if ( rank == 0 ) {
        for ( int i = 0; i < N; i++ ) {
            for ( int j = 0; j < N; j++ ) {
                XY[0][i * N + j] = i * i + j * j;
            }
        }
    }
    if ( rank == size - 1 ) {
        for ( int i = 0; i < N; i++ ) {
            for ( int j = 0; j < N; j++ ) {
                XY[height - 1][i * N + j] = i * i + j * j + (height - 1) * (height - 1);
            }
        }
    }
    for ( int i = 0; i < height; i++ ) {
        for ( int j = 0; j < N; j++ ) {
            XY[i][j] = i * i + j * j;
            XY[i][j * N] = i * i + j * j;
            XY[i][(N - 1) * N + j] = i * i + j * j + (N - 1) * (N - 1);
            XY[i][j * N + N - 1] = i * i + j * j + (N - 1) * (N - 1);
        }
    }