graph: Add 'shortest-path'.
* guix/graph.scm (shortest-path): New procedure.
* tests/graph.scm ("shortest-path, packages + derivations")
("shortest-path, reverse packages")
("shortest-path, references"): New tests.
This commit is contained in:
Ludovic Courtès
parent
7240202136
commit
36c2192414
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@ -1,5 +1,5 @@
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;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2015, 2016, 2020 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2016 Ricardo Wurmus <rekado@elephly.net>
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;;;
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;;; This file is part of GNU Guix.
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@ -42,6 +42,7 @@
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traverse/depth-first
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node-transitive-edges
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node-reachable-count
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shortest-path
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%graph-backends
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%d3js-backend
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@ -140,6 +141,72 @@ typically returned by 'node-edges' or 'node-back-edges'."
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0
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nodes node-edges))
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(define (shortest-path node1 node2 type)
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"Return as a monadic value the shorted path, represented as a list, from
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NODE1 to NODE2 of the given TYPE. Return #f when there is no path."
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(define node-edges
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(node-type-edges type))
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(define (find-shortest lst)
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;; Return the shortest path among LST, where each path is represented as a
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;; vlist.
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(let loop ((lst lst)
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(best +inf.0)
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(shortest #f))
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(match lst
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(()
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shortest)
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((head . tail)
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(let ((len (vlist-length head)))
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(if (< len best)
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(loop tail len head)
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(loop tail best shortest)))))))
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(define (find-path node path paths)
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;; Return the a vhash that maps nodes to paths, with each path from the
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;; given node to NODE2.
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(define (augment-paths child paths)
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;; When using %REFERENCE-NODE-TYPE, nodes can contain self references,
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;; hence this test.
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(if (eq? child node)
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(store-return paths)
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(find-path child vlist-null paths)))
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(cond ((eq? node node2)
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(store-return (vhash-consq node (vlist-cons node path)
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paths)))
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((vhash-assq node paths)
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(store-return paths))
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(else
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;; XXX: We could stop recursing if one if CHILDREN is NODE2, but in
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;; practice it's good enough.
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(mlet* %store-monad ((children (node-edges node))
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(paths (foldm %store-monad
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augment-paths
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paths
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children)))
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(define sub-paths
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(filter-map (lambda (child)
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(match (vhash-assq child paths)
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(#f #f)
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((_ . path) path)))
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children))
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(match sub-paths
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(()
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(return (vhash-consq node #f paths)))
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(lst
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(return (vhash-consq node
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(vlist-cons node (find-shortest sub-paths))
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paths))))))))
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(mlet %store-monad ((paths (find-path node1
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(vlist-cons node1 vlist-null)
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vlist-null)))
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(return (match (vhash-assq node1 paths)
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((_ . #f) #f)
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((_ . path) (vlist->list path))))))
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;;;
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;;; Graphviz export.
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@ -398,4 +398,65 @@ edges."
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(return (list (node-reachable-count (list p2) edges)
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(node-reachable-count (list p0) back)))))))
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(test-equal "shortest-path, packages + derivations"
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'(("p5" "p4" "p1" "p0")
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("p3" "p2" "p1" "p0")
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#f
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("p5-0.drv" "p4-0.drv" "p1-0.drv" "p0-0.drv"))
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(run-with-store %store
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(let* ((p0 (dummy-package "p0"))
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(p1 (dummy-package "p1" (inputs `(("p0" ,p0)))))
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(p2 (dummy-package "p2" (inputs `(("p1" ,p1)))))
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(p3 (dummy-package "p3" (inputs `(("p2" ,p2)))))
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(p4 (dummy-package "p4" (inputs `(("p1" ,p1)))))
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(p5 (dummy-package "p5" (inputs `(("p4" ,p4) ("p3" ,p3))))))
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(mlet* %store-monad ((path1 (shortest-path p5 p0 %package-node-type))
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(path2 (shortest-path p3 p0 %package-node-type))
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(nope (shortest-path p3 p4 %package-node-type))
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(drv5 (package->derivation p5))
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(drv0 (package->derivation p0))
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(path3 (shortest-path drv5 drv0
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%derivation-node-type)))
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(return (append (map (lambda (path)
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(and path (map package-name path)))
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(list path1 path2 nope))
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(list (map (node-type-label %derivation-node-type)
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path3))))))))
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(test-equal "shortest-path, reverse packages"
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'("libffi" "guile" "guile-json")
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(run-with-store %store
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(mlet %store-monad ((path (shortest-path (specification->package "libffi")
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guile-json
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%reverse-package-node-type)))
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(return (map package-name path)))))
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(test-equal "shortest-path, references"
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`(("d2" "d1" ,(package-full-name %bootstrap-guile "-"))
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(,(package-full-name %bootstrap-guile "-") "d1" "d2"))
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(run-with-store %store
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(mlet* %store-monad ((d0 (package->derivation %bootstrap-guile))
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(d1 (gexp->derivation "d1"
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#~(begin
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(mkdir #$output)
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(symlink #$%bootstrap-guile
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(string-append
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#$output "/l")))))
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(d2 (gexp->derivation "d2"
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#~(begin
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(mkdir #$output)
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(symlink #$d1
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(string-append
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#$output "/l")))))
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(_ (built-derivations (list d2)))
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(->node -> (node-type-convert %reference-node-type))
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(o2 (->node (derivation->output-path d2)))
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(o0 (->node (derivation->output-path d0)))
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(path (shortest-path (first o2) (first o0)
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%reference-node-type))
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(rpath (shortest-path (first o0) (first o2)
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%referrer-node-type)))
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(return (list (map (node-type-label %reference-node-type) path)
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(map (node-type-label %referrer-node-type) rpath))))))
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(test-end "graph")
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