mirror of https://gitee.com/bigwinds/arangodb
102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2016 ArangoDB GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Simon Grätzer
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////////////////////////////////////////////////////////////////////////////////
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#include "PageRank.h"
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#include "Pregel/Aggregator.h"
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#include "Pregel/GraphFormat.h"
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#include "Pregel/Iterators.h"
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#include "Pregel/MasterContext.h"
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#include "Pregel/Utils.h"
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#include "Pregel/VertexComputation.h"
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using namespace arangodb;
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using namespace arangodb::pregel;
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using namespace arangodb::pregel::algos;
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static float EPS = 0.00001;
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static std::string const kConvergence = "convergence";
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PageRank::PageRank(VPackSlice const& params)
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: SimpleAlgorithm("PageRank", params) {
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_maxGSS =
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basics::VelocyPackHelper::getNumericValue(params, "maxIterations", 250);
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}
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struct PRComputation : public VertexComputation<float, float, float> {
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PRComputation() {}
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void compute(MessageIterator<float> const& messages) override {
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float* ptr = mutableVertexData();
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float copy = *ptr;
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if (globalSuperstep() == 0) {
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*ptr = 1.0 / context()->vertexCount();
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} else {
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float sum = 0.0;
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for (const float* msg : messages) {
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sum += *msg;
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}
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*ptr = 0.85 * sum + 0.15 / context()->vertexCount();
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}
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float diff = fabs(copy - *ptr);
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aggregate<float>(kConvergence, diff);
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RangeIterator<Edge<float>> edges = getEdges();
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float val = *ptr / edges.size();
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for (Edge<float>* edge : edges) {
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sendMessage(edge, val);
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}
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}
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};
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VertexComputation<float, float, float>* PageRank::createComputation(
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WorkerConfig const* config) const {
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return new PRComputation();
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}
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IAggregator* PageRank::aggregator(std::string const& name) const {
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if (name == kConvergence) {
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return new MaxAggregator<float>(-1, false);
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}
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return nullptr;
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}
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struct PRMasterContext : public MasterContext {
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float _threshold = EPS;
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PRMasterContext(VPackSlice params) {
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VPackSlice t = params.get("threshold");
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_threshold = t.isNumber() ? t.getNumber<float>() : EPS;
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}
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void preApplication() override {
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LOG_TOPIC(INFO, Logger::PREGEL) << "Using threshold " << _threshold;
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};
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bool postGlobalSuperstep() override {
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float const* diff = getAggregatedValue<float>(kConvergence);
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return globalSuperstep() < 1 || *diff > _threshold;
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};
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};
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MasterContext* PageRank::masterContext(VPackSlice userParams) const {
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return new PRMasterContext(userParams);
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}
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