Book Image

The Art of Writing Efficient Programs

By : Fedor G. Pikus
3 (2)
Book Image

The Art of Writing Efficient Programs

3 (2)
By: Fedor G. Pikus

Overview of this book

The great free lunch of "performance taking care of itself" is over. Until recently, programs got faster by themselves as CPUs were upgraded, but that doesn't happen anymore. The clock frequency of new processors has almost peaked, and while new architectures provide small improvements to existing programs, this only helps slightly. To write efficient software, you now have to know how to program by making good use of the available computing resources, and this book will teach you how to do that. The Art of Efficient Programming covers all the major aspects of writing efficient programs, such as using CPU resources and memory efficiently, avoiding unnecessary computations, measuring performance, and how to put concurrency and multithreading to good use. You'll also learn about compiler optimizations and how to use the programming language (C++) more efficiently. Finally, you'll understand how design decisions impact performance. By the end of this book, you'll not only have enough knowledge of processors and compilers to write efficient programs, but you'll also be able to understand which techniques to use and what to measure while improving performance. At its core, this book is about learning how to learn.
Table of Contents (18 chapters)
1
Section 1 – Performance Fundamentals
7
Section 2 – Advanced Concurrency
11
Section 3 – Designing and Coding High-Performance Programs

Measuring memory access speed

We have good evidence to assume that CPUs can operate much faster on the data already in registers compared to the data in memory. The specifications of the processor and memory speeds alone suggest at least an order of magnitude difference. However, we have learned by now not to make any guesses or assumptions about performance without verifying them through direct measurements. This does not mean that any prior knowledge about the system architecture and any assumptions we can make based on that knowledge are not useful. Such assumptions can be used to guide the experiments and devise the right measurements. We will see in this chapter that the process of discovery by accident can take you only so far and can even lead you into error. The measurements can be correct in and of themselves, but it is often hard to determine what exactly is being measured and what conclusions we can derive from the results.

It would seem that measuring memory access speed...