Function MGB_IMPL_OPR_GRAD

src/opr/impl/basic_arith.cpp:461–702

#if MGB_ENABLE_GRAD
MGB_IMPL_OPR_GRAD(Elemwise) {
    SymbolVar i[5];
    SymbolVar i0(opr.input(0)), i1, i2, out(opr.output(0)), og{out_grad.at(0)}, result;
    for (size_t t = 0; t < opr.input().size(); ++t)
        i[t] = opr.input()[t];
    if (opr.input().size() >= 2)
        i1 = opr.input(1);
    if (opr.input().size() >= 3)
        i2 = opr.input(2);

    // negate after reduce, for better performance
    bool negate_result = false;
#define RET(_v)    \
    result = (_v); \
    break
#define EL1(_mode, _a)         Elemwise::make({_a}, Mode::_mode)
#define EL2(_mode, _a, _b)     Elemwise::make({_a, _b}, Mode::_mode)
#define EL3(_mode, _a, _b, _c) Elemwise::make({_a, _b, _c}, Mode::_mode)
#define RET_INVALID()          return InvalidGrad::make(opr, wrt_idx)

    using Mode = Elemwise::Mode;

    switch (opr.param().mode) {
        // unary
        case Mode::RELU:
        case Mode::FUSE_ADD_RELU:
            RET(EL2(SWITCH_GT0, out, og));
        case Mode::ABS:
            RET(EL2(ABS_GRAD, i0, og));
        case Mode::ACOS:
            negate_result = true;
            RET(og / EL1(SIN, out));
        case Mode::ASIN:
            RET(og / EL1(COS, out));
        case Mode::ATAN2:
            if (wrt_idx) {
                negate_result = true;
            }
            RET(og * i[!wrt_idx] / (i0 * i0 + i1 * i1));
        case Mode::CEIL:
            return nullptr;
        case Mode::COS:
            negate_result = true;
            RET(EL1(SIN, i0) * og);
        case Mode::EXP:
            RET(og * out);
        case Mode::EXPM1:
            RET(og * EL1(EXP, i0));
        case Mode::FLOOR:
            return nullptr;
        case Mode::LOG:
            RET(og / i0);
        case Mode::LOG1P:
            RET(og / (i0 + 1));
        case Mode::NEGATE:
            negate_result = true;
            RET(og);
        case Mode::SIGMOID: