Topological sort/Extracted top item: Difference between revisions

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Compile order for ip1: [extra1, ipcommon, ip1a, ip1]
Compile order for ip1: [extra1, ipcommon, ip1a, ip1]
</pre>

=={{header|Perl}}==
<lang perl>#!/usr/bin/perl

use strict;
use warnings;
use List::Util qw( uniq );

my $deps = <<END;
top1 des1 ip1 ip2
top2 des1 ip2 ip3
ip1 extra1 ip1a ipcommon
ip2 ip2a ip2b ip2c ipcommon
des1 des1a des1b des1c
des1a des1a1 des1a2
des1c des1c1 extra1
END

sub before
{
map { $deps =~ /^$_\b(.+)/m ? before( split ' ', $1 ) : (), $_ } @_
}

1 while $deps =~ s/^(\w+)\b.*?\K\h+\1\b//gm; # remove self dependencies
print "TOP LEVELS: @{[grep $deps !~ /\h$_\b/, $deps =~ /^\w+/gm]}\n";
print "\nTARGET $_ ORDER: @{[ uniq before split ]}\n"
for $deps =~ /^\w+/gm, 'top1 top2';</lang>
{{out}}
<pre>
TOP LEVELS: top1 top2

TARGET top1 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1

TARGET top2 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip2a ip2b ip2c ipcommon ip2 ip3 top2

TARGET ip1 ORDER: extra1 ip1a ipcommon ip1

TARGET ip2 ORDER: ip2a ip2b ip2c ipcommon ip2

TARGET des1 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1

TARGET des1a ORDER: des1a1 des1a2 des1a

TARGET des1c ORDER: des1c1 extra1 des1c

TARGET top1 top2 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1 ip3 top2
</pre>
</pre>


Line 619: Line 666:
top1 top2
top1 top2
</pre>
</pre>

=={{header|Phix}}==
=={{header|Phix}}==
Minor tweaks to the Topological_sort code: top_levels, propagate() and -1 now means "not required".
Minor tweaks to the Topological_sort code: top_levels, propagate() and -1 now means "not required".

Revision as of 17:12, 17 January 2019

Topological sort/Extracted top item is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Given a mapping between items, and items they depend on, a topological sort orders items so that no item precedes an item it depends upon.

The compiling of a design in the VHDL language has the constraint that a file must be compiled after any file containing definitions it depends on. A tool exists that extracts file dependencies.

  • Assume the file names are single words, given without their file extensions.
  • Files mentioned as only dependants, have no dependants of their own, but their order of compiling must be given.
  • Any self dependencies should be ignored.


A top level file is defined as a file that:

  1. Has dependents.
  2. Is not itself the dependent of another file


Task Description

Given the following file dependencies as an example:

FILE    FILE DEPENDENCIES
====    =================
top1    des1 ip1 ip2
top2    des1 ip2 ip3
ip1     extra1 ip1a ipcommon
ip2     ip2a ip2b ip2c ipcommon
des1    des1a des1b des1c
des1a   des1a1 des1a2
des1c   des1c1 extra1

The task is to create a program that given a graph of the dependency:

  1. Determines the top levels from the dependencies and show them.
  2. Extracts a compile order of files to compile any given (usually top level) file.
  3. Give a compile order for file top1.
  4. Give a compile order for file top2.

You may show how to compile multiple top levels as a stretch goal

Note: this task differs from task Topological sort in that the order for compiling any file might not include all files; and that checks for dependency cycles are not mandated.

Related task



C

Take code from Topological sort#c and add/change the following: <lang c>char input[] = "top1 des1 ip1 ip2\n" "top2 des1 ip2 ip3\n" "ip1 extra1 ip1a ipcommon\n" "ip2 ip2a ip2b ip2c ipcommon\n" "des1 des1a des1b des1c\n" "des1a des1a1 des1a2\n" "des1c des1c1 extra1\n";

... int find_name(item base, int len, const char *name) { int i; for (i = 0; i < len; i++) if (!strcmp(base[i].name, name)) return i; return -1; }

int depends_on(item base, int n1, int n2) { int i; if (n1 == n2) return 1; for (i = 0; i < base[n1].n_deps; i++) if (depends_on(base, base[n1].deps[i], n2)) return 1; return 0; }

void compile_order(item base, int n_items, int *top, int n_top) { int i, j, lvl; int d = 0; printf("Compile order for:"); for (i = 0; i < n_top; i++) { printf(" %s", base[top[i]].name); if (base[top[i]].depth > d) d = base[top[i]].depth; } printf("\n");

for (lvl = 1; lvl <= d; lvl ++) { printf("level %d:", lvl); for (i = 0; i < n_items; i++) { if (base[i].depth != lvl) continue; for (j = 0; j < n_top; j++) { if (depends_on(base, top[j], i)) { printf(" %s", base[i].name); break; } } } printf("\n"); } printf("\n"); }

int main() { int i, n, bad = -1; item items; n = parse_input(&items);

for (i = 0; i < n; i++) if (!items[i].depth && get_depth(items, i, bad) < 0) bad--;

int top[3]; top[0] = find_name(items, n, "top1"); top[1] = find_name(items, n, "top2"); top[2] = find_name(items, n, "ip1");

compile_order(items, n, top, 1); compile_order(items, n, top + 1, 1); compile_order(items, n, top, 2); compile_order(items, n, top + 2, 1);

return 0; }</lang>output (the last item is just to show that it doesn't have to be top level)<lang>Compile order for: top1 level 1: extra1 ip1a ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 level 2: ip1 ip2 des1a des1c level 3: des1 level 4: top1

