Stretchwidth
Stretchwidth is a layering algorithm proposed by Nikolas S. Nikolov, Alexandre Tarassov, and Jürgen Branke
in "In Search for Efficient Heuristics for Minimum-Width Graph Layering with Consideration of Dummy Nodes"
The description of this algorithm in this page refers to a top-down graph and so it may differ from the description of other algorithm in KLay Layered.
The algorithm tries to minimize the width of the layered graph by trying to apply a boundary in every layer and increasing this boundary, if it fails (e.g. if it would create an empty layer).
This approach first orders the nodes by their rank. Whereby the rank of a node v is defined as the maximum of the incoming edges in v and the maximum of the outgoing edges of all predecessors. Then it starts by the bottom of the graph and places the layerless node with the highest rank, whose successors are all already placed in a layer below.
If the placement of a node would violate the boundary, the algorithm starts with the next layer.
Precondition: the graph has no cycles, but might contain self-loops
Postcondition: all nodes have been assigned a layer such that edges connect only nodes from layers with increasing indices