### Lab 6: Erlang Concurrency

Due Friday, December 3rd at 11:59pm.

Work in groups of 2 or 3.

#### Problem 1

Write an Erlang distributed program for factoring an integer number. More specifically, given a number N, you need to check all possible divisors of N between 2 and sqrt(N).

The process starts with a control thread that spawns processes to check separate ranges for possible factors: each process gets a range of numbers to check (i.e. it gets sent N, the minimum, and the maximum of the range). The control processes then is prepared to receive a message from the other processes. It keeps the list of PIDs of the processes (or just the number of processes).

If a process discovers a factor, it sends that information back to the control process. Otherwise it sends an atom indicating that there are no factors of N in the range.

The control process outputs the factors if they are found or waits until all the processes finish without finding a factor, in which case it outputs that the nubmer is prime.

Use Prime numbers archive to generate test data. Use at least one large prime number and at least one product of two large primes (7-8 digit values of N will do for starters). Check how the program performs for different range sizes.

#### Problem 2

Write a program that does the following:

1. The strating process spawns N processes. Each process gets a process id of the previous process and a random number.
2. The processes communicate to each other trying to determine the largest of the random numbers.
3. After R rounds of message passing the processes output what they discovered as the largest number. Not all of them may have detected the largest number; that's OK.
4. You might want to experiment with N and R and see how accuracy improves with more messages.

UMM CSci 4409

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