Compile order for: top2 level 1: ip3 extra1 ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 level 2: ip2 des1a des1c level 3: des1 level 4: top2

Compile order for: top1 top2 level 1: ip3 extra1 ip1a ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 level 2: ip1 ip2 des1a des1c level 3: des1 level 4: top1 top2

Compile order for: ip1 level 1: extra1 ip1a ipcommon level 2: ip1</lang>

Go

<lang go>package main

import (

   "fmt"
   "strings"

)

var data = ` FILE FILE DEPENDENCIES

=============

top1 des1 ip1 ip2 top2 des1 ip2 ip3 ip1 extra1 ip1a ipcommon ip2 ip2a ip2b ip2c ipcommon des1 des1a des1b des1c des1a des1a1 des1a2 des1c des1c1 extra1`

func main() {

   g, dep, err := parseLibDep(data)
   if err != nil {
       fmt.Println(err)
       return
   }
   // Task 1: Determine top levels.  The input parser returns a list (dep)
   // of libraries that are dependants of at least one other library.
   // Top levels are then libraries in the graph that are not on this list.
   var tops []string
   for n := range g {
       if !dep[n] {
           tops = append(tops, n)
       }
   }
   fmt.Println("Top levels:", tops)
   // Task 2 is orderFrom method, below
   showOrder(g, "top1")         // Task 3
   showOrder(g, "top2")         // Task 4
   showOrder(g, "top1", "top2") // Stretch
   fmt.Println("Cycle examples:")
   // reparse with a cyclic dependency
   g, _, err = parseLibDep(data + `

des1a1 des1`)

   if err != nil {
       fmt.Println(err)
       return
   }
   showOrder(g, "top1")       // runs into cycle
   showOrder(g, "ip1", "ip2") // does not involve cycle

}

func showOrder(g graph, target ...string) {

   order, cyclic := g.orderFrom(target...)
   if cyclic == nil {
       reverse(order) // compile order is reverse of dependency order
       fmt.Println("Target", target, "order:", order)
   } else {
       fmt.Println("Target", target, "cyclic dependencies:", cyclic)
   }

}

func reverse(s []string) {

   last := len(s) - 1
   for i, e := range s[:len(s)/2] {
       s[i], s[last-i] = s[last-i], e
   }

}

type graph map[string][]string // adjacency list representation type depList map[string]bool

// parseLibDep parses the text format of the task and returns a dependency // graph and a list of nodes that are dependants of at least one other node. func parseLibDep(data string) (g graph, d depList, err error) {

   lines := strings.Split(data, "\n")
   if len(lines) < 3 || !strings.HasPrefix(lines[2], "=") {
       return nil, nil, fmt.Errorf("data format")
   }
   lines = lines[3:]
   g = graph{}
   d = depList{}
   for _, line := range lines {
       libs := strings.Fields(line)
       if len(libs) == 0 {
           continue
       }
       lib := libs[0]
       var deps []string
       for _, dep := range libs[1:] {
           g[dep] = g[dep]
           if dep == lib {
               continue
           }
           for i := 0; ; i++ {
               if i == len(deps) {
                   deps = append(deps, dep)
                   d[dep] = true
                   break
               }
               if dep == deps[i] {
                   break
               }
           }
       }
       g[lib] = deps
   }
   return g, d, nil

}

// OrderFrom produces a topological ordering of the subgraph of g reachable // from a set of start nodes, where the subgraph is a directed acyclic graph. // If the subgraph contains a cycle, orderFrom returns the first cycle found // and returns a nil order. Cycles which are in the graph but not in the // subgraph reachable from start are not detected. func (g graph) orderFrom(start ...string) (order, cyclic []string) {

   L := make([]string, len(g))
   i := len(L)
   temp := map[string]bool{}
   perm := map[string]bool{}
   var cycleFound bool
   var cycleStart string
   var visit func(string)
   visit = func(n string) {
       switch {
       case temp[n]:
           cycleFound = true
           cycleStart = n
           return
       case perm[n]:
           return
       }
       temp[n] = true
       for _, m := range g[n] {
           visit(m)
           if cycleFound {
               if cycleStart > "" {
                   cyclic = append(cyclic, n)
                   if n == cycleStart {
                       cycleStart = ""
                   }
               }
               return
           }
       }
       delete(temp, n)
       perm[n] = true
       i--
       L[i] = n
   }
   for _, n := range start {
       if perm[n] {
           continue
       }
       visit(n)
       if cycleFound {
           return nil, cyclic
       }
   }
   return L[i:], nil

