diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 8389f8a..51217f9 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -54,7 +54,7 @@ jobs:
       - name: Test HUB training
         shell: python
         env:
-         APIKEY: ${{ secrets.ULTRALYTICS_HUB_APIKEY }}
+          APIKEY: ${{ secrets.ULTRALYTICS_HUB_APIKEY }}
         run: |
           import os
           import ultralytics
diff --git a/README.md b/README.md
index 9f721e8..0992175 100644
--- a/README.md
+++ b/README.md
@@ -10,8 +10,8 @@ pip install .  # (dev)
 # pip install ultralytics (production)
 ```
 
-
 ### Usage
+
 ```python
 import ultralytics
 from ultralytics import HUB, YOLO
diff --git a/ultralytics/yolo/__init__.py b/ultralytics/yolo/__init__.py
index b307b3b..85f6f6c 100644
--- a/ultralytics/yolo/__init__.py
+++ b/ultralytics/yolo/__init__.py
@@ -1,3 +1,4 @@
 from .engine.trainer import BaseTrainer
+from .engine.validator import BaseValidator
 
-__all__ = ["BaseTrainer"]  # allow simpler import
+__all__ = ["BaseTrainer", "BaseValidator"]  # allow simpler import
diff --git a/ultralytics/yolo/data/dataset.py b/ultralytics/yolo/data/dataset.py
index 3405b8e..6d95a64 100644
--- a/ultralytics/yolo/data/dataset.py
+++ b/ultralytics/yolo/data/dataset.py
@@ -2,13 +2,10 @@ from itertools import repeat
 from multiprocessing.pool import Pool
 from pathlib import Path
 
-import cv2
-import numpy as np
-import torch
 import torchvision
 from tqdm import tqdm
 
-from ..utils.general import LOGGER, NUM_THREADS
+from ..utils.general import NUM_THREADS
 from .augment import *
 from .base import BaseDataset
 from .utils import BAR_FORMAT, HELP_URL, LOCAL_RANK, get_hash, img2label_paths, verify_image_label
diff --git a/ultralytics/yolo/engine/trainer.py b/ultralytics/yolo/engine/trainer.py
index 17b429f..ac33c8c 100644
--- a/ultralytics/yolo/engine/trainer.py
+++ b/ultralytics/yolo/engine/trainer.py
@@ -28,20 +28,11 @@ DEFAULT_CONFIG = "defaults.yaml"
 
 class BaseTrainer:
 
-    def __init__(
-            self,
-            model: str,
-            data: str,
-            criterion,  # Should we create our own base loss classes? yolo.losses -> v8.losses.clfLoss
-            validator=None,
-            config=CONFIG_PATH_ABS / DEFAULT_CONFIG):
+    def __init__(self, config=CONFIG_PATH_ABS / DEFAULT_CONFIG):
         self.console = LOGGER
-        self.model = model
-        self.data = data
-        self.criterion = criterion  # ComputeLoss object TODO: create yolo.Loss classes
-        self.validator = val  # Dummy validator
+        self.model, self.data, self.train, self.hyps = self._get_config(config)
+        self.validator = None
         self.callbacks = defaultdict(list)
-        self.train, self.hyps = self._get_config(config)
         self.console.info(f"Training config: \n train: \n {self.train} \n hyps: \n {self.hyps}")  # to debug
         # Directories
         self.save_dir = utils.increment_path(Path(self.train.project) / self.train.name, exist_ok=self.train.exist_ok)
@@ -57,7 +48,7 @@ class BaseTrainer:
         self.console.info(f"running on device {self.device}")
         self.scaler = amp.GradScaler(enabled=self.device.type != 'cpu')
 
-        # Model and Dataloaders. TBD: Should we move this inside trainer?
+        # Model and Dataloaders.
         self.trainset, self.testset = self.get_dataset()  # initialize dataset before as nc is needed for model
         self.model = self.get_model()
         self.model = self.model.to(self.device)
@@ -80,9 +71,9 @@ class BaseTrainer:
         try:
             if isinstance(config, (str, Path)):
                 config = OmegaConf.load(config)
-            return config.train, config.hyps
+            return config.model, config.data, config.train, config.hyps
         except KeyError as e:
-            raise Exception("Missing key(s) in config") from e
+            raise KeyError("Missing key(s) in config") from e
 
     def add_callback(self, onevent: str, callback):
         """
@@ -131,10 +122,9 @@ class BaseTrainer:
         self.train_loader = self.get_dataloader(self.trainset, batch_size=self.train.batch_size, rank=rank)
         if rank in {0, -1}:
             print(" Creating testloader rank :", rank)
-            # self.test_loader = self.get_dataloader(self.testset,
-            #                                       batch_size=self.train.batch_size*2,
-            #                                       rank=rank)
-            # print("created testloader :", rank)
+            self.test_loader = self.get_dataloader(self.testset, batch_size=self.train.batch_size * 2, rank=rank)
+            self.validator = self.get_validator()
+            print("created testloader :", rank)
 
     def _do_train(self, rank, world_size):
         if world_size > 1:
@@ -235,11 +225,8 @@ class BaseTrainer:
         """
         pass
 
-    def set_criterion(self, criterion):
-        """
-        :param criterion: yolo.Loss object.
-        """
-        self.criterion = criterion
+    def get_validator(self):
+        pass
 
     def optimizer_step(self):
         self.scaler.unscale_(self.optimizer)  # unscale gradients
@@ -265,6 +252,12 @@ class BaseTrainer:
         if not self.best_fitness or self.best_fitness < self.fitness:
             self.best_fitness = self.fitness
 
