DAGVIZ examples

Simple DAG

This example is taken from D3-DAG's example section. We start by importing DAGVIZ and constructing the DAG object. The DAG object is a simple wrapper around networkx's DiGraph.

import dagviz
import networkx as nx

g = nx.DiGraph()

Next we start adding nodes and edges.

for i in range(21):
    g.add_node(f"n{i}")

g.add_edge("n1", "n14")
g.add_edge("n8", "n14")
g.add_edge("n8", "n0")
g.add_edge("n0", "n16")
g.add_edge("n16", "n10")
g.add_edge("n21", "n10")
g.add_edge("n21", "n12")
g.add_edge("n21", "n7")
g.add_edge("n12", "n4")
g.add_edge("n12", "n13")
g.add_edge("n4", "n9")
g.add_edge("n4", "n13")
g.add_edge("n13", "n20")
g.add_edge("n9", "n18")
g.add_edge("n9", "n6")
g.add_edge("n18", "n5")
g.add_edge("n15", "n6")
g.add_edge("n19", "n17")
g.add_edge("n17", "n6")
g.add_edge("n17", "n7")
g.add_edge("n2", "n11")
g.add_edge("n11", "n3")
g.add_edge("n3", "n7")

Rendering the graph is as simple as you would expect it to be in Jupyter.

dagviz.Metro(g)

Linux kernel commit history

Let's try something a bit more challenging: the last thousand commits of the Linux kernel git repository (dated June 20th, 2021). I generated a git log for the linux kernel using

git log --oneline --parents > linux-git-log.txt

This gives a long list of lines like:

cba5e97280f5 9df7f15ee922 a7b359fc6a37 Merge tag 'sched_urgent_for_v5.13_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Where the first token is this commit hash, the subsequent hashes are parents, and the text is the summary.

The script below parses this log and turns it into a networkx graph:

H = nx.DiGraph()
hashlen = None
with open("../linux-git-log.txt", "rt") as fs:
    for i, l in enumerate(fs):
        if i==1000:
            break
        tokens = l.rstrip().split(" ")
        if hashlen is None:
            hashlen = len(tokens[0])
        commits = []
        for j, t in enumerate(tokens):
            if len(t)!=hashlen:
                break;
            try:
                commits.append(int(t,16))
            except ValueError:
                break
        H.add_node(commits[0], label=" ".join(tokens[j:]))
        for p in commits[1:]:
            H.add_edge(commits[0], p)
        

Again, rendering the graph is simple:

dagviz.Metro(H)