/*
* 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.ignite.ml.math.impls.storage.vector;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.nio.ByteBuffer;
import java.util.Random;
import org.apache.ignite.ml.math.MurmurHash;
import org.apache.ignite.ml.math.VectorStorage;
import org.apache.ignite.ml.math.exceptions.UnsupportedOperationException;
/**
* {@link VectorStorage} implementation with random values in the vector elements.
*/
public class RandomVectorStorage implements VectorStorage {
/** */
private static final long SCALE = 1L << 32;
/** */
private static final int PRIME = 104047;
/** Random generation seed. */
private int seed;
/** Vector size. */
private int size;
/** Whether fast hash is used, in {@link #get(int)}. */
private boolean fastHash;
/** */
public RandomVectorStorage() {
// No-op.
}
/**
* @param size Size of the storage.
* @param fastHash Whether or not to use fast hashing or Murmur hashing.
*/
public RandomVectorStorage(int size, boolean fastHash) {
assert size > 0;
this.size = size;
this.fastHash = fastHash;
seed = new Random().nextInt();
}
/** {@inheritDoc} */
@Override public int size() {
return size;
}
/** {@inheritDoc} */
@Override public double get(int i) {
if (!fastHash) {
ByteBuffer buf = ByteBuffer.allocate(4);
buf.putInt(i);
buf.flip();
return (MurmurHash.hash64A(buf, seed) & (SCALE - 1)) / (double)SCALE;
}
else
// This isn't a fantastic random number generator, but it is just fine for random projections.
return (((i * PRIME) & 8) * 0.25) - 1;
}
/** {@inheritDoc} */
@Override public void set(int i, double v) {
throw new UnsupportedOperationException("Random vector storage is a read-only storage.");
}
/** {@inheritDoc} */
@Override public void writeExternal(ObjectOutput out) throws IOException {
out.writeInt(size);
out.writeInt(seed);
out.writeBoolean(fastHash);
}
/** {@inheritDoc} */
@Override public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
size = in.readInt();
seed = in.readInt();
fastHash = in.readBoolean();
}
/** {@inheritDoc} */
@Override public boolean isSequentialAccess() {
return true;
}
/** {@inheritDoc} */
@Override public boolean isDense() {
return true;
}
/** {@inheritDoc} */
@Override public boolean isRandomAccess() {
return true;
}
/** {@inheritDoc} */
@Override public boolean isDistributed() {
return false;
}
/** {@inheritDoc} */
@Override public boolean isArrayBased() {
return false;
}
/** {@inheritDoc} */
@Override public int hashCode() {
int res = 1;
res = res * 37 + Boolean.hashCode(fastHash);
res = res * 37 + seed;
res = res * 37 + size;
return res;
}
/** {@inheritDoc} */
@Override public boolean equals(Object o) {
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
RandomVectorStorage that = (RandomVectorStorage)o;
return size == that.size && seed == that.seed && fastHash == that.fastHash;
}
}