Add FC

optimization.md

@@ -1,10 +1,8 @@
 # Optimization
 
-Optimization means making a program more efficient in terms of some metric such as speed or memory usage (but also others such as power consumption, network usage etc.) while preserving its functionality.
+Optimization means making a program more efficient in terms of consumption of some computing resource or by any similar metric, commonly aiming for greater execution speed or lower memory usage (but also e.g. lower power consumption, lower network usage etc.) while preserving how the program functions externally. Unlike [refactoring](refactoring.md), which aims primarily for a better readability of source code, optimization changes the inner behavior of the executed program to a more optimal one.
 
-Unlike [refactoring](refactoring.md), optimization changes the behavior of the program to a more optimal one (but again, it doesn't change its functionality).
-
-## General Tips'n'Tricks
+## General Tips'N'Tricks
 
 These are mainly for [C](c.md), but may be usable in other languages as well.
 
@@ -30,11 +28,12 @@ These are mainly for [C](c.md), but may be usable in other languages as well.
 - Search literature for **algorithms with better [complexity class](complexity_class.md)** (sorts are a nice example).
 - For the sake of embedded platforms **avoid [floating point](floating_point.md)** as that is often painfully slowly emulated in software. Use [fixed point](fixed_point.md).
 - **Early branching can create a speed up** (instead of branching inside the loop create two versions of the loop and branch in front of them). This is a kind of space-time tradeoff.
+- **You can optimize critical parts of code in [assembly](assembly.md)**, i.e. manually write the assembly code that takes most of the running time of the program, with as few and as inexpensive instructions as possible (but beware, popular compilers are very smart and it's often hard to beat them). But note that such code loses portability! So ALWAYS have a C (or whatever language you are using) [fallback](fallback.md) code for other platforms, use [ifdefs](ifdef.md) to switch to the fallback version on platforms running on different assembly languages.
 
-## When to Actually Optimize?
+## When To Actually Optimize?
 
 Nubs often ask this. Generally fine, sophisticated optimization should come as one of the last steps in development, when you actually have a working thing. These are optimizations requiring significant energy/time to implement -- you don't want to spend resources on this at the stage when they may well be dropped in the end, or they won't matter because they'll be outside the bottleneck. However there are two "exceptions".
 
-The highest-level optimization is done as part of the initial design of the program, before any line of code gets written. This includes the choice of data structures and mathematical models you're going to be using, the very foundation around which you'll be building your castle. This happens in your head at the time you're forming an idea for a program, e.g. you're choosing between [server-client](server_client.md) or [P2P](p2p.md), [monolithic or micro kernel](kernel.md), [raytraced](ray_tracing.md) or [rasterized](rasterization.md) graphics etc. These choices affect greatly the performance of your program but can hardly be changed once the program is completed, so they need to be made beforehand. **This requires wide knowledge and experience**.
+The highest-level optimization is done as part of the initial design of the program, before any line of code gets written. This includes the choice of data structures and mathematical models you're going to be using, the very foundation around which you'll be building your castle. This happens in your head at the time you're forming an idea for a program, e.g. you're choosing between [server-client](server_client.md) or [P2P](p2p.md), [monolithic or micro kernel](kernel.md), [raytraced](ray_tracing.md) or [rasterized](rasterization.md) graphics etc. These choices affect greatly the performance of your program but can hardly be changed once the program is completed, so they need to be made beforehand. **This requires wide knowledge and experience** as you work by intuition.
 
-Another kind of optimization done during development is just automatically writing good code, i.e. being familiar with specific patterns and using them without much thought. For example if you're computing some value inside a loop and this value doesn't change between iterations, you just automatically put computation of that value **before** the loop. Without this you'd simply end up with a shitty code that would have to be rewritten line by line at the end.
+Another kind of optimization done during development is just automatically writing good code, i.e. being familiar with specific patterns and using them without much thought. For example if you're computing some value inside a loop and this value doesn't change between iterations, you just automatically put computation of that value **before** the loop. Without this you'd simply end up with a shitty code that would have to be rewritten line by line at the end. Yes, compilers can often do this simple kind of optimization for you, but you don't want to rely on it.