Similarly, template class RTM3D provides the implementation of time step iteration in 3D-RTM. In this class, function forward emulates a single time step in the forward propagation path. There are multiple overload of this function for various boundary conditions e.g. Random Boudnayr Condition (RBC).
The block diagram of forward function given in Figure 1 shows the achieved temporal parallelims, namely computing the wavefield at time step \(t\) and \(t+1\) simultaneouly. The streaming interfaces of the basic modules allow them to be connected directly by FIFOs, which hold the wavefield data without storing them back to external memory. This streamlined architecture is the key to achieve high parallelism both spatially and temporally. Each Forward streaming module labeled with F basically takes the wavefield data from the last time stamp then computes the wavefield for current time stamp and outputs both the data and boundary data to other modules in streams.
| [1] | E.Dussaud,W.W.Symes,P.Williamson,L.Lemaistre,P.Singer, B. Denel, and A. Cherrett, “Computational strategies for reversetime migration,” in SEG Technical Program Expanded Abstracts 2008. Society of Exploration Geophysicists, 2008, pp. 2267– 2271. |
| [2] |
|