Difference between revisions of "Performance optimization"
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Revision as of 2013-10-30T20:29:11
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.
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.
Here is an example :
#define ledPin 13
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 :