}</lang>

Output:
Top levels: [top1 top2]
Target [top1] order: [des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1]
Target [top2] order: [des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip2a ip2b ip2c ipcommon ip2 ip3 top2]
Target [top1 top2] order: [des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1 ip3 top2]
Cycle examples:
Target [top1] cyclic dependencies: [des1a1 des1a des1]
Target [ip1 ip2] order: [extra1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2]

J

Derived from the topological sort implementation:

<lang j>compileOrder=: dyad define

 targets=. ;: x
 parsed=. <@;:;._2 y
 names=. ~.({.&>parsed),targets,;parsed
 depends=. (> =@i.@#) names e.S:1 (#names){.parsed
 depends=. (+. +./ .*.~)^:_ depends
 b=. +./depends (] , #~) names e. targets
 names (</.~ \: ~.@])&(keep&#) +/"1 depends
 (b#names) (</.~ /: ~.@]) +/ }.+./ .*.~&(b#"1 b#depends)^:a: 1

)

topLevel=: [: ({.&> -. [:;}.&.>) <@;:;._2 </lang>

The changes include:

  1. Added an argument for the target(s) we wish to find dependencies for
  2. Make sure that these targets are included in our dependency structures
  3. Make sure that things we can depend on are included in our dependency structures
  4. Select these targets, and the things they depend on, once we know what depends on what
  5. When ordering names by dependencies:
    1. only consider names and dependencies we want to keep
    2. extract names grouped by their dependency chain length

Example:

<lang j>dependencies=: noun define

 top1    des1 ip1 ip2
 top2    des1 ip2 ip3
 ip1     extra1 ip1a ipcommon
 ip2     ip2a ip2b ip2c ipcommon
 des1    des1a des1b des1c
 des1a   des1a1 des1a2
 des1c   des1c1 extra1

)

  >topLevel dependencies

top1 top2

  ;:inv@> 'top1' compileOrder dependencies

extra1 ip1a ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 ip1 ip2 des1a des1c des1 top1

  ;:inv@> 'top2' compileOrder dependencies

ip3 extra1 ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 ip2 des1a des1c des1 top2

  ;:inv@> 'top1 top2' compileOrder dependencies

ip3 extra1 ip1a ipcommon ip2a ip2b ip2c des1b des1a1 des1a2 des1c1 ip1 ip2 des1a des1c des1 top1 top2 </lang>

Java

Works with: Java version 8

<lang java>import java.util.*; import static java.util.Arrays.asList; import static java.util.stream.Collectors.toList;

public class TopologicalSort2 {

   public static void main(String[] args) {
       String s = "top1,top2,ip1,ip2,ip3,ip1a,ip2a,ip2b,ip2c,ipcommon,des1,"
               + "des1a,des1b,des1c,des1a1,des1a2,des1c1,extra1";
       Graph g = new Graph(s, new int[][]{
           {0, 10}, {0, 2}, {0, 3},
           {1, 10}, {1, 3}, {1, 4},
           {2, 17}, {2, 5}, {2, 9},
           {3, 6}, {3, 7}, {3, 8}, {3, 9},
           {10, 11}, {10, 12}, {10, 13},
           {11, 14}, {11, 15},
           {13, 16}, {13, 17},});
       System.out.println("Top levels: " + g.toplevels());
       String[] files = {"top1", "top2", "ip1"};
       for (String f : files)
           System.out.printf("Compile order for %s %s%n", f, g.compileOrder(f));
   }

}

class Graph {

   List<String> vertices;
   boolean[][] adjacency;
   int numVertices;
   public Graph(String s, int[][] edges) {
       vertices = asList(s.split(","));
       numVertices = vertices.size();
       adjacency = new boolean[numVertices][numVertices];
       for (int[] edge : edges)
           adjacency[edge[0]][edge[1]] = true;
   }
   List<String> toplevels() {
       List<String> result = new ArrayList<>();
       // look for empty columns
       outer:
       for (int c = 0; c < numVertices; c++) {
           for (int r = 0; r < numVertices; r++) {
               if (adjacency[r][c])
                   continue outer;
           }
           result.add(vertices.get(c));
       }
       return result;
   }
   List<String> compileOrder(String item) {
       LinkedList<String> result = new LinkedList<>();
       LinkedList<Integer> queue = new LinkedList<>();
       queue.add(vertices.indexOf(item));
       while (!queue.isEmpty()) {
           int r = queue.poll();
           for (int c = 0; c < numVertices; c++) {
               if (adjacency[r][c] && !queue.contains(c)) {
                   queue.add(c);
               }
           }
           result.addFirst(vertices.get(r));
       }
       return result.stream().distinct().collect(toList());
   }

