I need a very simple pseudo random generator (no any specific quality requiremen

Question

I need a very simple pseudo random generator (no any specific quality requirements) and I found Microsoft's variant of LCG algorithm used for rand() C runtime library function fit my needs (gcc's one seems too complex).

However, I worry the algorithm (including its "magic numbers" i.e coefficients) may by patented or restricted for use in some another way.

Is it allowed to use this algorithm without any licence or patent restrictions or not?

I can't use library rand() because I need my results to be exactly reproducible on different platforms

Explanation / Answer

The Mersenne twister prng is well known and implemented.

For an even simpler approach, Project Euler has used a pseudo random number generator:

S0 = seed

Sn+1 = Sn2 mod 50515093

If you want something close to 2^32, change the mod to 0xFFFFFFFB (the number 4,294,967,291 - the largest 32 bit prime)

The man page for rand has the following implementation from the POSIX.1-2001 specification:

static unsigned long next = 1;

/* RAND_MAX assumed to be 32767 */
int myrand(void) {
next = next * 1103515245 + 12345;
return((unsigned)(next/65536) % 32768);
}

void mysrand(unsigned seed) {
next = seed;
}
Look at the Art of Computer programming, volume 2 - it has a section dedicated to random number generation.

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