@Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof OpenMapRealVector)) {
            return false;
        }
        OpenMapRealVector other = (OpenMapRealVector) obj;
        if (virtualSize != other.virtualSize) {
            return false;
        }
        if (Double.doubleToLongBits(epsilon) !=
            Double.doubleToLongBits(other.epsilon)) {
            return false;
        }
        Iterator iter = entries.iterator();
        while (iter.hasNext()) {
            iter.advance();
            double test = other.getEntry(iter.key());
            if (Double.doubleToLongBits(test) != Double.doubleToLongBits(iter.value())) {
                return false;
            }
        }
        iter = other.getEntries().iterator();
        while (iter.hasNext()) {
            iter.advance();
            double test = iter.value();
            if (Double.doubleToLongBits(test) != Double.doubleToLongBits(getEntry(iter.key()))) {
                return false;
            }
        }
        return true;
    }