Re: Using ruby for scientific computing

Hello,

On 8 =CE=A3=CE=B5=CF=80 2012, at 18:06 , Olivier Saut =
<[e-mail]> wrote:

> Hi all,
>=20
> For pedagogic purposes, I am trying to solve simple partial =
differential
> equations (say a diffusion equation on a regular mesh in 2D) with =
Ruby.
> Using the NArray gem, I have built a satisfactory tool from an =
interface
> (and ease of use) point of view but the performance are suboptimal.=20

Is the code available on a public repo?

> I am now wondering what is the right way to improve my code
> performance-wise. I am doing a lot of matrix-vector and vector-vector
> products.=20
>=20
> =46rom 2 2D NArrays describing two scalar fields, dot-product is =
implemented as :
>=20
> def dot_product(vec_a, vec_b)=20
>        dot_product=3D(vec_a*vec_b">vec_a*vec_b).sum=20
> end
>=20
> and as I am working with sparse matrices, (for the time being) a =
matrix
> is an Array of Hashes. Each key of the hash contains the index of the
> non-vanishing coefficients (the value of this coefficient is the value
> of the Hash) of the matrix. For the identity matrix it gives
>=20
> def identity(sizeX, sizeY)
>        mat=3D[]
>        (0..sizeX*sizeY">sizeX*sizeY).each { |ind|
>            mat << {ind=3D>1.0}
>        }
>        mat
> end
>=20
>=20
> Matrix vector product is then defined as
>=20
> def matrix_vector_product(mat, vector)=20
>        ff=3DNArray.float(100,100)
>        (0..100*100).each { |ind|
>            matrix[ind].each do |key,value|
>                ff[[ind]]+=3Dvalue*vector[[key]][0]
>            end
>        }
>        ff
> end
>=20
> I am wondering what is the best way to tackle this performance problem =
:
> 1. Improve the ruby code (and how? :) Should I avoid using hashes?
> 2. Write an extension to perform these operations in C. BTW is there a
> way to access directly NArray data (without copy) from a C extension?
> 3. Use a wrapper like Ruby-lapack
> (
> https://rubyforge.org/projects/ruby-lapack/
> ).
>=20
> What do you think?=20
>=20
> Thanks for your help !
>=20
> --=20
>  Olivier Saut
>=20
> [e-mail]
> 						       	                	=
- Olivier
>=20
>=20


Panagiotis Atmatzidis
-----------------------------
Pharmacy Student at VFU

email4lists: 	[e-mail]
More info: 	http://about.me/atmosx

The wise man said: "Never argue with an idiot, he brings you down to his =
level and beat you with experience."