[libre-riscv-dev] 3D Matrix-style operations / primitives

[Hendrik Boom]

On Tue, Sep 17, 2019 at 10:24:27PM -0700, lkcl wrote:
> does anyone know of some mathematics for analysing which would be the best 
> "primitives" for Matrix operations, suited to transposition and inversion, 
> determinant and normalisation?
> 
> for 3D that generally means just 2x2, 3x3 and 4x4.
> 
> i'm looking up how matrix inverses are calculated and, hoo-boy :)
> https://integratedmlai.com/matrixinverse/
> https://www.wikihow.com/Find-the-Inverse-of-a-3x3-Matrix

What I remember from my numerical analysis course long long ago is that
calculating a matrix inverse is almost *never* the right thing to do.  
Usually there are completely diffeent algorithms that do what you 
wanted the matric inverse for that are much more accurate.

LU-decomposition is one of these tools -- finding an lower-triangular 
matrix and a upper-triangular matrix whose product is the original 
matrix.

But I don't remember much more than that.

-- hendrik