ParasCoin

Paras (पारस) (pārasa paarasa) the hindi word equivalent of midas or the philosopher's stone

This project creates a cryptocurrency miner network that looks for strings whose SHA256 has k leading zeros, k being fixed for each network

Building the code

Use mix escript.build to generate a local escript binary called paras

Note about running the code

To run this application EPMD must be running as a daemon, run epmd -daemon before starting the application to avoid errors like:

** (FunctionClauseError) no function clause matching in :erlang.set_cookie/2

Discussion

1. Work unit size: Each node has 10 * num_logical_processors workers, all of which recieve messages to process disjoint blocks of size 1024. I found that using a large number of workers in each node was better because:

   • There is always at least one process mining a range even when some other process has completed its share and is dealing with network IO for sending messages.
   • Smaller work unit sizes with larger process pools enable maintaing a more fine-grained save state should the server ever crash. This means that too many old messages are not repeated should the server ever respawn with a previously known good state

2. Output of ./paras 4:

$ ./paras 4
vyenaman;7P33   0000d9d41ef9a43600d7b68d5da894a3a742ab3d537ab2b891c9495615d462d3
vyenaman;9jf    0000c579d6e3192f246c878f4677009b43810f1eb226d00d13105df1f81ef1e1
vyenaman;13wW   00005c23b92b2014fa7f1e5b23d8e439b6e8bd062552329e743d59c9ca15ccd6
vyenaman;38Gc   00005e2ca9dc57215e6b7b0a0a71789cc5f344da7c8d86a91008e5be5e1a97c1
vyenaman;23kG   0000c3119ef5acf8544fb171901e89304792ba5e0a72ab633b5f97906395d125
vyenaman;44hq   0000f9f0ff04a46c936daad283bb00d235166a60d696e6278927df843b708f41
vyenaman;1yZI   0000b0ca35d295506dcc276c02678e07a3f673eafd5971ea813218a3cdc45236
vyenaman;3vdy   00001e8148d1064236c27b732db94f35bb29aedd3f03c23a7e4769d2713b3149
vyenaman;jIG    000020da1264d27e70445c34d8ffb2135f5868adb984c4bf543f3dfbde42a5d7
vyenaman;3nTq   000063a8b050ec898693210429ad6b4a19ea7309343b8dd60d502786014f76fc
vyenaman;20Ot   00009952cccea79519607608f20c03d9446e4181f7350ceb353e4f9409621250
vyenaman;1mAC   0000a6c23fd7e2bee126422e93ad70ea27c7ebce3136096b5ef6caecf976ddfe
vyenaman;1xsE   0000f29d6f8592ad49a03fa468d107d6f4c9723bb1e97fba26af203742e31a9c
vyenaman;d5x7   00002dd38f58c64e7a2edb2d0ee887c6d791199ef82a5e3720d899d67e15c6d0

3. Running time of ./paras 4 with CPU and Real time ratios: I ran the binary for exactly 60s (using the timeout command) to get the following results:

$ time timeout -sHUP 60s ./paras 4 > /dev/null

real    1m.009s
user    7m47.740s
sys     0m2.700s

• The ratio of CPU time to REAL time is: 467 / 60 ~ 7.78

5. Coin with most zeros:
   • 7 leading zeros: vyenaman;kZP1E
6. Largest number of working machines in the network:
   • 8 machines, each with 8 cores

Architecture

This section talks about the high level structure of the network and what summarizes the message passing scheme used.

• There is a single globally named process that manages all worker nodes and itself called the MiningServer which is a GenServer with the name {:global, :mining_server}
  • This node is singluar in the network and responsible for distributing work among its children which are the process pool managers from remote nodes
• Each node has a locally named process pool backed by the GenServer MinerPool, which recieves work messages from the master node MiningServer and translates them appropriately for its children to do work with. All commuincation is async with a callback to a master node's listening process
• The leaf in this tree of messages is a Miner node which does the real heavy lifting in computing the SHA256 of a range of numbers to find valid coin-strings

Drawn as a tree, the network looks like so (arrows indicate flow of messages)

                  MiningServer
                      |
                      V
------------------------------------------------------
|(Node1)     | (Node2)    | (Node 3)   ... | (Node n)
|->MinerPool |->MinerPool |->MinerPool     |->MinerPool
  |->Miner     |->Miner     |->Miner         |->Miner
  |->Miner     |->Miner     |->Miner         |->Miner
  ...          ...          ...              ...
  |->Miner     |->Miner     |->Miner         |->Miner
  ---------------------------------------------------
                      |-> MiningServer

Decisions

This section goes over the various decisions that were made with regards to ambiguities in the project description:

• Coin format: <gator_id>;<base62_suffix>

• Space enumeration: The server linearly enumerates over the space in blocks of size 1024, I found this to be a good value to use for local and remote nodes so that processes are almost always occupied

• Node connectivity: The application relies on the Node library that elixir ships with. EPMD must be started as a background process before running this code. To do so, run epmd -daemon in the shell session before running the project's binary