4 ms·
The article severely misrepresents Amdahl's law, in particular in the sentence: > Though you took half of your entire program, and optimized it to be four time
by rav 9y ago
The article severely misrepresents Amdahl's law, in particular in the sentence:
> Though you took half of your entire program, and optimized it to be four times faster, the overall system is only 1.6x faster.
This application of Amdahl's law doesn't tell you anything about what happens when you take half of the program; it tells you what happens when you take half of the execution time. If you only get a 1.6x speedup, it means you optimized the wrong part of the program!
Suppose 20% of the program is responsible for 80% of the execution time. If you speed up this bit four times, you end up with a 2.5x speedup (and not a 1.18x speedup as the article tries to imply).
- taneq 9y agoBasically this. The article makes it sound like "optimizing half the program" means "optimizing half of the codebase", not "optimizing a part of the codebase that consumes 50% of the execution time." This quote is especially misleading: > Amdahl’s Law is telling us that to significantly improve the speed of a system, we’ll have to improve a very large fraction of it. No, it's telling us we'll have to improve the part of it which is responsible for a very large fraction of the execution time. Often this is only a tiny amount of the overall codebase.