Amdahl's Law
Example:
Suppose a program runs in 100 seconds on a machine, with multiply responsible for 80 seconds of this time. How much do we have to improve the speed of multiplication if we want the program to run 5 times faster?"
Ans:
Execution time affected by improvement (T affected) = 80s
Execution time unaffected (T unaffected) = 20s
5 times:
20 = 80/n + 20 --> n = 0 So, 不可能 5 times
