Projected gradient for multidimensional array

[rkruegs123]

Hi -- I have an array that is mxnxn. Each of the m nxn matrices represents a single "frame." I wish to enforce that each nxn matrix/frame is a doubly-stochastic matrix. For a single nxn matrix, I could use projected gradients with the birkhoff projection. However, I would like to apply this constraint to every nxn matrix.

Does anyone know how to best implement this?