}</lang>

Top levels: [top1, top2]
Compile order for top1 [extra1, des1c1, des1a2, des1a1, des1c, des1b, des1a, ip2c, ip2b, ip2a, ipcommon, ip1a, des1, ip2, ip1, top1]
Compile order for top2 [extra1, des1c1, des1a2, des1a1, des1c, des1b, des1a, ipcommon, ip2c, ip2b, ip2a, des1, ip3, ip2, top2]
Compile order for ip1 [extra1, ipcommon, ip1a, ip1]

Kotlin

Translation of: Java

<lang scala>// version 1.1.51

import java.util.LinkedList

val s = "top1, top2, ip1, ip2, ip3, ip1a, ip2a, ip2b, ip2c, ipcommon, des1, " +

       "des1a, des1b, des1c, des1a1, des1a2, des1c1, extra1"

val deps = mutableListOf(

   0 to 10, 0 to 2, 0 to 3,
   1 to 10, 1 to 3, 1 to 4,
   2 to 17, 2 to 5, 2 to 9,
   3 to 6, 3 to 7, 3 to 8, 3 to 9,
   10 to 11, 10 to 12, 10 to 13,
   11 to 14, 11 to 15,
   13 to 16, 13 to 17

)

val files = listOf("top1", "top2", "ip1")

class Graph(s: String, edges: List<Pair<Int, Int>>) {

   val vertices = s.split(", ")
   val numVertices = vertices.size
   val adjacency = List(numVertices) { BooleanArray(numVertices) }
   init {
       for (edge in edges) adjacency[edge.first][edge.second] = true
   }
   fun topLevels(): List<String> {
       val result = mutableListOf<String>()
       // look for empty columns
       outer@ for (c in 0 until numVertices) {
           for (r in 0 until numVertices) {
               if (adjacency[r][c]) continue@outer
           }
           result.add(vertices[c])
       }
       return result
   }
   fun compileOrder(item: String): List<String> {
       val result = LinkedList<String>()
       val queue  = LinkedList<Int>()
       queue.add(vertices.indexOf(item))
       while (!queue.isEmpty()) {
           val r = queue.poll()
           for (c in 0 until numVertices) {
               if (adjacency[r][c] && !queue.contains(c)) queue.add(c)
           }
           result.addFirst(vertices[r])
       }
       return result.distinct().toList()
   }

}

fun main(args: Array<String>) {

   val g = Graph(s, deps)
   println("Top levels:  ${g.topLevels()}")
   for (f in files) println("\nCompile order for $f: ${g.compileOrder(f)}")

}</lang>

Output:
Top levels:  [top1, top2]

Compile order for top1: [extra1, des1c1, des1a2, des1a1, des1c, des1b, des1a, ip2c, ip2b, ip2a, ipcommon, ip1a, des1, ip2, ip1, top1]

Compile order for top2: [extra1, des1c1, des1a2, des1a1, des1c, des1b, des1a, ipcommon, ip2c, ip2b, ip2a, des1, ip3, ip2, top2]

Compile order for ip1: [extra1, ipcommon, ip1a, ip1]

Perl

<lang perl>#!/usr/bin/perl

use strict; use warnings; use List::Util qw( uniq );

my $deps = <<END; top1 des1 ip1 ip2 top2 des1 ip2 ip3 ip1 extra1 ip1a ipcommon ip2 ip2a ip2b ip2c ipcommon des1 des1a des1b des1c des1a des1a1 des1a2 des1c des1c1 extra1 END

sub before

 {
 map { $deps =~ /^$_\b(.+)/m ? before( split ' ', $1 ) : (), $_ } @_
 }

1 while $deps =~ s/^(\w+)\b.*?\K\h+\1\b//gm; # remove self dependencies print "TOP LEVELS: @{[grep $deps !~ /\h$_\b/, $deps =~ /^\w+/gm]}\n"; print "\nTARGET $_ ORDER: @{[ uniq before split ]}\n"

 for $deps =~ /^\w+/gm, 'top1 top2';</lang>
Output:
TOP LEVELS: top1 top2

TARGET top1 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1

TARGET top2 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip2a ip2b ip2c ipcommon ip2 ip3 top2

TARGET ip1 ORDER: extra1 ip1a ipcommon ip1

TARGET ip2 ORDER: ip2a ip2b ip2c ipcommon ip2

TARGET des1 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1

TARGET des1a ORDER: des1a1 des1a2 des1a

TARGET des1c ORDER: des1c1 extra1 des1c

TARGET top1 top2 ORDER: des1a1 des1a2 des1a des1b des1c1 extra1 des1c des1 ip1a ipcommon ip1 ip2a ip2b ip2c ip2 top1 ip3 top2

Perl 6

<lang perl6>sub top_topos ( %deps, *@top ) {

   my %ba;
   for %deps.kv -> $after, @befores {
       for @befores -> $before {
           %ba{$after}{$before} = 0 if $before ne $after;
           %ba{$before} //= {};
       }
   }
   if @top {

my @want = @top; my %care; %care{@want} = 1 xx *; repeat while @want { my @newwant; for @want -> $before { if %ba{$before} { for %ba{$before}.keys -> $after { if not %ba{$before}{$after} { %ba{$before}{$after}++; push @newwant, $after; } } } } @want = @newwant; %care{@want} = 1 xx *; }

for %ba.keys -> $before { %ba{$before}:delete unless %care{$before}; }

   }

   my @levels;
   while %ba.grep( not *.value )».key -> @befores {

push @levels, ~@befores.sort;

