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

diff --git a/src/misc.erl b/src/misc.erl
index 3aacd3a6cddaa1511cd9e077aa5b107fbad2bd8b..158c11455962cdb91a358cfa226800bae01cf170 100644 (file)
--- a/src/misc.erl
+++ b/src/misc.erl
@@ -446,41 +446,49 @@ best_match(Pattern, Opts) ->
 
 -spec pmap(fun((T1) -> T2), [T1]) -> [T2].
 pmap(Fun, [_,_|_] = List) ->
-    Self = self(),
-    lists:map(
-      fun({Pid, Ref}) ->
-             receive
-                 {Pid, Ret} ->
+    case erlang:system_info(logical_processors) of
+       1 -> lists:map(Fun, List);
+       _ ->
+           Self = self(),
+           lists:map(
+             fun({Pid, Ref}) ->
                      receive
-                         {'DOWN', Ref, _, _, _} ->
-                             Ret
-                     end;
-                 {'DOWN', Ref, _, _, Reason} ->
-                     exit(Reason)
-             end
-      end, [spawn_monitor(
-             fun() -> Self ! {self(), Fun(X)} end)
-           || X <- List]);
+                         {Pid, Ret} ->
+                             receive
+                                 {'DOWN', Ref, _, _, _} ->
+                                     Ret
+                             end;
+                         {'DOWN', Ref, _, _, Reason} ->
+                             exit(Reason)
+                     end
+             end, [spawn_monitor(
+                     fun() -> Self ! {self(), Fun(X)} end)
+                   || X <- List])
+    end;
 pmap(Fun, List) ->
     lists:map(Fun, List).
 
 -spec peach(fun((T) -> any()), [T]) -> ok.
 peach(Fun, [_,_|_] = List) ->
-    Self = self(),
-    lists:foreach(
-      fun({Pid, Ref}) ->
-             receive
-                 Pid ->
+    case erlang:system_info(logical_processors) of
+       1 -> lists:foreach(Fun, List);
+       _ ->
+           Self = self(),
+           lists:foreach(
+             fun({Pid, Ref}) ->
                      receive
-                         {'DOWN', Ref, _, _, _} ->
-                             ok
-                     end;
-                 {'DOWN', Ref, _, _, Reason} ->
-                     exit(Reason)
-             end
-      end, [spawn_monitor(
-             fun() -> Fun(X), Self ! self() end)
-           || X <- List]);
+                         Pid ->
+                             receive
+                                 {'DOWN', Ref, _, _, _} ->
+                                     ok
+                             end;
+                         {'DOWN', Ref, _, _, Reason} ->
+                             exit(Reason)
+                     end
+             end, [spawn_monitor(
+                     fun() -> Fun(X), Self ! self() end)
+                   || X <- List])
+    end;
 peach(Fun, List) ->
     lists:foreach(Fun, List).