NETWORK/ GRAPH LAYOUT

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Author :Bhekimpilo Ndhlela

Name of Project :Network/ Graph Layout

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Graphical User Interface Example:

Text File Format

 0 -> 1

 1 -> 2

 2 -> 3

 3 -> 4

 7 -> 1

 1 -> 5

 3 -> 6

 2 -> 8

 2 -> 8

 1 -> 9

 10 -> 1

 10 -> 1

 10 -> 1

 10 -> 1

 8 -> 6

 8 -> 6

 8 -> 6


 NOTE: Some of the edges are repeated because i wanted to illustrate the coloring of the edges that occur the most.
 This is specified or briefly explained at the "What Happens:" Section, the last paragraph.

Output Image of the Above Graph:

Note: Cyclic Graphs

   Please note that cyclic graphs or networks are not used in this algorithm, The algorithm works for uncyclic graphs or networks. If a cycle is
   detected in the graph at hand then the program or application will terminate and indicate that a cycle has been detected.

Dependancies :

Graph/ Network Layout depends on classes written by me(Bhekimpilo Ndhlela) which include:

   Layout.java (main/client library)

   GraphDummyNode.java

   GraphInitializer.java

   GraphNodeOrdering.java

   GraphOutput.java

   GraphRanking.java
   
   LayoutUnitTester.java(for coverage testing purposes)

It also depends on the sorting algorithms libraries from Princeton University, I rewrote some of them and edited most of them these algorithms include:

   Merge.java(inplace sorting algorithm for the BaryCenter method)

   AcyclicLP.java

   Bag.java

   DepthFirstOrder.java

   Digraph.java

   DirectedCycle.java

   DirectedEdge.java

   Queue.java
   
   Stack.java

   StdDraw.java

   Topological.java

How and What To Compile:

Compilation : javac Layout.java

Ignore The Following notes and execute.

 Note: Some input files use unchecked or unsafe operations.

 Note: Recompile with -Xlint:unchecked for details.

Execution: java Layout "Path of your desired graph"

 For Example: java ImageSort ~/LocalRepo/testCases/SpecGraph.txt

What Happens(Briefly):

 The Algorithm has four major components. After having read the input file and creating the nodes and edges, it first ranks the nodes into different
 levels (Smin, Smax, S0, S1, ..., Sk). Secondly, it adds dummy nodes to the graph where edges stretch over rank sets. Thirdly, it orders the nodes 
 inside each level to minimize edge crossings. The last step is to find coordinate positions for each node and spline control points to draw all the
 edges between the nodes.

 Consider each rank set Si. For every node v in Si, consider its adjacent nodes w (in other ranked sets). If v is more than one rank away from any w,
 create a virtual (dummy) node t in rank set Si+1, and add a chain of virtual edges and nodes v-t0, t0-t1,..., tk-w, stepping through rank sets that
 are one rank apart.

 Draw the edges as straight lines, with bends at the virtual nodes. Do not draw the virtual nodes. Finally, edges are to be colourcoded to indicate 
 that they occur often (or not, if they occur only a few times). That is, you have to keep count of how often every edge occurs in the graph, and then
 colour the edges that occur the most red, the edges that occur second-most orange, and the edges that occur third-most dark yellow (make sure that the
 yellow is dark enough to be clearly visible on the screen). All other edges are to be drawn in black. For example, suppose there are five parallel
 edges between nodes 1 and 2, four edges between nodes 2 and 3, three edges between 1 and 3, and all other edges occur only once. Then you have to draw
 a single edge between 1 and 2, but colour it red, one edge coloured orange between 2 and 3, and one edge coloured dark yellow between 1 and 3. All other
 edges will be black.