add stypes.RandXorshift

[sh-mug]

stypes.RandXorshift

RandXorshift(reg_initval=0x12345678, dependency=None, enable=None, width=32)

Constructor Arguments

The input arguments of stypes.RandXorshift is as the following.

• reg_initval: initial value of the register. (optional, default value is 0x12345678)
• dependency: whether to set dependency between variables. (optional, the default value is None)
• enable: enable flag. (optional, the default value is None)
• width: data width (optional, the default value is 32, and 32 or 64 can be set)

The reset input is intentionally omitted to prevent this function from exhibiting deterministic behavior for large unit operations (e.g., iterations of batch learning).

Implementation

The RandXorshift class implements hardware random number generation using the Xorshift algorithm on embedded systems. The Xorshift algorithm is a pseudo-random number generator that utilizes simple bitwise operations to generate a sequence of seemingly random numbers.

To implement the RandXorshift class, I refer to Marsaglia's paper 'Xorshift RNGs' (2003) and update the values according to the data width, as shown in the pseudo-code below. I treat state variables and outputs only as unsigned integers to ensure accurate Xorshift-based pseudo-random number generation implementation, following the paper's method.

Case for 32-bit data width

uint32_t next(uint32_t x) {
  x ^= (x << 13);
  x ^= (x >> 17);
  x ^= (x << 5);
  return x;
}

Case for 64-bit data width

uint64_t next(uint64_t x) {
  x ^= (x << 13);
  x ^= (x >> 7);
  x ^= (x << 17);
  return x;
}

Test

Referring to the test of stypes.Counter, I added stream_rand_xorshift and verified whether the pseudo-random number sequence output by stypes.RandXorshift matches the expectation.