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# in_threads

Easily execute Ruby code in parallel.

```ruby
urls.in_threads(20).map do |url|
  HTTP.get(url)
end
```

## Installation

Add the gem to your Gemfile...

```ruby
gem 'in_threads'
```

...and install it with [Bundler](http://bundler.io).

```sh
$ bundle install
```

Or, if you don't use Bundler, install it globally:

```sh
$ gem install in_threads
```

## Usage

Let's say you have a list of web pages to download.

```ruby
urls = [
  "https://google.com",
  "https://en.wikipedia.org/wiki/Ruby",
  "https://news.ycombinator.com",
  "https://github.com/trending"
]
```

You can easily download each web page one after the other.

```ruby
urls.each do |url|
  HTTP.get(url)
end
```

However, this is slow, especially for a large number of web pages. Instead,
download the web pages in parallel with `in_threads`.

```ruby
require 'in_threads'

urls.in_threads.each do |url|
  HTTP.get(url)
end
```

By calling `in_threads`, the each web page is downloaded in its own thread,
reducing the time by almost 4x.

By default, no more than 10 threads run at any one time. However, this can be
easily overriden.

```ruby
# Read all XML files in a directory
Dir['*.xml'].in_threads(100).each do |file|
  File.read(file)
end
```

Predicate methods (methods that return `true` or `false` for each object in a
collection) are particularly well suited for use with `in_threads`.

```ruby
# Are all URLs valid?
urls.in_threads.all? { |url| HTTP.get(url).status == 200 }

# Are any URLs invalid?
urls.in_threads.any? { |url| HTTP.get(url).status == 404 }
```

You can call any `Enumerable` method, but some (`#inject`, `#reduce`, `#max`,
`#min`, `#sort`, `#to_a`, and others) cannot run concurrently, and so will
simply act as if `in_threads` wasn't used.

## Copyright

Copyright (c) 2010-2017 Ivan Kuchin. See LICENSE.txt for details.