void af_test4() {
    af::array S = af::randu(4, 4, c32);  //4*4的complex float数组
    af_print(S);

    af::array S11 = S(af::seq(2), af::seq(2)); // 左上分块
    af_print(S11);

    af::array S12 = S(af::seq(2), af::seq(2, af::end)); // 右上分块
    af_print(S12);

    af::array S21 = S(af::seq(2, af::end), af::seq(2)); // 左下分块
    af_print(S21);

    af::array S22 = S(af::seq(2, af::end), af::seq(2, af::end)); // 右下分块
    af_print(S22);
}

There are three constructors for af::seq.

• af::seq(N): Defines a range between 0 and N-1
• af::seq(begin, end) Defines a range between begin and end inclusive
• af::seq(begin, end, step) defines a range between begin and end striding by step values

https://arrayfire.org/docs/indexing.htm