Subject: Re: [Boost-users] proto for array expressions
From: Eric Niebler (eric_at_[hidden])
Date: 2008-12-18 19:45:35
James Sutherland wrote:
>
> On Dec 18, 2008, at 3:46 PM, Eric Niebler wrote:
>
>> Daniel Oberhoff wrote:
>>> Now with proto I was wondering how hard it would be to build an et
>>> engine for array math. Basically I am interested in general tensor
>>> notation, and the resulting expressions should be iteratable
>>> efficiently. think (advanced example):
>>> a_ij = b_i * (c_j - sum(d_ijk, k = [i-1,1])
>>
>> I don't understand your notation. What are a_ij et. al.?
>>
> Presumably Einstein notation:
> a_i = vector
> a_ij = 2D matrix
> a_ijk = 3D array
> so that
> b_i c_j
> is the outer product of two vectors, producing a matrix...
I guess I'm dense, but I still don't get it. What does this expression mean?
a_ij = b_i * (c_j - sum(d_ijk, k = [i-1,1])
At any rate, it requires a domain expert to say how hard it would be to
implement a given DSEL, and I'm not a linear algebra domain expert. I've
done my best to document Proto extensively, and I can answer questions
about Proto but not about linear algebra.
-- Eric Niebler BoostPro Computing http://www.boostpro.com