       %ba{@befores}:delete;
       for %ba.values { .{@befores}:delete }
   }
   if @top {

say "For top-level-modules: ", @top; say " $_" for @levels;

   }
   else {

say "Top levels are: @levels[*-1]";

   }

   say "Cycle found! {%ba.keys.sort}" if %ba;
   say ; 

}

my %deps =

   top1  =>  <des1 ip1 ip2>,
   top2  =>  <des1 ip2 ip3>,
   ip1   =>  <extra1 ip1a ipcommon>,
   ip2   =>  <ip2a ip2b ip2c ipcommon>,
   des1  =>  <des1a des1b des1c>,
   des1a =>  <des1a1 des1a2>,
   des1c =>  <des1c1 extra1>;
    

top_topos(%deps); top_topos(%deps, 'top1'); top_topos(%deps, 'top2'); top_topos(%deps, 'ip1'); top_topos(%deps, 'top1', 'top2');</lang>

Output:
Top levels are: top1 top2

For top-level-modules: top1
  des1a1 des1a2 des1b des1c1 extra1 ip1a ip2a ip2b ip2c ipcommon
  des1a des1c ip1 ip2
  des1
  top1

For top-level-modules: top2
  des1a1 des1a2 des1b des1c1 extra1 ip2a ip2b ip2c ip3 ipcommon
  des1a des1c ip2
  des1
  top2

For top-level-modules: ip1
  extra1 ip1a ipcommon
  ip1

For top-level-modules: top1 top2
  des1a1 des1a2 des1b des1c1 extra1 ip1a ip2a ip2b ip2c ip3 ipcommon
  des1a des1c ip1 ip2
  des1
  top1 top2

Phix

Minor tweaks to the Topological_sort code: top_levels, propagate() and -1 now means "not required". <lang Phix>sequence names enum RANK, NAME, DEP -- content of names -- rank is 1 for items to compile first, then 2, etc, -- or 0 if cyclic dependencies prevent compilation. -- - and -1 now means "not required". -- name is handy, and makes the result order alphabetic! -- dep is a list of dependencies (indexes to other names)

function add_dependency(string name)

   integer k = find(name,vslice(names,NAME))
   if k=0 then
       names = append(names,{-1,name,{}})
       k = length(names)
   end if
   return k

end function

procedure propagate(integer t)

   if names[t][RANK]!=0 then
       names[t][RANK] = 0
       for i=1 to length(names[t][DEP]) do
           propagate(names[t][DEP][i])
       end for
   end if

end procedure

procedure topsort(string input, sequence tops)

   names = {}
   sequence lines = split(input,'\n')
   for i=1 to length(lines) do
       sequence line = split(lines[i],no_empty:=true),
                dependencies = {}
       integer k = add_dependency(line[1])
       for j=2 to length(line) do
           integer l = add_dependency(line[j])
           if l!=k then -- ignore self-references
               dependencies &= l
           end if
       end for
       names[k][DEP] = dependencies
   end for
   if tops={} then
       -- show top levels
       for i=1 to length(names) do
           for j=1 to length(names[i][DEP]) do
               integer ji = names[i][DEP][j]
               names[ji][RANK] = 0
           end for
       end for
       sequence top_levels = {}
       for i=1 to length(names) do
           if names[i][RANK]=-1 then
               top_levels = append(top_levels,names[i][NAME])
           end if      
       end for
       printf(1,"top levels: %s\n",{join(top_levels)})
       return
   end if
   -- Propagate required by setting RANK to 0:
   for i=1 to length(tops) do
       integer t = add_dependency(tops[i])
       propagate(t)
   end for
   
   -- Now populate names[RANK] iteratively:
   bool more = true
   integer rank = 0
   while more do
       more = false 
       rank += 1
       for i=1 to length(names) do
           if names[i][RANK]=0 then
               bool ok = true
               for j=1 to length(names[i][DEP]) do
                   integer ji = names[i][DEP][j],
                           nr = names[ji][RANK]
                   if nr=0 or nr=rank then
                       -- not yet compiled, or same pass
                       ok = false
                       exit
                   end if
               end for
               if ok then
                   names[i][RANK] = rank
                   more = true
               end if
           end if
       end for
   end while
   names = sort(names) -- (ie by [RANK=1] then [NAME=2])
   integer prank = -1
   for i=1 to length(names) do
       rank = names[i][RANK]
       if rank>-1 then
           puts(1,iff(rank=prank?" ":sprintf("\nlevel %d:",rank)))
           puts(1,names[i][NAME])
           prank = rank
       end if
   end for
   puts(1,"\n")

end procedure

constant input = """ top1 des1 ip1 ip2 top2 des1 ip2 ip3 ip1 extra1 ip1a ipcommon ip2 ip2a ip2b ip2c ipcommon des1 des1a des1b des1c des1a des1a1 des1a2 des1c des1c1 extra1"""

topsort(input,{}) topsort(input,{"top1"}) topsort(input,{"top2"}) topsort(input,{"top1","top2"}) topsort(input,{"ip1"})</lang>

