Multithreading and Multiprocessor Issues

At the moment, the table functions are not thread-safe in a multithreaded environment.

Note that tables and iterators are process-wide, i.e. all threads see the same tables and iterators (think of them as like the Unix current working directory, with the various routines which modify the table or change iterators acting like a Unix chdir() system call).

In a multiprocessor environment, tables are always processor-local.