Elixirpi

This repository contains the Elixir program to calculate the value of pi to 10000 digits.

It uses a server node to distribute work and collect the results. It uses one or more worker nodes to do the calculation.

Setting up nodes to work accross the network

Make sure each machine that is to run a worker node has the same "erlang cookie" so that other nodes on the network can connect.

A cookie is a random string and is stored in the file .erlang_.cookie in the home directory. If you already have Elixir running on a machine, it might already have a .erlang.cookie file that can then be copied to each of the network hosts. In my case, copying the file from the MacOS machine to each of the hosts (alpha, beta, charlie and delta):

scp ~/.erlang.cookie pi@alpha:.erlang.cookie
scp ~/.erlang.cookie pi@beta:.erlang.cookie
scp ~/.erlang.cookie pi@charlie:.erlang.cookie
scp ~/.erlang.cookie pi@delta:.erlang.cookie

Install the dependency

This project uses the hex.pm module Decimals for the calculation of pi, to have an arbitrary precision for decimal numbers.

Run the following mix command to install the dependency:

mix deps.get

Compile and create an executable

Run the following mix command to create a "elixirpi" executable:

mix escript.build

Run the server node

The server node starts up a GenServer in the Elixirpi.Collector module.

Make sure the epmd daemon is running. This is the Erlang name server that will allow nodes to be named and look up other nodes on the network: epmd -daemon

Run the executable with the following switches, to start the server:

./elixirpi --mode=server [email protected]

Note: in the example above, the node name "[email protected]" uses the host name "gmac.local". Change the name value to match the host name of your machine.

When the server has no more work to be done, it will write the resulting value of pi to the file pi.txt

Run the worker node

The worker node will connect to a server node and requests work to be done (the work is a list of digit positions of pi to calculate). Once the worker calculated the result, it sends back the result to the server node and asks for the next chunk of work.

Make sure the epmd daemon is running. This is the Erlang name server that will allow nodes to be named and look up other nodes on the network: epmd -daemon

Run the executable with the following switches, to start the worker:

./elixirpi --mode=worker [email protected]

Note: in the example above, the node name "[email protected]" uses the host name "alpha.local". Change the name value to match the host name of your machine.

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Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/elixirpi.