diff --git a/constrained_linear_regression/base.py b/constrained_linear_regression/base.py
index 14fa5c9..09b6c9d 100644
--- a/constrained_linear_regression/base.py
+++ b/constrained_linear_regression/base.py
@@ -13,6 +13,8 @@
 from sklearn.neural_network import MLPRegressor
 from sklearn.base import RegressorMixin
 from sklearn.utils import check_X_y
+from sklearn.model_selection import train_test_split
+
 
 class BaseConstrainedLinearRegression(LinearModel, RegressorMixin):
     def __init__(
@@ -26,6 +28,9 @@ def __init__(
         tol=1e-15,
         learning_rate=1.0,
         max_iter=10000,
+        valid_ratio=0,
+        training_losses=[],
+        validation_losses=[],
     ):
         self.fit_intercept = fit_intercept
         self.normalize = normalize
@@ -36,6 +41,9 @@ def __init__(
         self.tol = tol
         self.learning_rate = learning_rate
         self.max_iter = max_iter
+        self.valid_ratio = valid_ratio
+        self.training_losses = training_losses
+        self.validation_losses = validation_losses
 
     def preprocess(self, X, y):
         X, y = check_X_y(
@@ -50,9 +58,12 @@ def preprocess(self, X, y):
             y,
             fit_intercept=self.fit_intercept,
             normalize=self.normalize,
-            copy=self.copy_X
+            copy=self.copy_X,
         )
-        
+
+    def _train_test_split(self, X, y):
+        return train_test_split(X, y, test_size=self.valid_ratio, random_state=42)
+
     def _verify_coef(self, feature_count, coef, value, idx=0):
         if coef is not None:
             coef_ = coef
@@ -62,7 +73,7 @@ def _verify_coef(self, feature_count, coef, value, idx=0):
         else:
             coef_ = np.ones((idx + 1, feature_count)) * value
         return coef_
-    
+
     def _verify_initial_beta(self, feature_count, initial_beta):
         if initial_beta is not None:
             beta = initial_beta
@@ -74,10 +85,21 @@ def _verify_initial_beta(self, feature_count, initial_beta):
     def _set_coef(self, beta):
         self.coef_ = beta
 
+    def _save_mae(self, X, beta, y, loss_scale, X_valid, y_valid):
+        self.training_losses.append(
+            np.sum(np.abs(np.dot(X, beta) - y)) / loss_scale / (1 - self.valid_ratio)
+        )
+        if self.valid_ratio > 0:
+            self.validation_losses.append(
+                np.sum(np.abs(np.dot(X_valid, beta) - y_valid))
+                / loss_scale
+                / self.valid_ratio
+            )
+
     @abc.abstractmethod
     def fit(self, X, y):
         pass
-    
+
 
 class BaseConstrainedMultilayerPerceptron(MLPRegressor, RegressorMixin):
     def __init__(
@@ -106,7 +128,6 @@ def __init__(
         n_iter_no_change=10,
         max_fun=15000,
     ):
-    
         super().__init__(
             hidden_layer_sizes=hidden_layer_sizes,
             activation=activation,
@@ -137,7 +158,7 @@ def __init__(
     @abc.abstractmethod
     def fit(self, X, y):
         pass
-    
+
     def _verify_coef(self, feature_count, coef, value, idx=0):
         if coef is not None:
             coef_ = coef
@@ -146,4 +167,4 @@ def _verify_coef(self, feature_count, coef, value, idx=0):
             ), "Incorrect shape for coef_, the second dimension must match feature_count"
         else:
             coef_ = np.ones((idx + 1, feature_count)) * value
-        return coef_
\ No newline at end of file
+        return coef_
diff --git a/constrained_linear_regression/multi_constrained_linear_regression.py b/constrained_linear_regression/multi_constrained_linear_regression.py
index 60d1228..c794d84 100644
--- a/constrained_linear_regression/multi_constrained_linear_regression.py
+++ b/constrained_linear_regression/multi_constrained_linear_regression.py
@@ -83,6 +83,9 @@ def __init__(
         learning_rate=1.0,
         max_iter=10000,
         penalty_rate=0,
+        valid_ratio=0,
+        training_losses=[],
+        validation_losses=[],
     ):
         super().__init__(
             fit_intercept,
@@ -94,11 +97,27 @@ def __init__(
             tol,
             learning_rate,
             max_iter,
+            valid_ratio,
+            training_losses,
+            validation_losses,
         )
         self.penalty_rate = penalty_rate
 
-    def fit(self, X, y, min_coef=None, max_coef=None, initial_beta=None):
+    def fit(
+        self,
+        X,
+        y,
+        min_coef=None,
+        max_coef=None,
+        initial_beta=None,
+    ):
         X, y, X_offset, y_offset, X_scale = self.preprocess(X, y)
+
+        if self.valid_ratio > 0:
+            # Split the data into training and validation sets
+            X, X_valid, y, y_valid = self._train_test_split(X, y)
+        else:
+            X_valid, y_valid = None, None
         feature_count = X.shape[-1]
         min_coef_ = self._verify_coef(
             feature_count,
@@ -132,8 +151,10 @@ def fit(self, X, y, min_coef=None, max_coef=None, initial_beta=None):
             step += 1
             prev_beta = beta.copy()
 
+            self._save_mae(X, beta, y, loss_scale, X_valid, y_valid)
+            grad = self._calculate_gradient(X, beta, y)
+
             for i, _ in enumerate(beta):
-                grad = self._calculate_gradient(X, beta, y)
                 if self.penalty_rate:
                     progress = step / self.max_iter
                     grad += (