Memory Reordering/memory model and its impact on. Net

As for the memory model, this is a really bad topic to talk about. Just came in contact five or six years ago. NET, all the way Daniel began to discuss. I remember the time when I read those words and thoughts with a very respectful heart. After that, often back to reread those words, more feel a lot of harvest. But Daniel often speaks quite simply, so despite the number of reads, most of them become the victims of time and bad memory forgotten. So recently determined to write such a blog, summed up the ideas of heroes, gathered in recent years of the conclusion, plus the author a little insignificant harvest, to ensure accurate and informative, Hope illustrated. Programmers help programmers and everyone else. is for the preface.

Do not know as a programmer you have not thought, if the CPU is not in accordance with your program to write the order (programming orders) to execute, the result will be what? If you have not been aware of this before, you may be more shocked. But after entering the multi-core multiprocessor era, this is the fact that the CPU adjusts the order in which the instructions are executed and executes the instructions in the order of Processer. This is an important measure to improve the efficiency of CPU execution.

Except for a handful of people like. NET Framework designers have encountered this problem very early on, leaving aside the C++/java programmers don't talk, I guess a lot. NET programmer first realized this problem, should be when double-check encountered the implementation of a single example model:

Imperfect Singleton Implement

1.　　public　class　Singleton
2.　{
3.　　　　　　 private　static　object　syncRoot　=　new　object();
4.　　　　　　 private　Singleton　instance;
5.
6.　　　　　　private　 Singleton()　{　}
7.
8.　　　　　　public　Singleton　 Instance
9.　　　　　{
10.　　　　　　　　　　get
11.　　　　 　　　　　{
12.　　　　　　　　　　　　　　if　(instance　==　null)
13.　　　　　　　　　　　　　{
14.　　　　　　　　　　　　　　　 　　　lock　(syncRoot)
15.　　　　　　　　　　　　　　　　　{
16. 　　　　　　　　　　　　　　　　　　　　　　if　(instance　==　null)
17.　　　　　　　　　　　　　　　　　　　　　{
18.　　　　　　　 　　　　　　　　　　　　　　　　　　　instance　=　new　Singleton ();
19.　　　　　　　　　　　　　　　　　　　　　}
20.　　　　　 　　　　　　　　　　　　}
21.　　　　　　　　　　　　　}
22.
23.　　　　　　　　　　　　　　return　instance;
24.　　 　　　　　　　}
25.　　　　　}
26.　}