In an ideal world, concurrency need not be a problem. After all, we can say that it is simply a matter of checking the safety of every read/write against every

In an ideal world, concurrency need not be a problem. After all, we can say that it is simply a matter of checking the safety of every read/write against every possible state of every thread that may be running concurrently. However, the reality is that developers can not do this checking with complete accuracy. The simplistic reason is that the complexity of concurrent programs is exponentially greater than that of non-concurrent programs. In a concurrent model if I have m threads of execution and n read/writes per thread I need to verify n^m states in my code. Such a blowup in state makes any reasonable person look for generalizations and optimizations, but those then lead incorrect assumptions and ultimately defects. Outside of this simplistic reasoning lie other problems which serve to exacerbate code verification during design and construction; realities of deadlines, access to source or documentation of components, the learning curve of technologies used as black boxes.