GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/GF/Devel/Compile/Factorize.hs

@@ -0,0 +1,251 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : OptimizeGF
+-- Maintainer  : AR
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/04/21 16:21:33 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.6 $
+--
+-- Optimizations on GF source code: sharing, parametrization, value sets.
+--
+-- optimization: sharing branches in tables. AR 25\/4\/2003.
+-- following advice of Josef Svenningsson
+-----------------------------------------------------------------------------
+
+module GF.Devel.Compile.Factorize (
+  optModule,
+  unshareModule,
+  unsubexpModule,
+  unoptModule,
+  subexpModule,
+  shareModule
+  ) where 
+
+import GF.Devel.Grammar.Grammar
+import GF.Devel.Grammar.Construct
+import GF.Devel.Grammar.PrGF (prt)
+import qualified GF.Devel.Grammar.Macros as C
+
+import GF.Devel.Grammar.Lookup
+import GF.Infra.Ident
+
+import GF.Data.Operations
+
+import Control.Monad
+import Data.Map (Map)
+import qualified Data.Map as Map
+import Data.List
+
+optModule :: SourceModule -> SourceModule
+optModule = subexpModule . shareModule
+
+shareModule = processModule optim
+
+unoptModule :: GF -> SourceModule -> SourceModule
+unoptModule gr = unshareModule gr . unsubexpModule
+
+unshareModule :: GF -> SourceModule -> SourceModule
+unshareModule gr = processModule (const (unoptim gr))
+
+processModule :: (Ident -> Term -> Term) -> SourceModule -> SourceModule
+processModule opt (i,mo) = 
+  (i, mo {mjments = Map.map (shareInfo (opt i)) (mjments mo)})
+
+shareInfo :: (Term -> Term) -> Judgement -> Judgement
+shareInfo opt ju = ju {jdef = opt (jdef ju)}
+
+-- the function putting together optimizations
+optim :: Ident -> Term -> Term
+optim c = values . factor c 0
+
+-- we need no counter to create new variable names, since variables are 
+-- local to tables ----
+-- factor parametric branches
+
+factor :: Ident -> Int -> Term -> Term
+factor c i t = case t of
+  T _ [_] -> t
+  T _ []  -> t
+  T (TComp ty) cs -> 
+    T (TTyped ty) $ factors i [(p, factor c (i+1) v) | (p, v) <- cs]
+  _ -> C.composSafeOp (factor c i) t
+ where
+
+   factors i psvs =   -- we know psvs has at least 2 elements
+     let p   = qqIdent c i
+         vs' = map (mkFun p) psvs
+     in if   allEqs vs'
+        then mkCase p vs' 
+        else psvs
+
+   mkFun p (patt, val) = replace (C.patt2term patt) (Vr p) val
+
+   allEqs (v:vs) = all (==v) vs
+
+   mkCase p (v:_) = [(PV p, v)]
+
+--- we hope this will be fresh and don't check... 
+
+qqIdent c i = identC ("_q_" ++ prt c ++ "__" ++ show i)
+
+
+--  we need to replace subterms
+
+replace :: Term -> Term -> Term -> Term
+replace old new trm = case trm of
+  
+  -- these are the important cases, since they can correspond to patterns  
+  QC _ _   | trm == old -> new
+  App t ts | trm == old -> new
+  App t ts              -> App (repl t) (repl ts)
+  R _ | isRec && trm == old -> new
+  _ -> C.composSafeOp repl trm
+ where
+   repl = replace old new
+   isRec = case trm of
+     R _ -> True
+     _ -> False
+
+-- It is very important that this is performed only after case
+-- expansion since otherwise the order and number of values can
+-- be incorrect. Guaranteed by the TComp flag.
+
+values :: Term -> Term
+values t = case t of
+  T ty [(ps,t)]    -> T ty [(ps,values t)] -- don't destroy parametrization
+  T (TComp ty)  cs -> V ty [values t | (_, t) <- cs]
+  T (TTyped ty) cs -> V ty [values t | (_, t) <- cs] 
+        ---- why are these left?
+        ---- printing with GrammarToSource does not preserve the distinction
+  _ -> C.composSafeOp values t
+
+
+-- to undo the effect of factorization
+
+unoptim :: GF -> Term -> Term
+unoptim gr = unfactor gr
+
+unfactor :: GF -> Term -> Term
+unfactor gr t = case t of
+  T (TTyped ty) [(PV x,u)] -> V ty [restore x v (unfac u) | v <- vals ty]
+  _ -> C.composSafeOp unfac t
+ where
+   unfac = unfactor gr
+   vals  = err error id . allParamValues gr
+   restore x u t = case t of
+     Vr y | y == x -> u
+     _ -> C.composSafeOp (restore x u) t
+
+
+----------------------------------------------------------------------
+
+{-
+This module implements a simple common subexpression elimination
+ for gfc grammars, to factor out shared subterms in lin rules.
