src/main/java/org/apache/sysds/runtime/instructions/cp/KahanObject.java

/*
 * 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.sysds.runtime.instructions.cp;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.sysds.common.Types.DataType;
import org.apache.sysds.common.Types.ValueType;


public class KahanObject extends Data 
{

	private static final long serialVersionUID = -5331529073327676437L;

	public double _sum;
	public double _correction;

	public KahanObject(double sum, double cor){
		super(DataType.UNKNOWN, ValueType.UNKNOWN);
		_sum=sum;
		_correction=cor;
	}

	@Override
	public String toString() {
		return "("+_sum+", "+_correction+")";
	}
	
	public static int compare(KahanObject k1, KahanObject k2) {
		if(k1._sum!=k2._sum)
			return Double.compare(k1._sum, k2._sum);
		else 
			return Double.compare(k1._correction, k2._correction);
	}
	
	@Override
	public boolean equals( Object o ) {
		if( !(o instanceof KahanObject) )
			return false;
		KahanObject that = (KahanObject) o;
		return (_sum==that._sum && _correction==that._correction);
	}
	
	@Override
	public int hashCode() {
		throw new RuntimeException("hashCode() should never be called on instances of this class.");
	}
	
	public void read(DataInput in) throws IOException
	{
		_sum=in.readDouble();
		_correction=in.readDouble();
	}
	
	public void write(DataOutput out) throws IOException
	{
		out.writeDouble(_sum);
		out.writeDouble(_correction);
	}
	
	public void set(KahanObject that)
	{
		this._sum=that._sum;
		this._correction=that._correction;
	}
	
	public void set(double s, double c)
	{
		this._sum=s;
		this._correction=c;
	}
	
	public boolean isAllZero()
	{
		return _sum==0 && _correction==0;
	}

	@Override
	public String getDebugName() {
		// TODO Auto-generated method stub
		return null;
	}
}