80 lines
2.1 KiB
JavaScript
80 lines
2.1 KiB
JavaScript
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"use strict";
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var _ = require("../lodash");
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var initOrder = require("./init-order");
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var crossCount = require("./cross-count");
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var sortSubgraph = require("./sort-subgraph");
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var buildLayerGraph = require("./build-layer-graph");
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var addSubgraphConstraints = require("./add-subgraph-constraints");
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var Graph = require("../graphlib").Graph;
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var util = require("../util");
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module.exports = order;
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/*
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* Applies heuristics to minimize edge crossings in the graph and sets the best
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* order solution as an order attribute on each node.
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*
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* Pre-conditions:
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*
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* 1. Graph must be DAG
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* 2. Graph nodes must be objects with a "rank" attribute
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* 3. Graph edges must have the "weight" attribute
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*
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* Post-conditions:
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*
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* 1. Graph nodes will have an "order" attribute based on the results of the
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* algorithm.
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*/
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function order(g) {
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var maxRank = util.maxRank(g),
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downLayerGraphs = buildLayerGraphs(g, _.range(1, maxRank + 1), "inEdges"),
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upLayerGraphs = buildLayerGraphs(g, _.range(maxRank - 1, -1, -1), "outEdges");
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var layering = initOrder(g);
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assignOrder(g, layering);
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var bestCC = Number.POSITIVE_INFINITY,
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best;
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for (var i = 0, lastBest = 0; lastBest < 4; ++i, ++lastBest) {
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sweepLayerGraphs(i % 2 ? downLayerGraphs : upLayerGraphs, i % 4 >= 2);
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layering = util.buildLayerMatrix(g);
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var cc = crossCount(g, layering);
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if (cc < bestCC) {
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lastBest = 0;
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best = _.cloneDeep(layering);
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bestCC = cc;
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}
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}
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assignOrder(g, best);
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}
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function buildLayerGraphs(g, ranks, relationship) {
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return _.map(ranks, function(rank) {
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return buildLayerGraph(g, rank, relationship);
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});
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}
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function sweepLayerGraphs(layerGraphs, biasRight) {
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var cg = new Graph();
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_.forEach(layerGraphs, function(lg) {
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var root = lg.graph().root;
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var sorted = sortSubgraph(lg, root, cg, biasRight);
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_.forEach(sorted.vs, function(v, i) {
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lg.node(v).order = i;
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});
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addSubgraphConstraints(lg, cg, sorted.vs);
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});
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}
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function assignOrder(g, layering) {
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_.forEach(layering, function(layer) {
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_.forEach(layer, function(v, i) {
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g.node(v).order = i;
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});
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});
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}
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