Class LRSchedule

include/core/optimizer.h:42–85

* @brief Learning rate schedule * * The learning rate schedule class is used for compatibility of string schedule and custom schedule function. * Generally, you don't need to construct this class explictly. */

 * Generally, you don't need to construct this class explictly.
 */
class LRSchedule {
public:
    typedef std::function<float(int, int)> ScheduleFunction;

    std::string type;
    ScheduleFunction schedule_function;

    /** Construct a learning rate schedule */
    LRSchedule(const std::string &_type = "constant") : type(_type) {
        CHECK(type == "linear" || type == "constant") << "Invalid schedule `" << type << "`";
        if (type == "linear")
            schedule_function = linear_schedule;
        if (type == "constant")
            schedule_function = constant_schedule;
    }

    /** Construct a learning rate from custom function */
    LRSchedule(const ScheduleFunction &_schedule_function) :
            type("custom"), schedule_function(_schedule_function) {}

    LRSchedule(const char *_schedule) : LRSchedule(std::string(_schedule)) {}

    /** Call the schedule function */
    float operator ()(int batch_id, int num_batch) {
        return schedule_function(batch_id, num_batch);
    }

    /** Return information about the schedule */
    std::string info() const {
        std::stringstream ss;
        ss << "lr schedule: " << type;
        return ss.str();
    }

    /** Linear decay schedule */
    static float linear_schedule(int batch_id, int num_batch) {
        return std::max(1 - float(batch_id) / num_batch, 1e-4f);
    }

    /** Constant schedule */
    static float constant_schedule(int batch_id, int num_batch) {
        return 1;
    }
};

/**
 * @brief General interface of first-order optimizers