Sharing ...
•There
are two aspects to sharing memory
–(True)
shared memory means every processor can reference
every memory location of a “single coherent memory,” i.e every processor sees
the same
values
–Shared
address space means every processor can reference every memory location in
the machine
but the memory is not kept coherent
The
problem: Suppose in time sequence
Processor
A reads location 1000
Processor
B writes location 1000
Processors
A and C use 1000 in later computation
When
A, C use values are they the same or different?