Positioning same-ranked nodes in a graph

Question

The following is my graphviz code, and the produced image:

digraph D{
    rankdir = TB
    node[ 
        shape = rect
        style = filled;
        fillcolor = "#C0C0C033"
        fontname = "Roboto"
        width = 5
    ]
    
    A[ label = "Formalize Problem Into Optimization Model" ]
    B[ label = "Is it Possbile To Find A Solving Algo ?" ]
    C[ label = "Is The Problem NP-Hard ?" ]
    D[ label = "Is It Solvable Using Approximation Algo ?" ]
    E[ label = "Is the Problem Inapproximable ?" ]
    
    Done1, Done2[ 
        label = "Done"
        width = 1
        fillcolor = "#44663355"
    ]
    
    Reform[
        label = "Reformulate The Problem"
        width = 3;
    ]
    
    // Invis nodes to simulate ortho-like edges
    invisA2, invisB1, invisC1, invisD1, invisE1[
        shape = point;
        width = 0;
    ]
    
    edge[ 
        style = default;
        fontname = "Roboto"
        weight = 100;
    ]
    
    A -> B 
    B -> C
    C -> D
    D -> E
    
    edge[
        constraint = false;
    ]
    
    // Should Be at the Left Side
    C -> invisC1
    invisC1 -> invisB1
    invisB1 -> B
    B -> Done1
    
    E -> invisE1
    invisE1 -> invisD1
    invisD1 -> D
    D -> Done2
    
    // Should be at the right side (Working Correctly)
    Reform -> invisA2
    invisA2 -> A [label = "                                         "]
    
    {rank = same; invisB1, B, Done1}
    {rank = same; invisC1, C}
    {rank = same; invisD1, D, Done2}
    {rank = same; invisE1, E, Reform}
}

As you can see, the points appears to be between the Done nodes and the main (A, B, C, D, E) nodes; also for no reason they seems to be jiggly.

Since I am going to add labels to the edges, couldn't be using splines = ortho. Is there any ways to make them (To be specific, invisB1, invisC1, invisD1 and invisE1) appear at the left, also keeping all edges straight?

Answer 1

Several smallish tweaks, some just for aesthetics:

• dir=none - aesthetics
• dir=back and reversed edge direction - help position invis nodes on the left
• group=X - help vertical alignment
• turned constraints back to true
• splines=false straight line edges

digraph D{
    rankdir = TB
    splines=false // straight-lines

    node[ 
        shape = rect
        style = filled;
        fillcolor = "#C0C0C033"
        fontname = "Roboto"
        width = 5
    ]
    { node [group=E]  // force/encourage vertical alignment
    A[ label = "Formalize Problem Into Optimization Model" ]
    B[ label = "Is it Possbile To Find A Solving Algo ?" ]
    C[ label = "Is The Problem NP-Hard ?" ]
    D[ label = "Is It Solvable Using Approximation Algo ?" ]
    E[ label = "Is the Problem Inapproximable ?" ]
    }
    
    Done1, Done2[ 
        label = "Done"
        width = 1
        fillcolor = "#44663355"
    ]
    
    Reform[
        label = "Reformulate The Problem"
        width = 3;
        group= B
    ]
    
    // Invis nodes to simulate ortho-like edges
    invisB1, invisC1, invisD1, invisE1[
        shape = point;
        width = 0;
    ]
    invisA2 [ group=B
        shape = point;
        width = 0;
    ]

    edge[ 
        style = solid  //default;
        fontname = "Roboto"
        weight = 100;
    ]
    
    A -> B 
    B -> C
    C -> D
    D -> E

//    we need constraints to be in effect, to influance positioning
//      the constraint documentation may not be complete as to the effect
//    edge[
//        constraint = false;
//    ]
    
    // Should Be at the Left Side
    //C -> invisC1
    invisC1 -> C   [dir=none]
    invisC1 -> invisB1 [dir=none]
    invisB1 -> B
    B -> Done1
    
    //E -> invisE1
    invisE1 -> E   [dir=none]
    invisE1 -> invisD1   [dir=none]
    invisD1 -> D
    D -> Done2

    E -> Reform
    // Should be at the right side (Working Correctly)
    Reform -> invisA2 [dir=none]
    //invisA2 -> A [label = "                                         "]
    A -> invisA2  [dir=back label = "                             "]

    {rank=same   A invisA2}
    {rank = same; invisB1, B, Done1}
    {rank = same; invisC1, C}
    {rank = same; invisD1, D, Done2}
    {rank = same; invisE1, E, Reform}
}

Giving: