FastFlow: GPU Acceleration of Flow and Depression Routing for Landscape Simulation

Input : Terrain cells $\backslash mathcal\{T\}$, set of depression basins $\backslash mathcal\{D\}$
Output: Updated recipients

1 if Depression jumping variant then
2   foreach depression $d\; \backslash in\; \backslash mathcal\{D\}$ in parallel do
3     $l\; \backslash leftarrow$ local minimum of $d$
4     recipient of $l\; \backslash leftarrow$ outlet of $d$
5   end
6 else
7   // Depression Carving Variant
8   tag $\backslash leftarrow$ False for all cells
9   foreach depression $d\; \backslash in\; \backslash mathcal\{D\}$ in parallel do
10    tag[saddle of $d$] $\backslash leftarrow$ True
11    end
12    // recipient is local to next two loops
13    for $i\; \backslash leftarrow\; 1$ to $\backslash log\_2(|\backslash mathcal\{T\}|)$ do
14      foreach cell $c\; \backslash in\; \backslash mathcal\{T\}$ in parallel do
15        if tag[$c$] then
16          tag[recipient of $c$] $\backslash leftarrow$ True
17          recipient of $c\; \backslash leftarrow$ recipient of recipient of $c$
18        end
19      end
20      foreach cell $c\; \backslash in\; \backslash mathcal\{T\}$ in parallel do
21        if tag[recipient of $c$] and $c$ is not a local minimum
22        then
23          recipient of recipient of $c\; \backslash leftarrow\; c$
24        end
25      end
26    end
27    foreach depression $d\; \backslash in\; \backslash mathcal\{D\}$ in parallel do
28      recipient of saddle of $d\; \backslash leftarrow$ outlet of $d$
29    end