o-ogod-those-odds

uses the rayon crate for parallelization and rand to preform 1,000,000 double coin flips in 1,283,788.75 ns.

Multithreading

The ParallelIterator::map_init method allows us to reuse ThreadRng between iterations. Each thread calls the init function to get an instance of ThreadRng to use when calling the map_op function

Binary ops

The ThreadRng random number generator produces integers where each bit has an equal chance of being 1 or 0, this can be leveraged to maxamize the amount of moves preformed per call. Each integer is divided into two 32 bit parts which are anded together the result is a 32 bit integer where each bit has a 1/4 chance of being 1, by using the popcnt assembly operation 32 moves can be calculated all at once. This means all required moves can be calculated with 8 calls to Rng::gen (7 * 32 = 224, plus one for the remaining 7).

And truth table
    ┌───┬───┐
    │ 0 │ 1 │
┌───┼───┼───┤
│ 0 │ 0 │ 0 │
├───┼───┼───┤
│ 1 │ 0 │ 1 │
└───┴───┴───┘

Assembly

For some reason preforming the shifting in an assembly block makes this algorithm faster. This could be due to a reduced number of branches.

Proof