Paratize
========
[](https://travis-ci.org/seantanly/elixir-paratize)
[](https://hex.pm/packages/paratize)
Elixir library providing some handy parallel processing facilities that supports configuring number of workers and timeout.
This library is inspired by [Parex](https://github.com/StevenJL/parex).
## Adding Paratize To Your Project
To use Paratize with your projects, edit your `mix.exs` file and add it as a dependency:
```
defp deps do
[
{:paratize, "~> x.x.x"},
]
end
```
## Examples
Paratize is designed to run slow tasks in parallel. There are two processor implementatons, first the chunk based implementation `Paratize.Chunk` and the second the pool worker based implementation `Paratize.Pool`. Both modules have the same API.
* `parallel_exec(fun_list, task_options)`
* `parallel_map(arg_list, fun, task_options)`
* `parallel_each(arg_list, fun, task_options)`
To execute a list of functions in parallel,
```
import Paratize.Pool
function_list = [
fn() -> Math.fib(40) end,
fn() -> :timer.sleep(5000) end,
fn() -> HTTPotion.get("http://wwww.reddit.com") end
]
parallel_exec(function_list) # => [102334155, :ok, %HTTPotion.Response{body...}]
function_keyword_list = [
fib: fn() -> Math.fib(40) end,
hang: fn() -> :timer.sleep(5000) end,
web_request: fn() -> HTTPotion.get("http://wwww.reddit.com") end
]
parallel_exec(function_keyword_list) # => [fib: 102334155, hang: :ok, web_request: %HTTPotion.Response{body...}]
```
To execute a map in parallel,
(useful when results are needed for further processing)
```
import Paratize.Pool
slow_func = fn(arg) -> :timer.sleep(1000); arg + 1 end
workload = 1..100
{time, result} = :timer.tc fn -> workload |> parallel_map(slow_func) |> Enum.join(", ") end
time # => 13034452 (8 CPU cores system, running 8 workers)
```
To execute a each in parallel,
(useful when resultset is large, and can be processed individually to prevent memory hog)
```
import Paratize.Pool
lots_of_urls |> parallel_each(fn(url) ->
HTTPotion.get(url) |> parse_page |> save_meta_data
end)
```
## Task Options
Each function accepts task options to customize the parallel processing.
* size - the number of parallel workers, defaults to the number of system cores given by `:erlang.system_info(:schedulers)`
* timeout - in milliseconds, the minimum time given for a function to complete, defaults to `5000`. If timeout happens, the entire parallel processing crashes with `exit(:timeout,...)`. To disable timeout, use `:infinity`.
## Considerations
To achieve maximum parallelism, `%Paratize.TaskOptions{}` size should be set to size of your workload,
```
alias Paratize.Pool
slow_func = fn(arg) -> :timer.sleep(1000); arg + 1 end
workload = 1..100
{time, result} = :timer.tc fn ->
workload |> Pool.parallel_map(slow_func, size: Enum.count(workload)) |> Enum.join(", ")
end
time # => 1004370 (Running 100 workers)
```
The `%Paratize.TaskOptions{}` timeout should not be relied upon for precise timing out of each workload, because it is not strictly enforced. It is an implementation detail that *reasonably* crashes the processor if no further work is completed after the timeout period has lapsed.
