mmap-ipc

IPC programming exercise using memory mapped file(s).

Spec

Create two small applications: one called Randomizer; the other, Prime.

Randomizer‘s job is to generate a series of positive random integers and send those to Prime via a distributed queue of integers.

Prime's job is to receive the integers, calculate whether the integer is a prime or not, and return the answer to Randomizer via a distributed queue that contains the original number and a Boolean -which Randomizer will print to the console.

Use only the standard java library
Both applications will run on the same host
The system should be as fast as possible
The results do not have to be returned in the same order as received

Implementation Notes:

IPC via shared memory is a sensible choice because both Randomizer and Prime processes run on the same host.

To build and run:

mvn clean install
cd classes/
java jdc.Prime
java jdc.Randomizer

Randomizer

As per 'spec', Randomizer has the following responsibilities:

add positive integers to a queue
read answers from a queue

These responsibilities are unit tested separately from those of its dependencies.

Prime

As per 'spec', Prime has the following responsibilities:

read positive integers from a queue
add primality-tested answers to a queue

Like Randomizer, Prime's responsibilities are unit tested separately from those of its dependencies.

Queue reader and writer are separate for illustration convenience and testability.

Performance Notes

Prime lags Randomizer due to its more computationally expensive primality test.

If Prime is considered a performance bottleneck, after improving the low hanging fruit (e.g.: calculate MAX_INT primes offline and load upfront, etc) and after careful performance analysis, techniques such as batching and/or calculating several primes in parallel can be implemented and tested, e.g.:

Stream.generate(intsQueue::poll)
.filter(Objects::nonNull)
.parallel()
.forEach(i -> {
    Answer answer = primality.apply(i);
    answersQueue.add(answer); // Queue implementation should change to accommodate multiple writers
});