docs: public static void setIdentity( DMatrixRBlock A )
      {
          int minLength = Math.min(A.numRows,A.numCols);
  
          CommonOps_DDRM.fill(A, 0);
  
          int blockLength = A.blockLength;
  
          for( int i = 0; i < minLength; i += blockLength ) {
              int h = Math.min(blockLength,A.numRows-i);
              int w = Math.min(blockLength,A.numCols-i);
  
              int index = i*A.numCols + h*i;
  
              int m = Math.min(h,w);
              for( int k = 0; k < m; k++ ) {
                  A.data[index + k*w + k ] = 1;
              }
          }
      }