNoTriv) = assignColors colors graph0 ksTriv
+ -- as the keys were added to the front of the list while they were scanned,
+ -- this colors them in the reverse order they were found, as required by the algorithm.
+ (graph_triv, ksNoTriv)
+ = assignColors colors graph_coalesced ksTriv
-- try and color the problem nodes
- (graph2, ksNoColor) = assignColors colors graph1 (uniqSetToList ksProblems)
-
+ (graph_prob, ksNoColor) = assignColors colors graph_triv ksProblems
+
-- if the trivially colorable nodes didn't color then something is wrong
-- with the provided triv function.
in if not $ null ksNoTriv
$$ text "ksNoTriv = " <> ppr ksNoTriv
$$ empty
$$ dotGraph (\x -> text "white") triv graph1) -}
- else (graph2, mkUniqSet ksNoColor)
-
+
+ else ( graph_prob
+ , mkUniqSet ksNoColor
+ , listToUFM rsCoalesce)
+
+-- | Scan through the conflict graph separating out trivially colorable and
+-- potentially uncolorable (problem) nodes.
+--
+-- Checking whether a node is trivially colorable or not is a resonably expensive operation,
+-- so after a triv node is found and removed from the graph it's no good to return to the 'start'
+-- of the graph and recheck a bunch of nodes that will probably still be non-trivially colorable.
+--
+-- To ward against this, during each pass through the graph we collect up a list of triv nodes
+-- that were found, and only remove them once we've finished the pass. The more nodes we can delete
+-- at once the more likely it is that nodes we've already checked will become trivially colorable
+-- for the next pass.
+--
+colorScan
+ :: ( Uniquable k, Uniquable cls, Uniquable color)
+ => Triv k cls color -- ^ fn to decide whether a node is trivially colorable
+ -> (Graph k cls color -> k) -- ^ fn to choose a node to potentially leave uncolored if nothing is trivially colorable.
+ -> Graph k cls color -- ^ the graph to scan
+ -> ([k], [k]) -- triv colorable, problem nodes
+
+
+colorScan triv spill graph
+ = colorScan' triv spill graph
+ [] []
+ []
+ (eltsUFM $ graphMap graph)
+
+-- we've reached the end of the candidates list
+colorScan' triv spill graph
+ ksTriv ksTrivFound
+ ksSpill
+ []
+
+ -- if the graph is empty then we're done
+ | isNullUFM $ graphMap graph
+ = (ksTrivFound ++ ksTriv, ksSpill)
+
+ -- if we haven't found a trivially colorable node then we'll have to
+ -- choose a spill candidate and leave it uncolored
+ | [] <- ksTrivFound
+ , kSpill <- spill graph -- choose a spill candiate
+ , graph' <- delNode kSpill graph -- remove it from the graph
+ , nsRest' <- eltsUFM $ graphMap graph' -- graph has changed, so get new node list
+
+ = colorScan' triv spill graph'
+ ksTriv ksTrivFound
+ (kSpill : ksSpill)
+ nsRest'
+
+ -- we're at the end of the candidates list but we've found some triv nodes
+ -- along the way. We can delete them from the graph and go back for more.
+ | graph' <- foldr delNode graph ksTrivFound
+ , nsRest' <- eltsUFM $ graphMap graph'
+
+ = colorScan' triv spill graph'
+ (ksTrivFound ++ ksTriv) []
+ ksSpill
+ nsRest'
+
+-- check if the current node is triv colorable
+colorScan' triv spill graph
+ ksTriv ksTrivFound
+ ksSpill
+ (node : nsRest)
+
+ -- node is trivially colorable
+ -- add it to the found nodes list and carry on.
+ | k <- nodeId node
+ , triv (nodeClass node) (nodeConflicts node) (nodeExclusions node)
+
+ = colorScan' triv spill graph
+ ksTriv (k : ksTrivFound)
+ ksSpill
+ nsRest
+
+ -- node wasn't trivially colorable, skip over it and look in the rest of the list
+ | otherwise
+ = colorScan' triv spill graph
+ ksTriv ksTrivFound
+ ksSpill
+ nsRest
+
+{- -- This is cute and easy to understand, but too slow.. BL 2007/09
+
colorScan colors triv spill safe prob graph
-- empty graphs are easy to color.
| k <- spill graph
= colorScan colors triv spill
safe (addOneToUniqSet prob k) (delNode k graph)
-
+-}
-- | Try to assign a color to all these nodes.
assignColors colors graph ks
= assignColors' colors graph [] ks
- where assignColors' colors graph prob []
+ where assignColors' _ graph prob []
= (graph, prob)
assignColors' colors graph prob (k:ks)
-- we got one of our preferences, score!
| not $ isEmptyUniqSet colors_ok_pref
- , c : rest <- uniqSetToList colors_ok_pref
+ , c : _ <- uniqSetToList colors_ok_pref
= Just c
-- it wasn't a preference, but it was still ok
| not $ isEmptyUniqSet colors_ok
- , c : rest <- uniqSetToList colors_ok
+ , c : _ <- uniqSetToList colors_ok
= Just c
-- leave this node uncolored
projects / ghc-hetmet.git / blobdiff