Matrices stored in column-major format?

[ocharles]

What exactly is the question here? If you're sending matrices to OpenGL there are flags to convert on the fly. If you need column major somewhere else - where exactly do you need it? Manually specifying matrices? Loading from files?

On Fri, 6 Nov 2015 5:51 pm Alex Lang notifications@github.com wrote:

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[alang9]

I'm thinking of what to do if you want to perform matrix multiplication using BLAS' dgemm.

• You could transpose the matrices to the orientation you want by using distribute, but this seems unnecessarily slow.
• You can have your multiplication function accept extra in flags to specify if you want to transpose each of your input matrices, but this means you need 2 extra arguments, and it's harder to write the type signature for such a multiplication function
• or you could have a flag in your data type to specify if your Matrix is column-major or row-major, and being able to transpose in O(1) by flipping the flag instead of using distribute. This seems the most convenient for me, and hmatrix does something similar.

[ekmett]

Thinking outloud here.

Right now, dgemm, etc. are all going to require us to marshal to an external format regardless unless we do something like #152 to allow us to have a better backing store, at which point we're a bit outside of the current scope of this library.

I do wind up transposing when I marshal to OpenGL in, say, Glow.Block, but I was going to have to copy there regardless.

[dpwiz]

Matrices stored row-major (vector of rows), but transformations and projections defined in column-major notation and require transposing. This is so confusing...

Rewriting them in row-major will be a major breaking change, but maybe the gains in clarity are worth it.

[ekmett]

It really depends on what order you tend to do your matrix multiplications. e.g. Working with OpenGL vs. Direct3d flips which you'd prefer, left to right vector matrix vs. right to left matrix vector.

No matter what I pick, half the community is upset, so I went with the one I needed at the time.

-Edward

On Fri, Dec 25, 2020 at 12:49 PM Alexander Bondarenko < notifications@github.com> wrote:

Matrices stored row-major (vector of rows), but transformations and projections defined in column-major notation and require transposing. This is so confusing...

Rewriting them in row-major will be a major breaking change, but maybe the gains in clarity are worth it.

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[dpwiz]

Oh.. That kinda makes sense. M44 stated as row-major, so you'd have to transpose and the transformations are written to be transposed :exploding_head: