randomHelpers

Arduino library for faster generation of random numbers.

Description

This library contains functions that have the goal to deliver random bits faster than the build in random function can, while still using it.

The idea is to have a buffer ( __randomBuffer) which can hold up to 32 bits. When a number of random bits are needed, these are first fetched from the buffer and if the buffer gets empty, it is filled again with a call to the random generator.

This strategy works well with a 32 bits buffer and requests for 1..16 random bits. However above 16 bits the overhead is larger than the gain. So to improve in that range too one could use a faster random function like the one from Marsaglia (included).

Note the gains differ per platform and are more explicit on the (slow) Arduino UNO platform than on a much faster ESP32.

This library relates to https://github.com/RobTillaart/Prandom

Interface

generators (sort of)

uint32_t Marsaglia() fast PRNG.
bool seedMarsaglia(uint32_t a, uint32_t b) seed the Marsaglia PRNG. a and b should not be 0. returns true on success.

getters (sort of)

bool getRandom1() returns 0 or 1, false or true.
uint8_t getRandom4() returns 0 .. 15.
uint8_t getRandom5() returns 0 .. 31.
uint8_t getRandom6() returns 0 .. 63.
uint8_t getRandom8() returns 0 .. 255 typically a byte.
uint16_t getRandom16() returns 0 .. 65535 (2 bytes).
uint32_t getRandom24() returns 0 .. 16777215 (3 bytes), e.g. random RGB colour.
uint32_t getRandom32() returns 0 .. 2^32 - 1 (4 bytes) this is the core random generator
uint64_t getRandom64() returns 0.. 2^64 - 1 (8 bytes).
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.

Typical wrappers.

bool flipCoin() A wrapper around getRandom1().
uint8_t throwDice() returns 1..6.

The examples show how to use these and how their performance gain relative to calling random() for every random number.

Performance

to elaborate

Operation

See examples

Future

must

improve/update documentation
- add performance figures

should

wrap all up in a class.
add JKISS? other RNG's

could

improve performance getRandomBits(n) for n = 17..31
investigate new tricks :)
test if the functions are uniform.
rename getRandom64() ==> get64() etc.
- when it is part of a class.
add getRandom2(), getRandom3(), getRandom12()?

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