package edu.cmu.graphchi.vertexdata;
/**
* Copyright [2012] [Aapo Kyrola, Guy Blelloch, Carlos Guestrin / Carnegie Mellon University]
*
* 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.
*/
import edu.cmu.graphchi.datablocks.BytesToValueConverter;
import edu.cmu.graphchi.datablocks.ChiPointer;
import edu.cmu.graphchi.datablocks.DataBlockManager;
import edu.cmu.graphchi.datablocks.IntConverter;
import edu.cmu.graphchi.engine.auxdata.VertexData;
import edu.cmu.graphchi.preprocessing.VertexIdTranslate;
import java.io.*;
import java.util.Iterator;
/**
* Efficient iteration over vertex values for computing aggregates.
* @author Aapo Kyrola
*/
public class VertexAggregator {
/**
* Enumerate vertices using a callback
* @see edu.cmu.graphchi.vertexdata.ForeachCallback
* @param numVertices number of vertices in the graph (hint: use engine.numVertices())
* @param baseFilename name of the input graph
* @param conv converter object for converting bytes to vertex's value type
* @param callback your callback function
* @param <VertexDataType> vertex data type
* @throws IOException if the vertex data file is not found
*/
public static <VertexDataType> void foreach(int numVertices, String baseFilename, BytesToValueConverter<VertexDataType> conv,
ForeachCallback<VertexDataType> callback) throws IOException {
VertexData<VertexDataType> vertexData = new VertexData<VertexDataType>(numVertices, baseFilename, conv, true);
DataBlockManager blockManager = new DataBlockManager();
vertexData.setBlockManager(blockManager);
int CHUNK = 1000000;
for(int i=0; i < numVertices; i += CHUNK) {
int en = i + CHUNK;
if (en >= numVertices) en = numVertices - 1;
int blockId = vertexData.load(i, en);
Iterator<Integer> iter = vertexData.currentIterator();
while (iter.hasNext()) {
int j = iter.next();
ChiPointer ptr = vertexData.getVertexValuePtr(j, blockId);
VertexDataType value = blockManager.dereference(ptr, conv);
callback.callback(j, value);
}
}
}
/**
* Returns an iterator to vertices. Vertices are iterated in their internal-order,
* but the iterator elements have the original ids.
* @param numVertices number of vertices in the graph (hint: use engine.numVertices())
* @param baseFilename name of the input graph
* @param conv converter object for converting bytes to vertex's value type
* @param idTranslate translates ids from internal id to original id (use engine.getVertexIdTranslate())
* @param <VertexDataType>
* @return
*/
public static <VertexDataType> Iterator<VertexIdValue<VertexDataType> > vertexIterator(final int numVertices,
String baseFilename,
final BytesToValueConverter<VertexDataType> conv,
final VertexIdTranslate idTranslate) throws IOException {
final VertexData<VertexDataType> vertexData = new VertexData<VertexDataType>(numVertices, baseFilename, conv, true);
final DataBlockManager blockManager = new DataBlockManager();
vertexData.setBlockManager(blockManager);
final int CHUNK = 1000000;
return new Iterator<VertexIdValue<VertexDataType>>() {
int i=0, blockId;
Iterator<Integer> curIter;
@Override
public boolean hasNext() {
if (i >= numVertices - 1) return false;
if (curIter == null || !curIter.hasNext()) {
int en = i + CHUNK;
if (en >= numVertices) en = numVertices - 1;
try {
blockId = vertexData.load(i, en);
} catch (IOException e) {
throw new RuntimeException(e);
}
this.curIter = vertexData.currentIterator();
}
return true;
}
@Override
public VertexIdValue next() {
if (hasNext()) {
i = curIter.next();
ChiPointer ptr = vertexData.getVertexValuePtr(i, blockId);
return new VertexIdValue<VertexDataType>(idTranslate.backward(i), blockManager.dereference(ptr, conv));
} else throw new IllegalStateException("No more elements in the iterator!");
}
@Override
public void remove() {
throw new RuntimeException("Remove() not implemented");
}
};
}
private static class SumCallbackInt implements ForeachCallback<Integer> {
long sum = 0;
@Override
public void callback(int vertexId, Integer vertexValue) {
sum += vertexValue;
}
public long getSum() {
return sum;
}
}
/**
* Compute a sum of vertex-values (assumed to be integers)
* @param numVertices number of vertices in the graph (hint: use engine.numVertices())
* @param baseFilename name of the input graph
* @return the sum
* @throws IOException if the vertex data file is not found
*/
public static long sumInt(int numVertices, String baseFilename) throws IOException {
SumCallbackInt callback = new SumCallbackInt();
foreach(numVertices, baseFilename, new IntConverter(), callback);
return callback.getSum();
}
}