解决 Branch Hazards 的n种方法

static branch prediction

1. freeze of flush the pipeline (predicted-not-taken)

NP完全性的核心逻辑

NP完全问题是为了反映一个问题有多难，而不是为了反应它有多简单

Types of variables

1. Environment/Global Variables
2. Shell/Local Variables

The difference between these two variables is that environment variables can be interviewed by child processes, i.e. the so-called global variables are only shared within the process hierarchy of the current process（进程链）, existing only between the current process and its child processes. Environment variables of other processes and those of the current process are not shared. But Shell variables can only be interviewed by current process.

variables¹

It should be noted that the usage of site a variable in makefile is different from using it in shell.

Asynchronization (Multithreading)

The first thing we need to do is understanding the correlations between multithreading and parallel computing.

Data Model

The following pseudo code can explain the git data model clearly.