Method apply_discard_plan

src/core/impl/graph/seq_sublinear_memory.cpp:220–361

}

void SeqModifierForSublinearMemory::ModifyActionPlanner::apply_discard_plan() {
    ThinHashSet<Var*> alive_vars;

    // map from original var to duplicated var
    ThinHashMap<Var*, Var*> var_map;

    auto add_alive = [&](Var* var) {
        auto&& ins = alive_vars.insert(var);
        mgb_assert(ins.second);
    };

    auto remove_alive = [&](Var* var) {
        auto nr = alive_vars.erase(var);
        mgb_assert(nr);
    };

    auto check_and_remove = [&](size_t timestamp, Var* var) {
        auto acc = var->visit_discard_tailing_access();
        if (!acc || (acc && acc->opr->time >= timestamp)) {
            mgb_assert(var->owner_opr()->output.size() > 1);
            for (size_t i = 0; i < var->access_rec.size(); ++i) {
                if (var->access_rec[i].time >= timestamp) {
                    mgb_assert(i > 0);
                    auto acc_rec_begin = var->access_rec.data();
                    var->access_rec.resize(i);
                    var->discard_tailing_access = i - 1;
                    mgb_assert(var->access_rec.data() == acc_rec_begin);
                    break;
                }
            }
        }
    };

    auto try_discard = [&](Opr* opr, Var* var) {
        auto acc = var->visit_discard_tailing_access();
        if (acc && acc->opr == opr) {
            remove_alive(var);
            acc[1].opr->inputs_to_recompute.push_back(var);
            auto acc_rec_begin = var->access_rec.data();

            // make this opr as the last reader for original var
            var->access_rec.resize(acc - acc_rec_begin + 1);
            mgb_assert(var->access_rec.data() == acc_rec_begin);
        }
    };

    // recompute a var by inserting new oprs
    auto recompute = [&](Opr* reader, Var* var) {
        mgb_assert(!alive_vars.count(var));

        auto block_begin = var->owner_opr()->block_begin_time,
             block_end = var->owner_opr()->block_end_time;

        thin_function<Var*(Var*)> add_dep;
        add_dep = [&](Var* var) {
            if (alive_vars.count(var))
                return var;
            {