--- /dev/null
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module coloring
+
+import poset
+
+# Build a conflict graph from a POSet
+class POSetConflictGraph[E: Object]
+
+ # Core is composed by:
+ # * elements that have mutiple direct parents
+ # * parents of elements that have multiple direct parents
+ # REQUIRE: is_colored
+ var core = new HashSet[E]
+
+ # Border is composed by minimal elements of the core:
+ # * that have multiple direct parents
+ # * but whose subelements are all in single inheritance
+ # REQUIRE: is_colored
+ var border = new HashSet[E]
+
+ # The crown is composed by the elements that are:
+ # * not part of the core nor the border
+ # * are in single inheritance
+ # REQUIRE: is_colored
+ var crown = new HashSet[E]
+
+ # Conflict graph of the POSet
+ # Elements X and Y are in conflict if either:
+ # * X and Y are the same element
+ # * Y is a subelement of X
+ # * X and Y have common sub elements
+ # REQUIRE: is_colored
+ var conflicts = new HashMap[E, Set[E]]
+
+ var poset: POSet[E]
+
+ init(poset: POSet[E]) do
+ self.poset = poset
+ extract_core
+ extract_border
+ extract_crown
+ compute_conflicts
+ end
+
+ # Compute the set of elements forming the core of the poset hierarchy.
+ private fun extract_core do
+ core.clear
+ for e in poset do
+ if poset[e].direct_greaters.length > 1 then
+ core.add_all(poset[e].greaters)
+ end
+ end
+ end
+
+ # Compute the set of elements composing the border of the core
+ # Elements belonging to the `border` are removed from the `core`
+ private fun extract_border do
+ border.clear
+ for e in core do
+ if not is_border(e) then continue
+ border.add(e)
+ end
+ for e in border do core.remove(e)
+ end
+
+ private fun is_border(e: E): Bool do
+ for child in poset[e].direct_smallers do
+ if core.has(child) then return false
+ end
+ return true
+ end
+
+ # Compute the set of elements belonging to the crown of the inheritance hierarchy.
+ private fun extract_crown do
+ crown.clear
+ for e in poset do
+ if not core.has(e) and not border.has(e) then crown.add(e)
+ end
+ end
+
+ # Check for conflict in the core.
+ # Start from border and tag every ancestors
+ private fun compute_conflicts do
+ conflicts.clear
+ for e in border do add_conflicts(poset[e].greaters)
+ end
+
+ private fun add_conflict(e, o: E) do
+ if not conflicts.has_key(e) then conflicts[e] = new HashSet[E]
+ if not conflicts.has_key(o) then conflicts[o] = new HashSet[E]
+ conflicts[e].add(o)
+ conflicts[o].add(e)
+ end
+
+ private fun add_conflicts(es: Collection[E]) do
+ for e1 in es do
+ for e2 in es do add_conflict(e1, e2)
+ end
+ end
+
+ # Used for debugging only
+ fun pretty_print do
+ #print "core: {core.join(" ")} ({core.length})"
+ #print "border: {border.join(" ")} ({border.length})"
+ #print "crown: {crown.join(" ")} ({crown.length})"
+ print "conflicts:"
+ for e, c in conflicts do print " {e}: {c.join(" ")}"
+ end
+end
+
+# Colorize elements from a POSet
+# Two elements from a POSet cannot have the same color if they share common subelements
+#
+# Example:
+# A
+# / | \
+# / | \
+# B C D
+# | /| |
+# | / | |
+# |/ | |
+# E F G
+# |
+# H
+# Conflicts:
+# A: {B, C, D, E, F, G, H}
+# B: {A, C, E, H}
+# C: {A, E, H, F}
+# D: {A, G}
+# E: {A, B, C, H}
+# F: {A, C}
+# G: {A, D}
+# H: {A, B, C, E}
+# Possible colors:
+# A:0, B:1, C: 2, D: 1, E: 3, F:3, G:2, H:4
+#
+# see:
+# Ducournau, R. (2011).
+# Coloring, a versatile technique for implementing object-oriented languages.
+# Software: Practice and Experience, 41(6), 627–659.
+class POSetColorer[E: Object]
+
+ # Is the poset already colored?
