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# Red Arrow CUDA - Apache Arrow CUDA Ruby

Red Arrow CUDA is the Ruby bindings of Apache Arrow CUDA. Red Arrow CUDA is based on GObject Introspection.

[Apache Arrow CUDA](https://arrow.apache.org/) is an in-memory columnar data store on GPU.

[GObject Introspection](https://wiki.gnome.org/action/show/Projects/GObjectIntrospection) is a middleware for language bindings of C library. GObject Introspection can generate language bindings automatically at runtime.

Red Arrow CUDA uses [Apache Arrow CUDA GLib](https://github.com/apache/arrow/tree/master/c_glib) and [gobject-introspection gem](https://rubygems.org/gems/gobject-introspection) to generate Ruby bindings of Apache Arrow CUDA.

Apache Arrow CUDA GLib is a C wrapper for [Apache Arrow CUDA C++](https://github.com/apache/arrow/tree/master/cpp). GObject Introspection can't use Apache Arrow CUDA C++ directly. Apache Arrow CUDA GLib is a bridge between Apache Arrow CUDA C++ and GObject Introspection.

gobject-introspection gem is a Ruby bindings of GObject Introspection. Red Arrow CUDA uses GObject Introspection via gobject-introspection gem.

## Install

Install Apache Arrow CUDA GLib before install Red Arrow CUDA. Install Apache Arrow GLib before install Red Arrow. See [Apache Arrow install document](https://arrow.apache.org/install/) for details.

Install Red Arrow CUDA after you install Apache Arrow CUDA GLib:

```text
% gem install red-arrow-cuda
```

## Usage

```ruby
require "arrow-cuda"

manager = ArrowCUDA::DeviceManager.new
if manager.n_devices.zero?
  raise "No GPU is found"
end

context = manager[0]
buffer = ArrowCUDA::Buffer.new(context, 128)
ArrowCUDA::BufferOutputStream.open(buffer) do |stream|
  stream.write("Hello World")
end
puts buffer.copy_to_host(0, 11) # => "Hello World"
```