turn off TimerOutputs when using threads

Author: marius311

src/util.jl

@@ -373,11 +373,17 @@ end
 See [`@⌛`](@ref)
 """
 macro show⌛(ex)
-    quote
-        reset_timer!(get_defaulttimer())
-        result = $(esc(ex))
-        show(get_defaulttimer())
-        result
+    if Threads.nthreads()>1
+        # TimerOutputs is not thread-safe
+        # https://github.com/KristofferC/TimerOutputs.jl/issues/72
+        esc(ex)
+    else
+        quote
+            reset_timer!(get_defaulttimer())
+            result = $(esc(ex))
+            show(get_defaulttimer())
+            result
+        end
     end
 end