Dependency graph

21-eulerian/README.md

@@ -8,7 +8,7 @@ This unit covers Eulerian paths and associated subjects:
 ## Prerequisites
 - Unit 1: [Complexity](../01-complexity)
 - Unit 6: [Graph basics](../06-graph-basics)
-- Unit 14: [Graph traversal](../14-graph-traversal)
+- Unit 14: [Graph traversal](../14-traversal)
 
 ## Practice problems
 

README.md

@@ -40,3 +40,5 @@ Here is the list of completed and planned teaching units. As they are still unde
 30. Problem decomposition
 31. Advanced graph problems (2-SAT, MWIS (tree, bipartite))
 32. Sparse table, lowest common ancestor
+
+![Dependency graph for the units](dependency_graph.png)

scripts/dependency_graph.py

@@ -0,0 +1,138 @@
+#!/usr/bin/env python3
+import sys, os, re, collections, shutil, subprocess
+
+BASEDIR = os.path.abspath(os.path.join(os.path.dirname(__file__), os.path.pardir))
+
+Unit = collections.namedtuple("Unit", ["idx", "name", "dir"])
+
+def get_units():
+    def make_unit(tpl):
+        return Unit(int(tpl[0]), *tpl[1:])
+
+    unit_re = r"(\d+). \[(.+)]\(([^)]+)\)"
+    with open(os.path.join(BASEDIR, "README.md")) as f:
+        main_readme = f.read()
+    return dict((tpl[2], make_unit(tpl)) for tpl in re.findall(unit_re, main_readme))
+
+
+def get_dependencies(unit, units):
+    dep_re = r"\[.*\]\(\.\./([^)]*)\)"
+    try:
+        with open(os.path.join(BASEDIR, unit.dir, "README.md")) as f:
+            readme_content = f.read()
+    except IOError:
+        sys.stderr.write("Cannot find README file for '%s'\n" % unit.name)
+        return []
+    deps = [] 
+    used = set()
+    for dep in re.findall(dep_re, readme_content):
+        if dep not in units:
+            sys.stderr.write("Unknown dependency: %s\n" % dep)
+            continue
+        if units[dep].idx not in used:
+            deps.append(units[dep])
+            used.add(units[dep].idx)
+    return deps
+
+
+def all_deps(deps, unit):
+    if unit.idx in all_deps.cache:
+        return all_deps.cache[unit.idx]
+    s = set()
+    for d in deps[unit]:
+        s |= all_deps(deps, d)
+        s.add(d)
+    return all_deps.cache.setdefault(unit.idx, s)
+all_deps.cache = {}
+
+def eliminate_transitive_deps(dep_dict):
+    for unit, deps in dep_dict.items():
+        transitive = set()
+        for d in deps:
+            transitive |= all_deps(dep_dict, d)
+        for t in transitive:
+            if t in deps:
+                deps.remove(t)
+
+def summarize_single(u):
+    return "%02d-%s" % (u.idx, "".join(t[0].upper() for t in u.dir.split("-") if t and t.isalpha()))
+
+def summarize(units):
+    return dict((summarize_single(u), u) for u in units.values())
+
+def build_dot(dependencies):
+    edges = [(summarize_single(u), summarize_single(v)) for u in sorted(dependencies) for v in sorted(dependencies[u])]
+    dot_edges = "\n".join('"%s" -> "%s"' % e for e in edges)
+    return "digraph {\n%s\n}" % dot_edges
+
+def add_links(svg, summarized):
+    def replace(tpl):
+        total, title = tpl.groups()
+        title = title.replace("-", "-")
+        return "<a xlink:href=\"%s\">%s</a>" % (summarized[title].dir, total)
+
+    node_regex = r'(<g[^>]*>\s*<title>([^<]*)</title>\s*<ellipse[^/]*/>\s*<text[^>]*>[^<]*</text>\s*</g>)'
+    return re.sub(node_regex, replace, svg)
+
+def toposort(G, node=None, vis=None):
+    if vis is None:
+        vis = set()
+
+    if node is None:
+        res = []
+        for node in sorted(G, key=lambda n: n.idx):
+            res += toposort(G, node, vis)
+        return res
+    else:
+        if node in vis: return []
+        vis.add(node)
+
+        res = []
+        for neigh in sorted(G[node], key=lambda n: n.idx):
+            res += toposort(G, neigh, vis)
+        res.append(node)
+        return res
+
+if __name__ == "__main__":
+    # Find the graphviz dot executable
+    dot_location = shutil.which("dot")
+    if not dot_location:
+        sys.stderr.write("Cannot find the 'dot' executable, please install graphviz\n")
+        sys.exit(1)
+
+    # Parse main readme
+    units = get_units()
+
+    # Build the dependency_graph, parsing unit readme's
+    dependencies = dict((u, get_dependencies(u, units)) for _, u in units.items())
+
+    # Eliminate dependencies of the form a->c where a->b and b->c
+    eliminate_transitive_deps(dependencies)
+
+    # A graphviz representation
+    dot_graph = build_dot(dependencies)
+
+    # Make the svg
+    pipe = subprocess.Popen([dot_location, "-Tsvg"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+    (svg, _) = pipe.communicate(bytes(dot_graph, "utf-8"))
+
+    # Add hyperlinks to the units in the svg
+    # Doesn't seem to work in github unfortunately (maybe with gh-pages)
+    svg = add_links(str(svg, "utf-8"), summarize(units))
+
+    # Write the svg
+    with open(os.path.join(BASEDIR, "dependency_graph.svg"), "w") as out:
+        out.write(svg)
+
+    # Svg is not displayed in the readme on the repo, so we use a png
+    pipe = subprocess.Popen([dot_location, "-Tpng"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+    (png, _) = pipe.communicate(bytes(dot_graph, "utf-8"))
+    with open(os.path.join(BASEDIR, "dependency_graph.png"), "wb") as out:
+        out.write(png)
+
+    # Some toposorting
+    # We might want something else for the reporting
+    print()
+    print("Recommended order:")
+    for unit in toposort(dependencies):
+        print(" ", "Unit %s:" % unit.idx, unit.name)