Merge pull request #3449 from amitmurthy/amitm/fetchfrom

Implemented @fetch and @fetchfrom, the fetch versions of @Spawn and @spa...

base/exports.jl

@@ -1227,6 +1227,8 @@ export
     @spawn,
     @spawnlocal,  # deprecated
     @spawnat,
+    @fetch,
+    @fetchfrom,
     @everywhere,
     @parallel,
     @gensym,

base/multi.jl

@@ -1072,8 +1072,6 @@ function sync_add(r)
     r
 end
 
-spawnat(p, thunk) = sync_add(remotecall(p, thunk))
-
 let nextidx = 1
     global chooseproc
     function chooseproc(thunk::Function)
@@ -1102,13 +1100,34 @@ let nextidx = 1
     end
 end
 
+spawnat(p, thunk) = sync_add(remotecall(p, thunk))
+
 spawn_somewhere(thunk) = spawnat(chooseproc(thunk),thunk)
 
 macro spawn(expr)
     expr = localize_vars(:(()->($expr)), false)
     :(spawn_somewhere($(esc(expr))))
 end
 
+macro spawnat(p, expr)
+    expr = localize_vars(:(()->($expr)), false)
+    :(spawnat($(esc(p)), $(esc(expr))))
+end
+
+macro fetch(expr)
+    expr = localize_vars(:(()->($expr)), false)
+    quote
+        thunk = $(esc(expr))
+        remotecall_fetch(chooseproc(thunk), thunk)
+    end
+end
+
+macro fetchfrom(p, expr)
+    expr = localize_vars(:(()->($expr)), false)
+    :(remotecall_fetch($(esc(p)), $(esc(expr))))
+end
+
+
 function spawnlocal(thunk)
     rr = RemoteRef(myid())
     sync_add(rr)
@@ -1132,11 +1151,6 @@ macro spawnlocal(expr)
     :(@async $(esc(expr)))
 end
 
-macro spawnat(p, expr)
-    expr = localize_vars(:(()->($expr)), false)
-    :(spawnat($(esc(p)), $(esc(expr))))
-end
-
 function at_each(f, args...)
     for w in PGRP.workers
         sync_add(remotecall(w.id, f, args...))

test/parallel.jl

@@ -6,6 +6,8 @@ id_me = myid()
 id_other = filter(x -> x != id_me, procs())[rand(1:(nprocs()-1))]
 
 @test fetch(@spawnat id_other myid()) == id_other
+@test @fetchfrom id_other begin myid() end == id_other
+@fetch begin myid() end
 
 d = drand((200,200), [id_me, id_other])
 s = convert(Array, d[1:150, 1:150])