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

Summary

In this chapter, we have learned about the C++ memory model and the guarantees it gives to the programmer. The result is a thorough understanding of the low level of what happens when multiple threads interact through shared data.

In multi-threaded programs, unsynchronized and unordered access to memory leads to undefined behavior and must be avoided at any cost. The cost, however, is usually paid in performance. While we always value a correct program over an incorrect but fast one, when it comes to memory synchronization, it is easy to overpay for correctness. We have seen different ways to manage concurrent memory accesses, their advantages, and tradeoffs. The simplest option is to lock all accesses to the shared data. The most elaborate implementation, on the other hand, uses atomic operations and restricts memory order as little as possible.

The first rule of performance is in full force here: performance must be measured, not guessed. This is even more important...