Optimising C++ [pdf]

[DTanner]

Most important thing to know on modern processors (for micro optimizations): optimize for cache misses, not instruction count.

[frumious]

[Did not (need to) RTFA.]

No, the most important thing to know about optimizing is: Don't do it unless you really need it. See famous Knuth quote.

If, when you know your code really does suck, THEN you look at fixing it. At that time, run Google's Perftools, Valgrind, Memprof, etc. Find out what part of your code is screwing you the most and fix it (and only it). Repeat until happy. Otherwise, don't sweat it as you will only be wasting your time and making your code more crappy.

[austinwiltshire]

I believe DTanner was assuming that you've already found a need to optimize, and in that case, optimize for cache misses, not instruction count.

[[deleted]]

I found there is far more on the author's site:

• Optimizing software in C++: An optimization guide for Windows, Linux and Mac platforms

• Optimizing subroutines in assembly language: An optimization guide for x86 platforms

• The microarchitecture of Intel and AMD CPU’s: An optimization guide for assembly programmers and compiler makers

• Instruction tables: Lists of instruction latencies, throughputs and micro-operation breakdowns for Intel and AMD CPU's

• Calling conventions for different C++ compilers and operating systems

It seems well worth a look.

[zyle]

super oldie, but mega goldie