class BlockRealMatrix extends AbstractRealMatrix implements Serializable {

    @Override
    public double getFrobeniusNorm() {
        double sum2 = 0;
        for (int blockIndex = 0; blockIndex < blocks.length; ++blockIndex) {
            for (final double entry : blocks[blockIndex]) {
                sum2 += entry * entry;
            }
        }
        return FastMath.sqrt(sum2);
    }

    public  BlockRealMatrix(final int rows, final int columns);
    public  BlockRealMatrix(final double[][] rawData);
    public  BlockRealMatrix(final int rows, final int columns,
                           final double[][] blockData, final boolean copyArray);

}