Difference between revisions of "Performance optimization"

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(Minimum variables size)
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== System specific optimization ==
 
== System specific optimization ==
  
=== Minimum variables size ===
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=== Variables ===
  
 
==== data types ====
 
==== data types ====

Revision as of 2013-10-30T19:23:47

Introduction

Gamebuino is a video game console which has limited hardware (8-bits CPU running at 16Mhz and 2KB of RAM...). It's far enough if you want to program Pong or Tetris, but if you plan to do some advanced games with multiplayer and artificial intelligence, you will probably have to optimize your game for it to run fast enough and fit in the chip's memory.

Most of the optimization work is done at high level, by using smart algorithms. But sometimes it's not enough, and to go further you have to get into more system-specific programming to gain speed and memory usage.

General optimization

Premature optimization

Don't optimize something that doesn't need to be. First write a clean code, something easy to read and maintain. Then, only if you actually need performance improvement, benchmark your code to know what is most time consuming and likely to be optimized. Don't try to guess what should be optimized, because you'll be wrong most of the time, and you'll spend time optimizing something that isn't the bottleneck.

Don't be smart

"You should think REALLY, REALLY hard about sacrificing code clarity for the sake of speed or space." westfw on Arduino forum

Other tips & tricks

System specific optimization

Variables

data types

You should always use the smallest variable type you need. Because Gamebuino runs on a 8-bits microcontroller, 16 and 32 bits variables takes a lot of time and memory, and floating point variables are even worse than integers.

Arduino variable types
Type Min Max Size Perf
byte 0 255 8  :)
char -128 127 8  :)
unsigned int 0 65 535 16  :/
int −32 768 32 767 16  :/
unsigned long 0 4,294,967,295 32  :(
long -2,147,483,648 2,147,483,647 32  :(
float / double -3.4028235E+38 3.4028235E+38 32  :'(

For more information about the data type refer to Arduino Reference.

#define

You can use #define for constant variables that will never change, like pin numbers. This way it won't take any space in the chip's memory.

progmem

For constant large arrays or bitmaps you can use progmem to avoid loading them in the RAM. Arduino article explains that, for more info read a complete tutorial.

Loops

SPI

I2C / TWI

Clock frequency

Assembly language

Other tips & tricks

References

For further information, you can read the following :