Fall back to map/2 and foreach/2 on single-core machines

src/misc.erl

@@ -446,6 +446,9 @@ best_match(Pattern, Opts) ->
 
 -spec pmap(fun((T1) -> T2), [T1]) -> [T2].
 pmap(Fun, [_,_|_] = List) ->
+    case erlang:system_info(logical_processors) of
+	1 -> lists:map(Fun, List);
+	_ ->
 	    Self = self(),
 	    lists:map(
 	      fun({Pid, Ref}) ->
@@ -460,12 +463,16 @@ pmap(Fun, [_,_|_] = List) ->
 		      end
 	      end, [spawn_monitor(
 		      fun() -> Self ! {self(), Fun(X)} end)
-	    || X <- List]);
+		    || X <- List])
+    end;
 pmap(Fun, List) ->
     lists:map(Fun, List).
 
 -spec peach(fun((T) -> any()), [T]) -> ok.
 peach(Fun, [_,_|_] = List) ->
+    case erlang:system_info(logical_processors) of
+	1 -> lists:foreach(Fun, List);
+	_ ->
 	    Self = self(),
 	    lists:foreach(
 	      fun({Pid, Ref}) ->
@@ -480,7 +487,8 @@ peach(Fun, [_,_|_] = List) ->
 		      end
 	      end, [spawn_monitor(
 		      fun() -> Fun(X), Self ! self() end)
-	    || X <- List]);
+		    || X <- List])
+    end;
 peach(Fun, List) ->
     lists:foreach(Fun, List).