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oj! Algorithms - ojAlgo - is Open Source Java code that has to do with mathematics, linear algebra and optimisation.

There is a newer version: 55.0.1

package org.ojalgo.matrix.transformation;

import org.ojalgo.function.aggregator.Aggregator;
import org.ojalgo.function.constant.PrimitiveMath;
import org.ojalgo.matrix.store.MatrixStore;
import org.ojalgo.matrix.store.PhysicalStore;
import org.ojalgo.scalar.PrimitiveScalar;
import org.ojalgo.structure.Access2D.RowView;
import org.ojalgo.type.NumberDefinition;

final class HouseholderRow> extends RowView implements HouseholderReference {

    private int myFirst = 0;
    private final MatrixStore myStore;
    private transient Householder myWorker = null;

    public HouseholderRow(final MatrixStore store) {

        super(store);

        myStore = store;
    }

    @Override
    public long count() {
        return myStore.countColumns();
    }

    @Override
    public double doubleValue(final long index) {
        if (index > myFirst) {
            return myStore.doubleValue(this.row(), index);
        }
        if (index == myFirst) {
            return PrimitiveMath.ONE;
        } else {
            return PrimitiveMath.ZERO;
        }
    }

    public int first() {
        return myFirst;
    }

    @Override
    public N get(final long index) {
        if (index > myFirst) {
            return myStore.get(this.row(), index);
        }
        if (index == myFirst) {
            return myStore.physical().scalar().one().get();
        } else {
            return myStore.physical().scalar().zero().get();
        }
    }

    @SuppressWarnings("unchecked")
    public > P getWorker(final PhysicalStore.Factory factory) {
        if (myWorker == null) {
            myWorker = factory.makeHouseholder((int) this.count());
        }
        return (P) myWorker;
    }

    public boolean isZero() {
        double largest = NumberDefinition.doubleValue(myStore.aggregateRow(this.row(), myFirst + 1L, Aggregator.LARGEST));
        return PrimitiveScalar.isSmall(PrimitiveMath.ONE, largest);
    }

    public void point(final long row, final long col) {
        this.goToRow(row);
        myFirst = (int) col;
    }

}