How to write a Hello World program for multi-billion users
1 - Some current news, some inspirationshttp://www.forbes.com/2010/04/29/moores-law-computing-processing-opinions-contributors-bill-dally.html
2 - Some technical viewpoints
" Functional programming - treats computation as the evaluation of mathematical functions and avoids state and mutable data. "
So what am I thinking? The mutable data means, you have to or "must" control which function takes this data first if there are some functions concurrently refer to it.
Concurrent case:Integer n = 1;n = n + 1;System.out.print(n);You get 2
Integer n = 1;A thread do n = n + 1;
A another thread do n = n - 1;2 threads use the shared object "Integer n".
2.1 - The waiting for your dinner
- What happens when you share a fork with your friend. You have to wait him.
- Yes, you must use a lot techniques to solve some classic multi-process synchronization problems.
- One of them is the dining philosophers problem(http://en.wikipedia.org/wiki/Dining_philosophers_problem)
- I notice the deadlock happens as it describes "The philosophers never speak to each other, which creates a dangerous possibility of deadlock when every philosopher holds a left fork and waits perpetually for a right fork (or vice versa).
- The cause of this problem is "the shared resources" , here is the fork. We have 5 philosophers , and just 5 forks for them.
- If each philosopher has 2 forks, so nothing to share, and everyone can take his dinner independently.
2.2 - How to write a Hello World program for multi-billion users
In practice, what happens when you develop a system for multi-billion users. If you use the Google, you will understand what I mean.
Check this http://www.slideshare.net/xlight/google-designs-lessons-and-advice-from-building-large-distributed-systems