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package it.unimi.di.law.vector;

/*		 
 * Copyright (C) 2008-2013 Paolo Boldi, Massimo Santini and Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */

import java.util.Arrays;

// RELEASE-STATUS: DIST

/** A mutable implementation of {@link Vector} optimized for dense vectors. */
public class DenseVector extends Vector {

	static final long serialVersionUID = 2006002L;

	/** An arrays containing vector values. */
	final double[] value;

	/**
	 * Build a vector of given size with zero values.
	 * 
	 * @param size the size.
	 * @param id the id of description of this vector.
	 */
	private DenseVector( final int size, final int id ) {
		super( size, true, id );
		this.value = new double[ size ];
		ell2norm = ell1norm = 0.0;
	}

	/**
	 * Build a vector from an array of values.
	 * 
	 * @param value an array of values.
	 * @param id the id of description of this vector.
	 */
	private DenseVector( final double[] value, final int id ) {
		super( value.length, true, id );
		this.value = value;
		ell2norm = ell1norm = INVALID_NORM;
	}

	/**
	 * Returns an instance of given size with zero values.
	 * 
	 * @param size the size.
	 * @param id the id of description of this vector.
	 * @return a vector.
	 */
	public static DenseVector getInstance( final int size, final int id ) {
		return new DenseVector( size, id );
	}

	/**
	 * Returns an instance from an array of values.
	 * 
	 * @param value an array of values.
	 * @param id the id of description of this vector.
	 * @return a vector.
	 */
	public static DenseVector getInstance( final double[] value, final int id ) {
		return new DenseVector( value, id );
	}

	public void set( final int idx, final double val ) {
		if ( idx < 0 || idx >= size ) throw new IllegalArgumentException( "index out of range" );

		if ( ell1norm != INVALID_NORM ) ell1norm = ell1norm - Math.abs( value[ idx ] ) + Math.abs( val );

		value[ idx ] = val;
		ell2norm = INVALID_NORM;
	}

	public double get( final int idx ) {
		if ( idx < 0 || idx >= size ) throw new IllegalArgumentException( "index out of range" );

		return value[ idx ];
	}

	public void add( final double alpha, final Vector v ) {
		// check size
		if ( size != v.size ) throw new IllegalArgumentException( "vectors with different size" );

		if ( v instanceof DenseVector ) {
			final double[] dvValue = ( (DenseVector)v ).value;

			for ( int i = size; i-- != 0; )
				value[ i ] += dvValue[ i ] * alpha;
		}
		else {
			if ( v instanceof ImmutableSparseVector ) {
				ImmutableSparseVector sv = (ImmutableSparseVector)v;
				final double[] svValue = sv.value;
				final int[] svIndex = sv.index;

				for ( int i = sv.nonZero; i-- != 0; )
					value[ svIndex[ i ] ] += svValue[ i ] * alpha;
			}
			else super.add( alpha, v );
		}

		ell2norm = ell1norm = INVALID_NORM;
	}

	public void scale( final double alpha ) {
		for ( int i = size; i-- != 0; )
			value[ i ] *= alpha;

		// update norm
		if ( ell2norm != INVALID_NORM ) ell2norm *= Math.abs( alpha ); // update norm
		if ( ell1norm != INVALID_NORM ) ell1norm *= Math.abs( alpha );
	}

	public void zero() {
		Arrays.fill( value, 0.0 );
		ell2norm = 0.0; // update norm
	}

	public double dotProduct( final Vector v ) {
		// check size
		if ( size != v.size ) throw new IllegalArgumentException( "vectors with different size" );

		// compute dot product
		if ( v instanceof DenseVector ) {
			final double[] dvValue = ( (DenseVector)v ).value;

			double dot = 0.0;

			double c = 0.0, t, y;
			for ( int i = size; i-- != 0; ) {
				y = ( value[ i ] * dvValue[ i ] ) - c;
				t = dot + y;
				c = ( t - dot ) - y;
				dot = t;

				// dot += value[i] * dvValue[i];
			}

			return dot;
		}
		else if ( v instanceof ImmutableSparseVector ) return v.dotProduct( this );
		else return super.dotProduct( v );
	}

	public double euclideanDistance( final Vector v ) {
		// check size
		if ( size != v.size ) throw new IllegalArgumentException( "vectors with different size" );

		// compute distance
		if ( v instanceof DenseVector ) {
			final double[] dvValue = ( (DenseVector)v ).value;

			double dist = 0.0, temp;

			double c = 0.0, t, y;
			for ( int i = size; i-- != 0; ) {
				temp = value[ i ] - dvValue[ i ];
				y = ( temp * temp ) - c;
				t = dist + y;
				c = ( t - dist ) - y;
				dist = t;

				// temp = value[i] - dvValue[i];
				// dist += temp * temp;
			}

			return Math.sqrt( Math.abs( dist ) );
		}
		else if ( v instanceof ImmutableSparseVector ) return Math.sqrt( Math.abs( dotProduct( this ) + v.dotProduct( v ) - 2 * v.dotProduct( this ) ) );
		else return super.euclideanDistance( v );
	}

	public double ell2Norm() {
		if ( ell2norm == INVALID_NORM ) {
			double tempNorm = 0.0;
			for ( int i = size; i-- != 0; )
				tempNorm += value[ i ] * value[ i ];

			ell2norm = Math.sqrt( Math.abs( tempNorm ) );
		}

		return ell2norm;
	}
	
	@Override
	public double ell1Norm() { 
		if ( ell1norm == INVALID_NORM ) 
		{
			double tempNorm = 0.0;
			for ( int i = size; i-- != 0 ; ) 
				tempNorm += Math.abs( value[ i ] );
			ell1norm = tempNorm;
		}
		
		return ell1norm;
	}

}