docs: public static void convert(DMatrixRMaj src , DMatrixRBlock dst ) {
          if( src.numRows != dst.numRows || src.numCols != dst.numCols )
              throw new IllegalArgumentException("Must be the same size.");
  
          for( int i = 0; i < dst.numRows; i += dst.blockLength ) {
              int blockHeight = Math.min( dst.blockLength , dst.numRows - i);
  
              for( int j = 0; j < dst.numCols; j += dst.blockLength ) {
                  int blockWidth = Math.min( dst.blockLength , dst.numCols - j);
  
                  int indexDst = i*dst.numCols + blockHeight*j;
                  int indexSrcRow = i*dst.numCols + j;
  
                  for( int k = 0; k < blockHeight; k++ ) {
                      System.arraycopy(src.data,indexSrcRow,dst.data,indexDst,blockWidth);
                      indexDst += blockWidth;
                      indexSrcRow += dst.numCols;
                  }
              }
          }
      }