Re: [eigen] ISO C++ working groups on Linear Algebra / Machine Learning

[Peter <list@xxxxxxxxxxxxxxxxx>]

Dear Francois Fayard,


Am 16.02.19 um 14:19 schrieb Francois Fayard:

> - Once those data structures are built, we need linear algebra for those who need it.
> I personally like the dot function that can do the following thing : y = dot(A, x) or C = dot(A, B). The first operation does a “matrix


In my opinion, provided we just need a single matrix-matrix multiplication, like C = dot(A, B),
the notation doesn't matter. However, for more complicated expressions, e.g.

 A * ( D +  C * E * B + B * E * C)

a 'star' like notation is much simpler to verify for correctness, I can just
copy from my LaTeX documentation,  than something like

dot( A, D + dot( C , dot (E, B) + dot( B, dot(E,C))))

e.g. I don't need so many braces.

I do agree that in the case that you pointed out as your main work case, namely speeding up code, the notation
is not that important, as you anyway want to take control over all the details, like the way temporaries are used.
However, first you need a correct implementation. And in this regime I find the notation in Eigen very helpful.

Best regards,
Peter