Output:

Items on the same line can be compiled at the same time, and each line is alphabetic.

top levels: top1 top2

level 1:des1a1 des1a2 des1b des1c1 extra1 ip1a ip2a ip2b ip2c ipcommon
level 2:des1a des1c ip1 ip2
level 3:des1
level 4:top1

level 1:des1a1 des1a2 des1b des1c1 extra1 ip2a ip2b ip2c ip3 ipcommon
level 2:des1a des1c ip2
level 3:des1
level 4:top2

level 1:des1a1 des1a2 des1b des1c1 extra1 ip1a ip2a ip2b ip2c ip3 ipcommon
level 2:des1a des1c ip1 ip2
level 3:des1
level 4:top1 top2

level 1:extra1 ip1a ipcommon
level 2:ip1

Python

Where the compile order between a subset of files is arbitrary, they are shown on the same line. <lang python>try:

   from functools import reduce

except: pass

  1. Python 3.x: def topx(data:'dict', tops:'set'=None) -> 'list':

def topx(data, tops=None):

   'Extract the set of top-level(s) in topological order'
   for k, v in data.items():
       v.discard(k) # Ignore self dependencies
   if tops is None:
       tops = toplevels(data)
   return _topx(data, tops, [], set())

def _topx(data, tops, _sofar, _sofar_set):

   'Recursive topological extractor'
   _sofar += [tops] # Accumulates order in reverse
   _sofar_set.union(tops)
   depends = reduce(set.union, (data.get(top, set()) for top in tops))
   if depends:
       _topx(data, depends, _sofar, _sofar_set)
   ordered, accum = [], set()
   for s in _sofar[::-1]:
       ordered += [sorted(s - accum)]
       accum |= s
   return ordered

def printorder(order):

   'Prettyprint topological ordering'
   if order:
       print("First: " + ', '.join(str(s) for s in order[0]))
   for o in order[1:]:
       print(" Then: " + ', '.join(str(s) for s in o))

def toplevels(data):

   \
   Extract all top levels from dependency data
   Top levels are never dependents
   
   for k, v in data.items():
       v.discard(k) # Ignore self dependencies
   dependents = reduce(set.union, data.values())
   return  set(data.keys()) - dependents

if __name__ == '__main__':

   data = dict(
       top1  = set('ip1 des1 ip2'.split()),
       top2  = set('ip2 des1 ip3'.split()),
       des1  = set('des1a des1b des1c'.split()),
       des1a = set('des1a1 des1a2'.split()),
       des1c = set('des1c1 extra1'.split()),
       ip2   = set('ip2a ip2b ip2c ipcommon'.split()),
       ip1   = set('ip1a ipcommon extra1'.split()),
       )
   tops = toplevels(data)
   print("The top levels of the dependency graph are: " + ' '.join(tops))
   for t in sorted(tops):
       print("\nThe compile order for top level: %s is..." % t)
       printorder(topx(data, set([t])))
   if len(tops) > 1:
       print("\nThe compile order for top levels: %s is..."
             % ' and '.join(str(s) for s in sorted(tops)) )
       printorder(topx(data, tops))</lang>

Sample Output

The top levels of the dependency graph are: top2 top1

The compile order for top level: top1 is...
First: des1a1, des1a2, des1c1, extra1
 Then: des1a, des1b, des1c, ip1a, ip2a, ip2b, ip2c, ipcommon
 Then: des1, ip1, ip2
 Then: top1

The compile order for top level: top2 is...
First: des1a1, des1a2, des1c1, extra1
 Then: des1a, des1b, des1c, ip2a, ip2b, ip2c, ipcommon
 Then: des1, ip2, ip3
 Then: top2

The compile order for top levels: top1 and top2 is...
First: des1a1, des1a2, des1c1, extra1
 Then: des1a, des1b, des1c, ip1a, ip2a, ip2b, ip2c, ipcommon
 Then: des1, ip1, ip2, ip3
 Then: top1, top2

Racket

<lang racket>#lang racket (define dep-tree ; go straight for the hash, without parsing strings etc.

