parmap.py: no subprocesses when nprocs == 1

parmap.py

@@ -87,6 +87,10 @@ def parmap(f, X, nprocs = None, chunksize = 1, chunks_in_flight = None,
     if nprocs is None:
       nprocs = multiprocessing.cpu_count()
 
+    if nprocs == 1:
+      if multimap: return chain.from_iterable(map(f, X))
+      else: return map(f, X)
+
     if in_order:
       out_chunksize = None