3 ms·
> 9. Transposing a matrix (Like the inverse A^{-1}, the explicit transpose A^t is often not needed) Most matrix libraries should make transpose, conjugate, and
by jcranmer 4y ago
> 9. Transposing a matrix (Like the inverse A^{-1}, the explicit transpose A^t is often not needed)
Most matrix libraries should make transpose, conjugate, and conjugate transpose just twiddling a bit on its internal representation--BLAS routines should have a parameter on them saying if the input matrix needs to be transposed and/or conjugated before doing an operation.
- joppy 4y agoDoesn’t memory layout still matter? Assumedly matrix-vector products like Av are fastest if the rows of A are contiguous in memory, and vector-matrix products vA are fastest when the columns are contiguous in memory. So sometimes one would really want to actually transpose the matrix, rather than reinterpreting the indexing scheme.