// The matrix is created on demand the first time it is requested, then cached. There are two
// reasons for this:
// 1. This work will never be done if the caller only installs 1D Reader objects, or if a
// The matrix is created on demand the first time it is requested, then cached. There are two
// reasons for this:
// 1. This work will never be done if the caller only installs 1D Reader objects, or if a