With the traditional lock based (pessimistic) approach, writing reliable and efficient multithreaded programs is impossible given a number "n" of threads. This

With the traditional lock based (pessimistic) approach, writing reliable and efficient multithreaded programs is impossible given a number "n" of threads. This number "n" varies with the talent and experience of the programmer as well, with a less significant factor, with the language used. That's why people are working on transactional memory. When our customers will have 100 cores in their machines, it's not realistic to hope to achieve anything with locks.