Implement fast matrix encoding

[lrq3000]

Implement fast matrix encoding

[hidde-jan]

The only thing I don't understand is how the init table is generated with this approach.

The matrix is generated by first generating a Vandermonde matrix where the alpha_i's are taken as some Galois exponents. Since it is a Vandermonde matrix, any square matrix whose rows are (distinct) rows of this Vandermonde matrix is invertible. They then postmultiply this matrix by the inverse of the top n-rows such that the top of the resulting matrix is the Identity matrix.

[lrq3000]

@hidde-jan thank you very much for the explanation! I will try to implement an encoder/decoder like this :-) Do you know whether this method is significantly faster than looping? (I guess it is because then the operations are vectorized and leveraging BLAS fast calculations?)