diff --git a/lib/optimization/loss_func.cpp b/lib/optimization/loss_func.cpp
index 4d075bb..063171d 100644
--- a/lib/optimization/loss_func.cpp
+++ b/lib/optimization/loss_func.cpp
@@ -31,6 +31,7 @@ gctl::loss_func::loss_func()
 {
     init_ = false;
     eps_ = 1e-16;
+    loss_ = 0.0;
     tnum_ = 0;
     ntype_ = L2;
 }
@@ -117,3 +118,33 @@ double gctl::loss_func::evaluate(const array<double> &x, array<double> &g)
 
     return loss/tnum_;
 }
+
+double gctl::loss_func::evaluate(double inp, int id)
+{
+    double val = (inp - tars_[id])/us_[id];
+
+    if (ntype_ == L1) val = fabs(val);
+    if (ntype_ == L2) val = val*val;
+    
+    loss_ += val;
+
+    return val/tnum_;
+}
+
+double gctl::loss_func::get_loss()
+{
+    double l = loss_;
+    loss_ = 0.0;
+
+    return l;
+}
+
+double gctl::loss_func::gradient(double inp, int id)
+{
+    double val;
+    if (ntype_ == L1 && val >= 0) val = 1.0/(us_[id]*tnum_);
+    if (ntype_ == L1 && val < 0)  val = -1.0/(us_[id]*tnum_);
+    if (ntype_ == L2) val = 2.0*(inp - tars_[id])/(us_[id]*us_[id]*tnum_);
+
+    return val;
+}
\ No newline at end of file
diff --git a/lib/optimization/loss_func.h b/lib/optimization/loss_func.h
index b5c4070..1c1cd54 100644
--- a/lib/optimization/loss_func.h
+++ b/lib/optimization/loss_func.h
@@ -43,11 +43,16 @@ namespace gctl
         void init(const array<double> &tar, norm_type_e n_type, double p = 2.0, double eps = 1e-16);
         void set_uncertainty(double uncer);
         void set_uncertainty(const array<double> &uncer);
+
+        double evaluate(double inp, int id);
         double evaluate(const array<double> &x, array<double> &g);
 
+        double get_loss();
+        double gradient(double inp, int id);
+
     private:
         bool init_;
-        double eps_, p_;
+        double loss_, eps_, p_;
         unsigned int tnum_;
         norm_type_e ntype_;
         array<double> tars_, diff_;