Experimental: parallel batch compilation of grammars

On my laptop these changes speed up the full build of the RGL and example
grammars with 'cabal build' from ~95s to ~43s and the zero build from ~18s
to ~5s.

The main change is the introduction of the module GF.CompileInParallel that
replaces GF.Compile and the function GF.Compile.ReadFiles.getAllFiles. At
present, it is activated with the new -j flag, and it is only used when
combined with --make or --batch. In addition, to get parallel computations,
you need to add GHC run-time flags, e.g., +RTS -N -A20M -RTS, to the command
line.

The Setup.hs script has been modified to pass the appropriate flags to GF
for parallel compilation when compiling the RGL and example grammars, but you
need a recent version of Cabal for this to work (probably >=1.20).

Some additonal refactoring were made during this work. A new monad is used to
avoid warnings/error messages from different modules to be intertwined when
compiling in parallel, so some functios that were hardiwred to the IO or IOE
monads have been lifted to work in arbitrary monads that are instances in
the appropriate classes.

src/compiler/GF/Compile/GetGrammar.hs

@@ -25,29 +25,29 @@ import GF.Grammar.Parser
 import GF.Grammar.Grammar
 import GF.Grammar.CFG
 import GF.Grammar.EBNF
-import GF.Compile.ReadFiles(parseSource,lift)
+import GF.Compile.ReadFiles(parseSource)
 
 import qualified Data.ByteString.Char8 as BS
 import Data.Char(isAscii)
 import Control.Monad (foldM,when,unless)
 import System.Process (system)
-import System.Directory(removeFile,getCurrentDirectory)
+import GF.System.Directory(removeFile,getCurrentDirectory)
 import System.FilePath(makeRelative)
 
-getSourceModule :: Options -> FilePath -> IOE SourceModule
+--getSourceModule :: Options -> FilePath -> IOE SourceModule
 getSourceModule opts file0 = 
 --errIn file0 $
-  do tmp <- lift $ foldM runPreprocessor (Source file0) (flag optPreprocessors opts)
-     raw <- lift $ keepTemp tmp
+  do tmp <- liftIO $ foldM runPreprocessor (Source file0) (flag optPreprocessors opts)
+     raw <- liftIO $ keepTemp tmp
    --ePutStrLn $ "1 "++file0
      (optCoding,parsed) <- parseSource opts pModDef raw
      case parsed of
-       Left (Pn l c,msg) -> do file <- lift $ writeTemp tmp
-                               cwd <- lift $ getCurrentDirectory
+       Left (Pn l c,msg) -> do file <- liftIO $ writeTemp tmp
+                               cwd <- getCurrentDirectory
                                let location = makeRelative cwd file++":"++show l++":"++show c
                                raise (location++":\n   "++msg)
        Right (i,mi0) ->
-         do lift $ removeTemp tmp
+         do liftIO $ removeTemp tmp
             let mi =mi0 {mflags=mflags mi0 `addOptions` opts, msrc=file0}
                 optCoding' = renameEncoding `fmap` flag optEncoding (mflags mi0)
             case (optCoding,optCoding') of
@@ -59,7 +59,7 @@ getSourceModule opts file0 =
                   raise $ "Encoding mismatch: "++coding++" /= "++coding'
                 where coding = maybe defaultEncoding renameEncoding optCoding
               _ -> return ()
-          --lift $ transcodeModule' (i,mi) -- old lexer
+          --liftIO $ transcodeModule' (i,mi) -- old lexer
             return (i,mi) -- new lexer
 
 getCFRules :: Options -> FilePath -> IOE [CFRule]
@@ -67,7 +67,7 @@ getCFRules opts fpath = do
   raw <- liftIO (BS.readFile fpath)
   (optCoding,parsed) <- parseSource opts pCFRules raw
   case parsed of
-    Left (Pn l c,msg) -> do cwd <- lift $ getCurrentDirectory
+    Left (Pn l c,msg) -> do cwd <- getCurrentDirectory
                             let location = makeRelative cwd fpath++":"++show l++":"++show c
                             raise (location++":\n   "++msg)
     Right rules       -> return rules
@@ -77,7 +77,7 @@ getEBNFRules opts fpath = do
   raw <- liftIO (BS.readFile fpath)
   (optCoding,parsed) <- parseSource opts pEBNFRules raw
   case parsed of
-    Left (Pn l c,msg) -> do cwd <- lift $ getCurrentDirectory
+    Left (Pn l c,msg) -> do cwd <- getCurrentDirectory
                             let location = makeRelative cwd fpath++":"++show l++":"++show c
                             raise (location++":\n   "++msg)
     Right rules       -> return rules