Amdahl's Law

How do you find a balance between parallelizing a sequential program (by increasing the number of processors) and optimizing the execution speed of the sequential program itself? For example, which is the better option: Having four processors running a given program for 40% of its execution, or using only two processors executing the same program, but for twice as long? This type of trade-off, which is commonly found in concurrent programming, can be strategically analyzed and answered by applying Amdahl's Law.

Additionally, while concurrency and parallelism can be a powerful tool that provides significant improvements in program execution time, they are not a silver bullet that can speed up any non-sequential architecture infinitely and unconditionally. It is therefore important for developers and programmers to know and understand the limits of the speed improvements that concurrency and parallelism offer to their programs, and Amdahl's Law addresses those concerns.