Whoops! Didn't know that was necessary - it works now...
Oh, did you also add a>> I tried LIBMESH_BEST_UNORDERED_SET... and I got this:
>>
>> error: std::tr1¹ has not been declared
>>
>> So apparently, that configure test isn't doing the right thing on my Mac. I
>> guess we must not be using this anywhere else in the code...
>
> That's curious - can you send me your config.log directly to avoid the
> attachment filter?
>
> It should be very similar to the BEST_UNORDERED_MAP which we do use...
#include LIBMESH_INCLUDE_UNORDERED_SET
header entry?
-Ben