Law of parallel programming

Question

There is a law of parallel programming but I can't find a link to it. Shortly it tells the following: if 1/3 of time your program is executed sequentially (in one thread), you can increase your application performance only 3 times.

Answer 1

Amdahl's law refers to the old single-core CPUs. You may want to read carefully what happens on current multi-core CPUs. See

Amdahl's Law in the Multicore Era

and the related page where you will find additional resources.

Answer 2

That would be Amdahl's Law.