parallel_map

Note: This package only works for the erlang target.

This is a simple gleam library that adds a iterator_pmap and list_pmap, which has a similar behaviour and interface as iterator.map and list.map, except it runs in parallel by spawning extra processes to do the work.

There is also iterator_find_pmap and list_find_pmap which stop the whole parallel execution after finding the first Ok value.

gleam add parallel_map

import gleam/list
import gleam/iterator
import gleam/result
import parallel_map.{MatchSchedulers, WorkerAmount}

pub fn main() {
  let map_func = fn(a: Int) -> Int {a * a}

  let iterator_input = iterator.range(0, 1000)

  iterator_input
  |> iterator.map(map_func)

  // can be rewritten as
  iterator_input
  |> parallel_map.iterator_pmap(map_func, WorkerAmount(16), 100)
  |> iterator.map(result.unwrap(_, -1))

  let list_input = list.range(0, 1000)

  list_input
  |> list.map(map_func)

  // can be rewritten as
  list_input
  |> parallel_map.list_pmap(map_func, MatchSchedulersOnline, 100)
  |> list.map(result.unwrap(_, -1))


  // there is also
  //   parallel_map.iterator_find_pmap similar to iterator.find_map
  //   parallel_map.list_find_pmap similar to list.find_map,
  // which stop the works after finding the first Ok value.

  let find_map_func = fn(a: Int) -> Result(Int, Int) {
    case a {
      x if x > 500 -> Ok(x * 2)
      _ -> Error(a)
    }
  }

  iterator_input
  |> iterator.find_map(find_map_func)

  // can be rewritten as
  iterator_input
  |> parallel_map.iterator_find_pmap(find_map_func, WorkerAmount(16), 100)


  list_input
  |> list.find_map(find_map_func)

  // can be rewritten as
  list_input
  |> parallel_map.list_find_pmap(find_map_func, MatchSchedulersOnline, 100)
}

Further documentation can be found at https://hexdocs.pm/parallel_map.

Development

gleam run   # Run the project
gleam test  # Run the tests
gleam shell # Run an Erlang shell