SWMM5 toposort.c Summary

 The toposort.c file in SWMM 5 is responsible for topologically sorting the conveyance network links to ensure proper routing of water flow in the drainage system. It utilizes topological sorting techniques to arrange nodes and links such that all the downstream nodes appear after their respective upstream nodes in the sorted order. This is important for accurate simulation of water flow and for detecting any loops in the network.

Key Components of toposort.c:

1. Adjacency List Creation:

   • createAdjList(): Creates an adjacency list for the nodes, listing the outgoing links for each node. This adjacency list helps identify the direction of flow in the network.
   • adjustAdjList(): Adjusts the adjacency list to handle special cases like DIVIDER nodes. For instance, links that involve diversions are re-ordered in the adjacency list.

2. Topological Sorting:

   • topoSort(): This function performs the topological sort of the drainage network's links. It processes nodes and links in such a way that all links are ordered from upstream to downstream, ensuring that no link leads to a cyclic dependency.
   • toposort_sortLinks(): This function calls createAdjList() to create an adjacency list, then sorts the links using topological sorting methods.

3. Cycle Detection:

   • findCycles(): This function checks for loops or cycles in the network, where flow might get trapped in a cycle and prevent proper simulation. It uses the spanning tree of the network to identify such cycles and handle them accordingly.
   • findSpanningTree(): This function finds a spanning tree starting from a node and traces through the network, identifying and marking links as part of the spanning tree.
   • evalLoop(): This function evaluates whether a set of links forms a cycle or not. If a cycle is detected, it is reported.

4. Cycle Detection in Dummy Links:

   • checkDummyLinks(): This function checks for nodes that have both incoming and outgoing dummy links. Dummy links are placeholders for certain types of flow, and having both incoming and outgoing dummy links could lead to ambiguous sorting.

Purpose of toposort.c:

• Topological Sorting: Ensures that the nodes and links are processed in the correct order during simulation. It is critical that upstream nodes and their links are processed before downstream nodes to simulate accurate water flow.

• Cycle Detection: Prevents the simulation from proceeding if there are any loops in the system, as loops in the flow network would result in incorrect calculations.

• Handling Special Nodes: Specifically handles DIVIDER nodes and dummy links to make sure the routing works correctly even in complex networks with special conditions.

Overall, toposort.c is crucial for setting up the routing of water flow in the SWMM simulation, ensuring that all nodes and links are ordered correctly for accurate simulation results.