标签：it
2015羊年春节到了，总结下2014年分析的哪些IT领域著名定律(Law)
一、规划阶段的指导定律
1. Bell‘s law of computer classes
Definition: Roughly every decade a new, lower priced computer class forms based on a new programming platform,
network, and interface resulting in new usage and the establishment of a new industry.
定义：每10年，新的编程平台、网络、接口会重建产业
http://en.wikipedia.org/wiki/Bell‘s_law_of_computer_classes
2. Moore‘s law
Definition: Integrated circuit density-doubling would occur every 24 months,
integrated circuits would double in performance every 18 months.
定义：集成电路每24个月密度提升1倍，每18个月性能提升1倍。
http://en.wikipedia.org/wiki/Moore%27s_law
3. Kryder‘s law
Definition: Inside of a decade and a half, hard disks had increased their capacity 1,000-fold,
a rate that Intel founder Gordon Moore himself has called "flabbergasting"
定义：HDD每15年容量翻1000倍(比Moore‘s law定义的CPU更快)
http://en.wikipedia.org/wiki/Mark_Kryder
4. Koomey‘s law
Definition: At a fixed computing load, the amount of battery you need will fall by a factor of two every year and a half.
定义：负载相同时，每1.5年能耗下降1/2
http://en.wikipedia.org/wiki/Koomey‘s_law
5. Grosch‘s law
Definition: Computer performance increases as the square of the cost.
If computer A costs twice as much as computer B, you should expect computer A to be four times as fast as computer B.
定义：计算机价格翻倍后，其性能将提升4倍
http://en.wikipedia.org/wiki/Grosch%27s_law
6. Metcalfe‘s law
Definition: The value of a telecommunications network is proportional to the square of the number of connected users of the system (n2).
定义：网络的价值和节点数目n成平方关系
http://en.wikipedia.org/wiki/Metcalfe%27s_law
7. Wirth‘s law
Definition: The speed of software halves every 18 months
定义：软件每18个月处理下降1/2
http://en.wikipedia.org/wiki/Wirth‘s_law
8. Rock‘s law/ Moore‘s 2nd law
Definition: The cost of a semiconductor chip fabrication plant doubles every four years
定义：芯片厂投入成本每4年翻倍
http://en.wikipedia.org/wiki/Rock‘s_law
二、设计实现的指导定律
1. Amdahl law
Definition: The speedup of a program using multiple processors in parallel computing is limited
by the time needed for the sequential fraction of the program
S(n) = 1 / (B + 1/n * (1-B))
定义：并行处理的加速比受程序的串行部分影响
http://en.wikipedia.org/wiki/Amdahl‘s_law
2. Gustafson law
Definition: S(P) = P - x * (P-1)
where P is the number of processors, S is the speedup, and x the non-parallelizable fraction of any parallel process.
定义：并行处理根据核数增加的加速比
http://en.wikipedia.org/wiki/Gustafson‘s_law
3. Little law
Defintion: The long-term average number of customers in a stable system L is equal to the long-term average effective arrival rate,
λ, multiplied by the (Palm?)average time a customer spends in the system, W;
or expressed algebraically:
L = λW.
定义："平均响应时间=并发请求数据量/吞吐率" 或 "响应时间=队列深度*服务时间"
http://en.wikipedia.org/wiki/Little‘s_law
4. 5 miniute rule
Defintion: cache randomly accessed disk pages that are re-used every 5 minutes or less.
定义：保留在内存中的缓存，如果5分钟没有访问，则写入磁盘
http://en.wikipedia.org/wiki/Five-minute_rule
wiki真心不错，未来要把这些定律应用到IT系统的规划、设计、实现中，:)
标签：it
原文地址：http://luoqingchao.blog.51cto.com/688895/1614795
