Twice-universal coding
It is proved that there exists the twice-universal code W. This means that redundancy of W converges to zero assuming unknown statistical characteristics and unknown memory of source. This code has the following features: 1) for each \(\Omega_ i\), the redundancy of W converges asymptotically to the redundancy of the optimum code on \(\Omega_ i\), 2) if there exists a strongly universal code on a set \(\Omega \subset \Omega_{\infty}\), W will be a strongly universal code, 3) W is weakly universal on \(\Omega_{\infty}\), where \(\Omega_ i\) is a finite set of sources, whereas \(\Omega_{\infty}\) is the set of all sources.
scientific article; zbMATH DE number 3902546