Lecture 24: Critical Thinking. Code Optimization Aspects.

Lecture Summary

• Last time

  • Parallel computing, multi-core: how caches come into play

  • Critical thinking, and similar tricks for speeding up your code

• Today

  • Critical thinking, and other similar tricks for speeding up your code

Know your hardware

Know your bandwidth/latency

Choose the right algorithm

• When working on a problem, there's more to performance than asymptotic complexity

  • Because asymptotic complexity is most often defined by the number of operations

  • Memory transactions are rarely considered: they are specific to the hardware

• Assess the arithmetic intensity associated with your problem

• Simple optimization: Fusing transformations and do not bring data into the cache twice

Compiler

• Aggressive optimizations done by the compiler might change the behavior of your code

• To help the compiler:

  • Allow it to see as much code as possible

  • Provide flags to convey information (e.g., the target architecture)

• There are a lot of amazing things covered in this lecture. The takeaways are:

  • Compilers are fantastic

  • Know them better to use them wisely

• A quick example is down below. Refer to the slides for a lot more fun facts