metric.h

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#ifndef XGBOOST_METRIC_H_
#define XGBOOST_METRIC_H_

#include <dmlc/registry.h>
#include <xgboost/base.h>
#include <xgboost/data.h>
#include <xgboost/host_device_vector.h>
#include <xgboost/model.h>

#include <functional>
#include <memory> // shared_ptr
#include <string>
#include <utility>
#include <vector>

namespace xgboost {
struct Context;

class Metric : public Configurable {
 protected
 Context const* ctx_{nullptr};

 public
 virtual void Configure(
 const std::vector<std::pair<std::string, std::string> >&) {}
 void LoadConfig(Json const&) override {}
 void SaveConfig(Json* p_out) const override {
 auto& out = *p_out;
 out["name"] = String(this->Name());
 }

 virtual double Evaluate(HostDeviceVector<bst_float> const& preds,
 std::shared_ptr<DMatrix> p_fmat) = 0;

 virtual const char* Name() const = 0;
 ~Metric() override = default;
 static Metric* Create(const std::string& name, Context const* ctx);
};

struct MetricReg
 : public dmlc::FunctionRegEntryBase<MetricReg,
 std::function<Metric* (const char*)> > {
};

#define XGBOOST_REGISTER_METRIC(UniqueId, Name) \
 ::xgboost::MetricReg& __make_ ## MetricReg ## _ ## UniqueId ## __ = \
 ::dmlc::Registry< ::xgboost::MetricReg>::Get()->__REGISTER__(Name)
} // namespace xgboost
#endif // XGBOOST_METRIC_H_