TopologicalOrder

Which topological order ModelGraph.topological_order returns. Every kind lists each node once, after every node whose output it reads; the kinds differ in how they order the nodes that could go either way. Deterministic: ties go to the node whose name sorts first, the order nodes() lists. Structural: read off the structure alone, from the graph outputs in output order back through each node's inputs in input-port order, so renaming nodes never changes it; the nodes no graph output depends on come last, in the Deterministic order. MinMemory: an order that keeps fewer bytes alive at its peak, counting each value as freed after its last reader, the lowest peak a bounded search over valid orders finds; the Deterministic order when the search finds none lower or declines the graph.