Expand description
Generic runtime-dispatch transposed sub-matrix GEMV (y += Aᵀ · x, row
stride lda).
Generalizes super::gemv_transpose() to a row-major sub-matrix:
nrows × ncols with leading dimension lda ≥ ncols. lda = ncols recovers
the packed transpose. Computes Σᵢ xᵢ·A[i,:] (sum of the strided rows scaled
by x), vectorizing across the ncols output lanes with no horizontal
reduction. Admits the Aᵀ·x reduction over a trailing/leading block of a
larger buffer — e.g. forming Aw = Σⱼ wⱼ·colⱼ in a reflector apply — without
copying it out. Accumulates into y.