 #hash((top1  . (des1 ip1 ip2))
       (top2  . (des1 ip2 ip3))
       (ip1   . (extra1 ip1a ipcommon))
       (ip2   . (ip2a ip2b ip2c ipcommon))
       (des1  . (des1a des1b des1c))
       (des1a . (des1a1 des1a2))
       (des1c . (des1c1 extra1))))

(define (build-tree Deps Top)

 (define (build n b# d)
   (hash-set b# n d))  
 
 (define (inner-b-t node visited built# depth)
   (cond
     [(hash-ref built# node #f)
      built#]
     [(member node visited)
      (error 'build-tree "circular dependency tree at node: ~a" node)]
     [(hash-ref Deps node #f)
      =>
      (λ (deps)
        (define built#+
          (for/fold ((built# built#)) ((dependency deps))
            (if (equal? dependency node)
                built#
                (inner-b-t dependency (cons node visited) built# (add1 depth)))))
        (build node built#+ depth))]
     [else
      (build node built# depth)]))
 
 (define final-build# (inner-b-t Top null (hash) 1))
 
 (define levels# (for/fold ((hsh# (hash))) (([k v] (in-hash final-build#)))
                   (hash-update hsh# v (curry cons k) null)))
 (for/list ((lvl (in-list (sort (hash-keys levels#) >))))
   (hash-ref levels# lvl)))

(define (print-build-order Deps Top)

 (define build-order (build-tree Deps Top))
 (printf "To build: ~s~%" Top)
 (for ((round build-order)) (printf "Build: ~a~%" round))
 (newline))

(print-build-order dep-tree 'top1) (print-build-order dep-tree 'top2) (with-handlers [(exn? (λ (x) (displayln (exn-message x) (current-error-port))))]

 (build-tree #hash((top . (des1 ip1)) (ip1 . (net netip)) (netip . (mac ip1))) 'top))</lang>
Output:
To build: top1
Build: (extra1 des1c1 des1a2 des1a1)
Build: (ip2c ip2b ip2a ipcommon ip1a des1b des1c des1a)
Build: (des1 ip2 ip1)
Build: (top1)

To build: top2
Build: (extra1 des1c1 des1a2 des1a1)
Build: (ip2c ip2b ip2a ipcommon des1b des1c des1a)
Build: (ip3 des1 ip2)
Build: (top2)

build-tree: circular dependency tree at node: ip1

REXX

Where the compile order between a subset of files is arbitrary, they are shown on the same line.
This REXX version can handle multiple top levels. <lang REXX>/*REXX program displays the compile order of jobs (indicating the dependencies). */ parse arg job /*obtain optional argument from the CL.*/ jobL. =; stage.=; #.=0; @.=; JL= /*define some handy─dandy variables. */ tree. =; tree.1= ' top1 des1 ip1 ip2 '

                            tree.2= '  top2     des1      ip2       ip3                 '
                            tree.3= '  ip1      extra1    ip1a      ipcommon            '
                            tree.4= '  ip2      ip2a      ip2b      ip2c       ipcommon '
                            tree.5= '  des1     des1a     des1b     des1c               '
                            tree.6= '  des1a    des1a1    des1a2                        '
                            tree.7= '  des1c    des1c1    extra1                        '

$=

             do j=1  while  tree.j\==                               /*build job tree.*/
             parse var tree.j x deps;           @.x=space(deps)       /*extract jobs.  */
             if wordpos(x, $)==0  then $=$ x                          /*Unique? Add it.*/
                      do k=1  for words(@.x);   _=word(@.x, k)
                      if wordpos(_, $)==0  then $=space($ _)
                      end   /*k*/
             end            /*j*/

!.=;  !!.=

             do j=1      for words($);      x=word($, j);         !.x.0=words(@.x)
                 do k=1  for !.x.0;     !.x.k=word(@.x, k);      !!.x.k=!.x.k
                 end   /*k*/                    /* [↑]  build arrays of job departments*/
             end       /*j*/
 do words($)                                    /*process all the jobs specified.      */
     do j=1  for words($);      x=word($, j);       z=words(@.x);       allN=1;      m=0
     if z==0  then do;  #.x=1;  iterate;  end   /*if no dependents, then skip this one.*/
        do k=1  for z;   y=!.x.k                /*examine all the stage numbers.       */
        if datatype(y, 'W')  then m=max(m, y)   /*find the highest stage number.       */
                             else do;  allN=0   /*at least one entry isn't  numeric.   */
                                       if #.y\==0  then !.x.k=#.y
                                  end           /* [↑]  replace with a number.         */
        end   /*k*/
     if allN & m\==0  then #.x=max(#.x, m + 1)  /*replace with the stage number max.   */
     end     /*j*/                              /* [↑]  maybe set the stage number.    */
 end         /*words($)*/

if job= then job=word(tree.1, 1) /*Not specified? Use 1st job in tree.*/ jobL.1=job /*define the bottom level jobList. */ s=1 /*define the stage level for jobList. */

       do j=1;              yyy=jobL.j
          do r=1  for words(yyy)                /*verify that there are no duplicates. */
              do c=1  while c<words(yyy);            z=word(yyy,c)
              p=wordpos(z, yyy, c + 1);    if p\==0  then yyy=delword(yyy, p, 1)
              end   /*c*/                       /* [↑]   Duplicate?    Then delete it. */
          end       /*r*/
       jobL.j=yyy
       if yyy=  then leave                    /*if null, then we're done with jobList*/
       z=words(yyy)                             /*number of jobs in the jobList.       */
       s=s+1                                    /*bump the stage number.               */
             do k=1  for z;   _=word(yyy, k)    /*obtain a stage number for the job.   */
             jobL.s=jobL.s  @._                 /*add a job to a stage.                */
             end   /*k*/
       end         /*j*/
  do k=1  for s;   JL=JL jobL.k;   end  /*k*/   /*build a complete jobList  (JL).      */
  do s=1  for words(JL)                         /*process each job in the  jobList.    */
  _=word(JL, s);     level=#._                  /*get the proper level for the job.    */
  stage.level= stage.level _                    /*assign a level to job stage number.  */
  end   /*s*/                                   /* [↑]  construct various job stages.  */

