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109 lines
3.6 KiB
Markdown
109 lines
3.6 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/randomHelpers/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/randomHelpers/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/randomHelpers/blob/master/LICENSE)
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[](https://github.com/RobTillaart/randomHelpers/releases)
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# randomHelpers
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Arduino library for faster generation of random numbers.
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## Description
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This library contains functions that have the goal to deliver random bits faster
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than the build in random function can, while still using it.
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The idea is to have a buffer ( __randomBuffer) which can hold up to 32 bits.
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When a number of random bits are needed, these are first fetched from the
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buffer and if the buffer gets empty, it is filled again with a call to the
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random generator.
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This strategy works well with a 32 bits buffer and requests for 1..16 random bits.
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However above 16 bits the overhead is larger than the gain.
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So to improve in that range too one could use a faster random function like the one
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from Marsaglia (included).
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Note the gains differ per platform and are more explicit on the (slow) Arduino UNO
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platform than on a much faster ESP32.
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This library relates to https://github.com/RobTillaart/Prandom
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## Interface
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```cpp
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#include "randomHelpers.h"
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```
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#### generators (sort of)
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- **uint32_t Marsaglia()** fast PRNG.
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- **bool seedMarsaglia(uint32_t a, uint32_t b)** seed the Marsaglia PRNG. a and b should not be 0. returns true on success.
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#### getters
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- **bool getRandom1()** returns 0 or 1, false or true.
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- **uint8_t getRandom2()** returns 0 .. 3.
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- **uint8_t getRandom3()** returns 0 .. 7.
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- **uint8_t getRandom4()** returns 0 .. 15.
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- **uint8_t getRandom5()** returns 0 .. 31.
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- **uint8_t getRandom6()** returns 0 .. 63.
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- **uint8_t getRandom7()** returns 0 .. 127.
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- **uint8_t getRandom8()** returns 0 .. 255 typically a byte.
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- **uint16_t getRandom16()** returns 0 .. 65535 (2 bytes).
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- **uint32_t getRandom24()** returns 0 .. 16777215 (3 bytes), e.g. random RGB colour.
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- **uint32_t getRandom32()** returns 0 .. 2^32 - 1 (4 bytes) this is the core random generator
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- **uint64_t getRandom64()** returns 0.. 2^64 - 1 (8 bytes).
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- **uint32_t getRandomBits(n)** returns 0.. 2^n - 1 This works well for 1..16 bits but above 16 it is slower than the standard way.
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#### Typical wrappers.
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- **bool flipCoin()** A wrapper around getRandom1().
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- **uint8_t throwDice()** returns 1..6.
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The examples show how to use these and how their performance gain relative to
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calling **random()** for every random number.
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## Performance
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to elaborate
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## Operation
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See examples
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## Future
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#### Must
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- improve/update documentation
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- add performance figures
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- wrap all up in a class.
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- rename getRandom64() ==> get64() etc.
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#### Should
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- improve performance getRandomBits(n) for n = 17..31
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- how to preserve bits if idx too small.
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- add JKISS? other RNG's
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- test if the functions are uniform.
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#### Could
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- improve performance getRandomBits(n) for n = 17..31
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- investigate new tricks :)
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- add **getRandom9() 10()** can be done 3x from 32 bits.
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- 11..16 => 2x from 32 bits
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-
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- add **getRandom12()** clipping get16 is equally fast.
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#### Wont
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