org.apache.mahout.math.hadoop.stochasticsvd.DenseBlockWritable Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package org.apache.mahout.math.hadoop.stochasticsvd;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Arrays;
import org.apache.hadoop.io.Writable;
/**
* Ad-hoc substitution for {@link org.apache.mahout.math.MatrixWritable}.
* Perhaps more useful for situations with mostly dense data (such as Q-blocks)
* but reduces GC by reusing the same block memory between loads and writes.
*
*
* in case of Q blocks, it doesn't even matter if they this data is dense cause
* we need to unpack it into dense for fast access in computations anyway and
* even if it is not so dense the block compressor in sequence files will take
* care of it for the serialized size.
*
*/
public class DenseBlockWritable implements Writable {
private double[][] block;
public void setBlock(double[][] block) {
this.block = block;
}
public double[][] getBlock() {
return block;
}
@Override
public void readFields(DataInput in) throws IOException {
int m = in.readInt();
int n = in.readInt();
if (block == null) {
block = new double[m][0];
} else if (block.length != m) {
block = Arrays.copyOf(block, m);
}
for (int i = 0; i < m; i++) {
if (block[i] == null || block[i].length != n) {
block[i] = new double[n];
}
for (int j = 0; j < n; j++) {
block[i][j] = in.readDouble();
}
}
}
@Override
public void write(DataOutput out) throws IOException {
int m = block.length;
int n = block.length == 0 ? 0 : block[0].length;
out.writeInt(m);
out.writeInt(n);
for (double[] aBlock : block) {
for (int j = 0; j < n; j++) {
out.writeDouble(aBlock[j]);
}
}
}
}