[MATH-628] use only SparseIterator, on RealVectors, that implement SpareRealVectors

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Won't Fix
• Fix Version/s: 3.2
• Assignee: Unassigned
• Reporter: Arne Plöse
• Created: 22/Jul/11 07:07
• Updated: 07/Apr/13 09:15
• Resolved: 13/Mar/13 12:21

Description

the performance suffers badly if one tries to use SparseIterator when there is no sparse backing.
Currently there is only a check for ArrayRealvector, all other is supposed to be a SparseRealvector.
If one creates a new implementation of RealVector ... bang.

here is a performance test case:

package org.apache.commons.math.linear;

import java.util.Iterator;
import org.junit.Test;

/**
 *
 * @author aploese
 */
public class PerformanceTest {

    final static int ITER = 100;
    final static int VECTOR_SIZE = 2048;
    final static double SPARSE_FILL_STATE = 0.8;

    @Test
    public void performanceSparseVectorOpenMap() {
        System.out.println("performanceSparseVectorOpenMap");
        RealVector v = new OpenMapRealVector(VECTOR_SIZE);
        for (int i = 0; i < v.getDimension() * SPARSE_FILL_STATE; i++) {
            v.setEntry(i, i);
        }
        for (int j = 0; j < ITER; j++) {
            long t1 = System.nanoTime();
            double a = 0;
            Iterator<RealVector.Entry> it = v.sparseIterator();
            RealVector.Entry e;
            while (it.hasNext() && (e = it.next()) != null) {
                a += e.getValue();
            }
            long t2 = System.nanoTime();
            for (int i = 0; i < v.getDimension(); i++) {
                a += v.getEntry(i);
            }
            long t3 = System.nanoTime();
            System.out.println(String.format("OpenMap: %d\t%s\t| %s", j, Long.toString(t2 - t1), Long.toString(t3 - t2)));
        }
    }

    @Test
    public void performanceSparseVectorArray() {
        System.out.println("performanceSparseVectorArray");
        RealVector v = new ArrayRealVector(VECTOR_SIZE);
        for (int i = 0; i < v.getDimension() * SPARSE_FILL_STATE; i++) {
            v.setEntry(i, i);
        }
        for (int j = 0; j < ITER; j++) {
            long t1 = System.nanoTime();
            double a = 0;
            Iterator<RealVector.Entry> it = v.sparseIterator();
            RealVector.Entry e;
            while (it.hasNext() && (e = it.next()) != null) {
                a += e.getValue();
            }
            long t2 = System.nanoTime();
            for (int i = 0; i < v.getDimension(); i++) {
                a += v.getEntry(i);
            }
            long t3 = System.nanoTime();
            System.out.println(String.format("Array: %d\t%s\t| %s", j, Long.toString(t2 - t1), Long.toString(t3 - t2)));
        }
    }

Patch will follow.

Issue Links

• is part of: MATH-765 Refactoring the vector and matrix classes