[windust]

You're assuming that the code is executing in the way you read it, which is false. With the advent of branch prediction and Instruction reordering in CPUS (to gain performance), a CPU have the liberty of reordering operations for efficiency (http://en.wikipedia.org/wiki/Out-of-order_execution) EXCEPT when there are memory barriers (or explicit synchronization instructions). With a multi-core processor things get even more complex, as you have cache locality (a thread reading the point value might be hitting the CPU cache and not main memory). If the thread happens to be executing on a different core than the assigning thread, disaster ensues.