+ var is_colored = false
+
+ # Resulting ids
+ # REQUIRE: is_colored
+ fun ids: Map[E, Int] do
+ assert is_colored
+ return ids_cache
+ end
+ private var ids_cache = new HashMap[E, Int]
+
+ # Resulting colors
+ # REQUIRE: is_colored
+ fun colors: Map[E, Int] do
+ assert is_colored
+ return colors_cache
+ end
+ private var colors_cache = new HashMap[E, Int]
+
+ # REQUIRE: is_colored
+ fun poset: POSet[E] do
+ assert is_colored
+ return poset_cache
+ end
+ private var poset_cache: POSet[E]
+
+ # REQUIRE: is_colored
+ fun conflicts: Map[E, Set[E]] do
+ assert is_colored
+ return conflicts_cache
+ end
+ private var conflicts_cache: Map[E, Set[E]]
+
+ private var graph: POSetConflictGraph[E]
+
+ init do end
+
+ # Start coloring on given POSet
+ fun colorize(poset: POSet[E]) do
+ poset_cache = poset
+ graph = new POSetConflictGraph[E](poset)
+ allocate_ids
+ compute_colors
+ conflicts_cache = graph.conflicts
+ is_colored = true
+ end
+
+ private fun allocate_ids do
+ ids_cache.clear
+ var elements = new HashSet[E].from(poset_cache.to_a)
+ for e in poset_cache.linearize(elements) do
+ ids_cache[e] = ids_cache.length
+ end
+ end
+
+ # Colorize core, border and crown in that order
+ private fun compute_colors do
+ colors_cache.clear
+ colorize_core
+ colorize_set(graph.border)
+ colorize_set(graph.crown)
+ end
+
+ # Core elements cannot have the same color than:
+ # * one of their parents
+ # * one of their conflicting elements
+ private fun colorize_core do
+ for e in poset_cache.linearize(graph.core) do
+ var color = min_color(e)
+ var conflicts = graph.conflicts[e]
+ while not is_color_free(color, conflicts) do
+ color += 1
+ end
+ colors_cache[e] = color
+ end
+ end
+
+ # Other elements inherit color fron their direct parents
+ private fun colorize_set(set: Set[E]) do
+ for e in poset_cache.linearize(set) do colors_cache[e] = min_color(e)
+ end
+
+ # Get the next minimal color from direct parents
+ private fun min_color(e: E): Int do
+ var max_color = -1
+ for p in poset_cache[e].direct_greaters do
+ if not colors_cache.has_key(p) then continue
+ var color = colors_cache[p]
+ if color > max_color then max_color = color
+ end
+ return max_color + 1
+ end
+
+ private fun is_color_free(color: Int, set: Collection[E]): Bool do
+ for e in set do
+ if colors_cache.has_key(e) and colors_cache[e] == color then return false
+ end
+ return true
+ end
+
+ # Used for debugging only
+ fun pretty_print do
+ print "ids:"
+ for e, id in ids do print " {e}: {id}"
+ print "colors:"
+ for e, c in colors do print " {e}: {c}"
+ end
+end
+
+# Colorize a collection of buckets
+# Two elements cannot have the same color if they both appear in the same bucket
+# No coloring order is garantied
+#
+# Example:
+# buckets[A] = {x1, x2}
+# buckets[B] = {x1, x3, x4}
+# buckets[C] = {x2, x3}
+# Conflicts:
+# x1: {x2, x3, x4}
+# x2: {x1, x3}
+# x3: {x1, x2, x4}
+# x4: {x1, x3}
+# Possible colors:
+# x1: 0, x2: 1, x3: 2, x4: 1
+class BucketsColorer[H: Object, E: Object]
+ private var colors = new HashMap[E, Int]
+ private var conflicts = new HashMap[E, Set[E]]
+
+ init do end
+
+ # Start bucket coloring
+ fun colorize(buckets: Map[H, Set[E]]): Map[E, Int] do
+ compute_conflicts(buckets)
+ var min_color = 0
+ for holder, hbuckets in buckets do
+ for bucket in hbuckets do
+ if colors.has_key(bucket) then continue
+ var color = min_color
+ while not is_color_free(bucket, color) do
+ color += 1
+ end
+ colors[bucket] = color
+ color = min_color
+ end
+ end
+ return colors
+ end
+
+ private fun is_color_free(bucket: E, color: Int): Bool do
+ if conflicts.has_key(bucket) then
+ for other in conflicts[bucket] do
+ if colors.has_key(other) and colors[other] == color then return false
+ end
+ end
+ return true
+ end
+
+ private fun compute_conflicts(buckets: Map[H, Set[E]]) do
+ conflicts.clear
+ for holder, hbuckets in buckets do
+ for bucket in hbuckets do
+ if not conflicts.has_key(bucket) then conflicts[bucket] = new HashSet[E]
+ for obucket in hbuckets do
+ if obucket == bucket then continue
+ if not conflicts.has_key(obucket) then conflicts[obucket] = new HashSet[E]
+ conflicts[bucket].add(obucket)
+ conflicts[obucket].add(bucket)
+ end
+ end
+ end
+ end
+end
+
+# Colorize a collection of buckets using a poset and a conflict graph
+# Two elements cannot have the same color if they both appear in the same bucket
+# The use of a POSet hierarchy optimize the coloring
+# Buckets elements are colored using linearization order starting
+class POSetBucketsColorer[H: Object, E: Object]
+ private var colors = new HashMap[E, Int]
+ private var poset: POSet[H]
+ private var conflicts: Map[H, Set[H]]
+
+ init(poset: POSet[H], conflicts: Map[H, Set[H]]) do
+ self.poset = poset
+ self.conflicts = conflicts
+ end
+
+ # Colorize buckets using the POSet and conflict graph
+ fun colorize(buckets: Map[H, Set[E]]): Map[E, Int] do
+ colors.clear
+ for h in poset.linearize(buckets.keys) do
+ var color = min_color(poset[h].direct_greaters, buckets)
+ for bucket in buckets[h] do
+ if colors.has_key(bucket) then continue
+ while not is_color_free(color, h, buckets) do color += 1
+ colors[bucket] = color
+ color += 1
+ end
+ end
+ return colors
+ end
+
+ # Get the next available color considering used colors by other buckets
+ private fun min_color(others: Collection[H], buckets: Map[H, Set[E]]): Int do
+ var min = -1
+ for holder in others do
+ var color = max_color(holder, buckets)
+ if color > min then min = color
+ end
+ return min + 1
+ end
+
+ # Return the max color used by a class
+ private fun max_color(holder: H, buckets: Map[H, Set[E]]): Int do
+ var max = -1
+ for bucket in buckets[holder] do
+ if not colors.has_key(bucket) then continue
+ var color = colors[bucket]
+ if color > max then max = color
+ end
+ return max
+ end
+
+ # Check if the color is free for this holder
+ private fun is_color_free(color: Int, holder: H, buckets: Map[H, Set[E]]): Bool do
+ if not conflicts.has_key(holder) then return true
+ for conflict in conflicts[holder] do
+ for bucket in buckets[conflict] do
+ if not colors.has_key(bucket) then continue
+ if colors[bucket] == color then return false
+ end
+ end
+ return true
+ end
+end
+
+
nitlanguage / nit.git / commitdiff