I trying to implement cross-platform consistent random number generation with a 32-bit seed. Most post point me to Mersenne Twister or writing my own implementation.
In the source code there is a function called void init_by_array().
Is the only purpose of this function to extend the seed passed 32-bit?
From the ReadMe
init_by_array(init_key, key_length) initializes the state vector by using an array init_key[] of unsigned 32-bit integers of length key_kength. If key_length is smaller than 624, then each array of 32-bit integers gives distinct initial state vector. This is useful if you want a larger seed space than 32-bit word.
Failing to understand this just assuming based on the last sentence.
The code seems to run fine only using init_genrand() and seems to be producing consistent results.
Mersenne Twister has 19937 bits of state space that it uses to iterate through the sequence of values it produces. If you initialize it with a 32 bit integer, you are restricting it to just 232 out of the 219937 possible starting points, and there are a massive number of sample trajectories that you will never see. The init_by_array() function allows you to specify more bits for the initial state, giving the potential to achieve any of the sampling trajectories which MT is capable of generating.