+It works in three phases: 
+
+  (1) collectSubterms collects recursively all subterms of forms table and (P x..y)
+      from lin definitions (experience shows that only these forms
+      tend to get shared) and counts how many times they occur
+  (2) addSubexpConsts takes those subterms t that occur more than once
+      and creates definitions of form "oper A''n = t" where n is a
+      fresh number; notice that we assume no ids of this form are in
+      scope otherwise
+  (3) elimSubtermsMod goes through lins and the created opers by replacing largest
+      possible subterms by the newly created identifiers
+
+The optimization is invoked in gf by the flag i -subs.
+
+If an application does not support GFC opers, the effect of this
+optimization can be undone by the function unSubelimCanon.
+
+The function unSubelimCanon can be used to diagnostisize how much
+cse is possible in the grammar. It is used by the flag pg -printer=subs.
+
+-}
+
+subexpModule :: SourceModule -> SourceModule
+subexpModule (m,mo) = errVal (m,mo) $ case mtype mo of
+  MTAbstract -> return (m,mo)
+  _ -> do
+    let js = listJudgements mo
+    (tree,_) <- appSTM (getSubtermsMod m js) (Map.empty,0)
+    js2 <- addSubexpConsts m tree js
+    return (m, mo{mjments = Map.fromList js2})
+
+unsubexpModule :: SourceModule -> SourceModule
+unsubexpModule (m,mo) = (m, mo{mjments = rebuild (mjments mo)})
+  where
+    unparInfo (c, ju) = case jtype ju of
+      EInt 8 -> [] -- subexp-generated opers
+      _ -> [(c, ju {jdef = unparTerm (jdef ju)})]
+    unparTerm t = case t of
+      Q _ c@(IC ('_':'A':_)) -> --- name convention of subexp opers
+        maybe t (unparTerm . jdef) $ Map.lookup c (mjments mo)
+      _ -> C.composSafeOp unparTerm t
+    rebuild = Map.fromList . concat . map unparInfo . Map.assocs
+
+-- implementation
+
+type TermList = Map Term (Int,Int) -- number of occs, id
+type TermM a = STM (TermList,Int) a
+
+addSubexpConsts :: 
+  Ident -> Map Term (Int,Int) -> [(Ident,Judgement)] -> Err [(Ident,Judgement)]
+addSubexpConsts mo tree lins = do
+  let opers = [oper id trm | (trm,(_,id)) <- list]
+  mapM mkOne $ opers ++ lins
+ where
+
+   mkOne (f, def) = return (f, def {jdef = recomp f (jdef def)})
+   recomp f t = case Map.lookup t tree of
+     Just (_,id) | ident id /= f -> Q mo (ident id)
+     _ -> C.composSafeOp (recomp f) t
+
+   list = Map.toList tree
+
+   oper id trm = (ident id, resOper (EInt 8) trm)
+   --- impossible type encoding generated opers
+
+getSubtermsMod :: Ident -> [(Ident,Judgement)] -> TermM (Map Term (Int,Int))
+getSubtermsMod mo js = do
+  mapM (getInfo (collectSubterms mo)) js
+  (tree0,_) <- readSTM
+  return $ Map.filter (\ (nu,_) -> nu > 1) tree0
+ where
+   getInfo get fi@(_,i) = do
+     get (jdef i)    
+     return $ fi
+
+collectSubterms :: Ident -> Term -> TermM Term
+collectSubterms mo t = case t of
+  App f a -> do
+    collect f
+    collect a
+    add t 
+  T ty cs -> do
+    let (_,ts) = unzip cs
+    mapM collect ts
+    add t
+  V ty ts -> do
+    mapM collect ts
+    add t
+----  K (KP _ _)  -> add t
+  _ -> C.composOp (collectSubterms mo) t
+ where
+   collect = collectSubterms mo
+   add t = do
+     (ts,i) <- readSTM
+     let 
+       ((count,id),next) = case Map.lookup t ts of
+         Just (nu,id) -> ((nu+1,id), i)
+         _ ->            ((1,   i ), i+1)
+     writeSTM (Map.insert t (count,id) ts, next)
+     return t --- only because of composOp
+
+ident :: Int -> Ident
+ident i = identC ("_A" ++ show i) ---
+