21.4.3 Euler Backward

Euler backward steps are comprised of two half steps. The first is identical to a forward step and the second fills $\tau$ variables within the memory window with $\tau+1$ data from the first step. When the memory window is opened all the way, an euler shuffle is required to get data properly aligned in preparation for the next time step. This is the only data movement required when the memory window is fully opened^21.5.