say '─────── The compile order for job: ' job " ────────"; say

                                                /* [↓]  display the stages for the job.*/
  do show=1  for s;     if stage.show\==  then say show stage.show
  end   /*show*/                                /*stick a fork in it,  we're all done. */</lang>
output   when using the default input of:   top1
───────  The compile order for job:  top1  ─────── 

1  des1b extra1 ip1a ipcommon ip2a ip2b ip2c des1a1 des1a2 des1c1 extra1
2  ip1 ip2 des1a des1c
3  des1
4  top1
output   when using the input of:   top2
───────  The compile order for job:  top2  ───────

1  ip3 des1b ip2a ip2b ip2c ipcommon des1a1 des1a2 des1c1 extra1
2  ip2 des1a des1c
3  des1
4  top2
output   when using the input of:   top1 top2
───────  The compile order for job:  top1 top2  ───────

1  ip3 des1b extra1 ip1a ipcommon ip2a ip2b ip2c des1a1 des1a2 des1c1 extra1
2  ip1 ip2 des1a des1c
3  des1
4  top1 top2

Tcl

The topsort proc is taken from Topological sort#Tcl with {*} removed from the line commented so that results are returned by level:

<lang Tcl>package require Tcl 8.5 proc topsort {data} {

   # Clean the data
   dict for {node depends} $data {
       if {[set i [lsearch -exact $depends $node]] >= 0} {
           set depends [lreplace $depends $i $i]
           dict set data $node $depends
       }
       foreach node $depends {dict lappend data $node}
   }
   # Do the sort
   set sorted {}
   while 1 {
       # Find available nodes
       set avail [dict keys [dict filter $data value {}]]
       if {![llength $avail]} {
           if {[dict size $data]} {
               error "graph is cyclic, possibly involving nodes \"[dict keys $data]\""
           }
           return $sorted
       }
       lappend sorted $avail   ;# change here: Topological sort had {*}$avail
       # Remove from working copy of graph
       dict for {node depends} $data {
           foreach n $avail {
               if {[set i [lsearch -exact $depends $n]] >= 0} {
                   set depends [lreplace $depends $i $i]
                   dict set data $node $depends
               }
           }
       }
       foreach node $avail {
           dict unset data $node
       }
   }

}

  1. The changes to $data in this proc offer an interesting reflection on value semantics.
  2. Consider the value of $data seen by [dict for], by each invocation of [dict keys]
  3. and [dict unset] and how that affects the soundness of the loops.

proc tops {data} {

   dict for {k v} $data {
       foreach t [dict keys $data] {
           if {$t in $v} {
               dict unset data $t
           }
       }
   }
   dict keys $data

}

proc withdeps {dict tops {res {}}} {

   foreach top $tops {
       if {[dict exists $dict $top]} {
           set deps [dict get $dict $top]
           set res [dict merge  $res  [dict create $top $deps]  [withdeps $dict $deps]]
       }
   }
   return $res

}

proc parsetop {t} {

   set top {}
   foreach l [split $t \n] {
       catch {dict lappend top {*}$l}
   }
   return $top

}

set inputData {

       top1    des1 ip1 ip2
       top2    des1 ip2 ip3
       ip1     extra1 ip1a ipcommon
       ip2     ip2a ip2b ip2c ipcommon
       des1    des1a des1b des1c
       des1a   des1a1 des1a2
       des1c   des1c1 extra1

}

set d [parsetop $inputData] pdict $d set tops [tops $d]

puts "Tops: $tops\n"

set targets [list $tops {*}$tops] foreach target $targets {

   puts "Target: $target"
   set i 0
   foreach deps [topsort [withdeps $d $target]] {
       puts "\tround [incr i]:\t$deps"
   }

}</lang>

Output:
Tops: top1 top2

Target: top1 top2
        round 1:        des1b des1a1 des1a2 des1c1 extra1 ip1a ipcommon ip2a ip2b ip2c ip3
        round 2:        des1a des1c ip1 ip2
        round 3:        des1
        round 4:        top1 top2
Target: top1
        round 1:        des1b des1a1 des1a2 des1c1 extra1 ip1a ipcommon ip2a ip2b ip2c
        round 2:        des1a des1c ip1 ip2
        round 3:        des1
        round 4:        top1
Target: top2
        round 1:        ip3 des1b des1a1 des1a2 des1c1 extra1 ip2a ip2b ip2c ipcommon
        round 2:        des1a des1c ip2
        round 3:        des1
        round 4:        top2