123 lines
3.3 KiB
JavaScript
123 lines
3.3 KiB
JavaScript
"use strict";
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var _ = require("../lodash");
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module.exports = resolveConflicts;
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/*
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* Given a list of entries of the form {v, barycenter, weight} and a
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* constraint graph this function will resolve any conflicts between the
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* constraint graph and the barycenters for the entries. If the barycenters for
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* an entry would violate a constraint in the constraint graph then we coalesce
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* the nodes in the conflict into a new node that respects the contraint and
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* aggregates barycenter and weight information.
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*
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* This implementation is based on the description in Forster, "A Fast and
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* Simple Hueristic for Constrained Two-Level Crossing Reduction," thought it
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* differs in some specific details.
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*
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* Pre-conditions:
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*
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* 1. Each entry has the form {v, barycenter, weight}, or if the node has
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* no barycenter, then {v}.
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*
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* Returns:
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*
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* A new list of entries of the form {vs, i, barycenter, weight}. The list
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* `vs` may either be a singleton or it may be an aggregation of nodes
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* ordered such that they do not violate constraints from the constraint
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* graph. The property `i` is the lowest original index of any of the
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* elements in `vs`.
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*/
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function resolveConflicts(entries, cg) {
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var mappedEntries = {};
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_.forEach(entries, function(entry, i) {
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var tmp = mappedEntries[entry.v] = {
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indegree: 0,
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"in": [],
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out: [],
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vs: [entry.v],
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i: i
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};
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if (!_.isUndefined(entry.barycenter)) {
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tmp.barycenter = entry.barycenter;
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tmp.weight = entry.weight;
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}
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});
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_.forEach(cg.edges(), function(e) {
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var entryV = mappedEntries[e.v];
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var entryW = mappedEntries[e.w];
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if (!_.isUndefined(entryV) && !_.isUndefined(entryW)) {
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entryW.indegree++;
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entryV.out.push(mappedEntries[e.w]);
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}
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});
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var sourceSet = _.filter(mappedEntries, function(entry) {
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return !entry.indegree;
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});
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return doResolveConflicts(sourceSet);
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}
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function doResolveConflicts(sourceSet) {
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var entries = [];
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function handleIn(vEntry) {
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return function(uEntry) {
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if (uEntry.merged) {
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return;
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}
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if (_.isUndefined(uEntry.barycenter) ||
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_.isUndefined(vEntry.barycenter) ||
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uEntry.barycenter >= vEntry.barycenter) {
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mergeEntries(vEntry, uEntry);
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}
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};
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}
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function handleOut(vEntry) {
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return function(wEntry) {
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wEntry["in"].push(vEntry);
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if (--wEntry.indegree === 0) {
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sourceSet.push(wEntry);
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}
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};
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}
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while (sourceSet.length) {
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var entry = sourceSet.pop();
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entries.push(entry);
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_.forEach(entry["in"].reverse(), handleIn(entry));
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_.forEach(entry.out, handleOut(entry));
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}
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return _.map(_.filter(entries, function(entry) { return !entry.merged; }),
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function(entry) {
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return _.pick(entry, ["vs", "i", "barycenter", "weight"]);
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});
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}
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function mergeEntries(target, source) {
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var sum = 0;
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var weight = 0;
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if (target.weight) {
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sum += target.barycenter * target.weight;
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weight += target.weight;
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}
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if (source.weight) {
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sum += source.barycenter * source.weight;
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weight += source.weight;
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}
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target.vs = source.vs.concat(target.vs);
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target.barycenter = sum / weight;
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target.weight = weight;
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target.i = Math.min(source.i, target.i);
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source.merged = true;
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}
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