I just came across the NArray library for Ruby -- please excuse my ignorance when asking this question :)
What are the advantages of using the NArray library over the standard Ruby Array implementation?
I've seen that NArray is geared towards numerical computing, but looking at the API, it looks like there are only a few extensions over Array geared towards numerical values -- nothing that you couldn't do with Array..
- Why not just use Array?
- Is there a huge speed advantage?
- Is there a huge memory advantage?
- Any other advantages over using the regular Ruby Array class?
Google didn't really come up with a useful explanation of this question.
References I found:
http://rubydoc.info/gems/narray-ruby19/0.5.9.7/NArray
For large typed array creation NArray can be faster, though for small array creation (e.g. for temporary intermediate objects) Ruby Array seems to be fast is faster.
Benchmark code:
Results:
You are missing the most important point:
NArray
is not just extended for numerical processing, it is also restricted. In particularNArray
elements can only be fixed-size integers or floatsNArray
s themselves are also fixed-size, they cannot shrink or growAn implementation of
NArray
can exploit those restrictions to provide superior performance.See also the slide about NArray: http://www.slideshare.net/masa16tanaka/narray-and-scientific-computing-with-ruby
No, it's completely different from Array. NArray has many numerical functions and multi-dimensional features. On the other hand, NArray is static; it does not have push/pop methods, etc. NArray's method list is http://narray.rubyforge.org/SPEC.en
Array holds Ruby Objects. It is inefficient to hold numerical values.
Yes. p.36 of the above slide shows NArray is up to 50 times faster.
Note that Array is faster than NArray if the loop is written in Ruby.
Yes. As for Float values, Array consumes about 4 times more memory than NArray on my 64bit Linux machine.