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.

1 files changed, 10 insertions, 3 deletions

diff --git a/src/compiler/GFC.hs b/src/compiler/GFC.hs
index 4b1034faa..6f909b511 100644
--- a/src/compiler/GFC.hs
+++ b/src/compiler/GFC.hs
@@ -4,7 +4,8 @@ module GFC (mainGFC, writePGF) where
 import PGF
 import PGF.Internal(concretes,optimizePGF,unionPGF)
 import PGF.Internal(putSplitAbs,encodeFile,runPut)
-import GF.Compile
+import GF.Compile as S(batchCompile,link,srcAbsName)
+import qualified GF.CompileInParallel as P(batchCompile)
 import GF.Compile.Export
 import GF.Compile.CFGtoPGF
 import GF.Compile.GetGrammar
@@ -41,7 +42,7 @@ mainGFC opts fs = do
 
 compileSourceFiles :: Options -> [FilePath] -> IOE ()
 compileSourceFiles opts fs = 
-    do cnc_gr@(cnc,t_src,gr) <- batchCompile opts fs
+    do (t_src,~cnc_grs@(~(cnc,gr):_)) <- batchCompile opts fs
        unless (flag optStopAfterPhase opts == Compile) $
               do let abs = showIdent (srcAbsName gr cnc)
                      pgfFile = outputPath opts (grammarName' opts abs<.>"pgf")
@@ -50,9 +51,15 @@ compileSourceFiles opts fs =
                           else return Nothing
                  if t_pgf >= Just t_src
                    then putIfVerb opts $ pgfFile ++ " is up-to-date."
-                   else do pgf <- link opts cnc_gr
+                   else do pgfs <- mapM (link opts)
+                                        [(cnc,t_src,gr)|(cnc,gr)<-cnc_grs]
+                           let pgf = foldl1 unionPGF pgfs
                            writePGF opts pgf
                            writeOutputs opts pgf
+  where
+    batchCompile = maybe batchCompile' P.batchCompile (flag optJobs opts)
+    batchCompile' opts fs = do (cnc,t,gr) <- S.batchCompile opts fs
+                               return (t,[(cnc,gr)])
 
 compileCFFiles :: Options -> [FilePath] -> IOE ()
 compileCFFiles opts fs = do