+    def build_targets(self, preds, targets):
+        pass
+
+    def criterion(self, preds, targets):
+        pass
+
     def progress_string(self):
         """
         Returns progress string depending on task type.
diff --git a/ultralytics/yolo/engine/validator.py b/ultralytics/yolo/engine/validator.py
index e69de29..7f5e46c 100644
--- a/ultralytics/yolo/engine/validator.py
+++ b/ultralytics/yolo/engine/validator.py
@@ -0,0 +1,105 @@
+import logging
+
+import torch
+from tqdm import tqdm
+
+from ultralytics.yolo.utils import Profile, select_device
+
+
+class BaseValidator:
+    """
+    Base validator class.
+    """
+
+    def __init__(self, dataloader, device='', half=False, pbar=None, logger=None):
+        self.dataloader = dataloader
+        self.half = half
+        self.device = select_device(device, dataloader.batch_size)
+        self.pbar = pbar
+        self.logger = logger or logging.getLogger()
+
+    def __call__(self, trainer=None, model=None):
+        """
+        Supports validation of a pre-trained model if passed or a model being trained
+        if trainer is passed (trainer gets priority).
+        """
+        training = trainer is not None
+        # trainer = trainer or self.trainer_class.get_trainer()
+        assert training or model is not None, "Either trainer or model is needed for validation"
+        if training:
+            model = trainer.model
+            self.half &= self.device.type != 'cpu'
+            model = model.half() if self.half else model
+        else:  # TODO: handle this when detectMultiBackend is supported
+            # model = DetectMultiBacked(model)
+            pass
+
+        model.eval()
+        dt = Profile(), Profile(), Profile(), Profile()
+        loss = 0
+        n_batches = len(self.dataloader)
+        desc = self.set_desc()
+        bar = tqdm(self.dataloader, desc, n_batches, not training, bar_format='{l_bar}{bar:10}{r_bar}{bar:-10b}')
+        self.init_metrics()
+        with torch.cuda.amp.autocast(enabled=self.device.type != 'cpu'):
+            for images, labels in bar:
+                # pre-process
+                with dt[0]:
+                    images, labels = self.preprocess_batch(images, labels)
+
+                # inference
+                with dt[1]:
+                    preds = model(images)
+                    # TODO: remember to add native augmentation support when implementing model, like:
+                    #  preds, train_out = model(im, augment=augment)
+
+                # loss
+                with dt[2]:
+                    if training:
+                        loss += trainer.criterion(preds, labels) / images.shape[0]
+
+                # pre-process predictions
+                with dt[3]:
+                    preds = self.preprocess_preds(preds)
+
+                self.update_metrics(preds, labels)
+
+        stats = self.get_stats()
+        self.check_stats(stats)
+
+        self.print_results()
+
+        # print speeds
+        if not training:
+            t = tuple(x.t / len(self.dataloader.dataset.samples) * 1E3 for x in dt)  # speeds per image
+            # shape = (self.dataloader.batch_size, 3, imgsz, imgsz)
+            self.logger.info(
+                'Speed: %.1fms pre-process, %.1fms inference, %.1fms loss, %.1fms post-process per image at shape ' % t)
+
+        # TODO: implement save json
+
+        return stats
+
+    def preprocess_batch(self, images, labels):
+        return images.to(self.device, non_blocking=True), labels.to(self.device)
+
+    def preprocess_preds(self, preds):
+        return preds
+
+    def init_metrics(self):
+        pass
+
+    def update_metrics(self, preds, targets):
+        pass
+
+    def get_stats(self):
+        pass
+
+    def check_stats(self, stats):
+        pass
+
+    def print_results(self):
+        pass
+
+    def set_desc(self):
+        pass
diff --git a/ultralytics/yolo/utils/__init__.py b/ultralytics/yolo/utils/__init__.py
index 31912d9..304568a 100644
--- a/ultralytics/yolo/utils/__init__.py
+++ b/ultralytics/yolo/utils/__init__.py
@@ -1,4 +1,4 @@
-from .general import WorkingDirectory, check_version, download, increment_path, save_yaml
+from .general import Profile, WorkingDirectory, check_version, download, increment_path, save_yaml
 from .torch_utils import LOCAL_RANK, RANK, WORLD_SIZE, DDP_model, select_device, torch_distributed_zero_first
 
 __all__ = [
@@ -8,6 +8,7 @@ __all__ = [
     "WorkingDirectory",
     "download",
     "check_version",
+    "Profile",
     # torch
     "torch_distributed_zero_first",
     "LOCAL_RANK",
diff --git a/ultralytics/yolo/utils/configs/defaults.yaml b/ultralytics/yolo/utils/configs/defaults.yaml
index ae71597..35b6e02 100644
--- a/ultralytics/yolo/utils/configs/defaults.yaml
+++ b/ultralytics/yolo/utils/configs/defaults.yaml
@@ -1,3 +1,5 @@
+model: null
+data: null
 train:
   epochs: 300
   batch_size: 16
diff --git a/ultralytics/yolo/utils/general.py b/ultralytics/yolo/utils/general.py
index be5ba78..42f78a6 100644
--- a/ultralytics/yolo/utils/general.py
+++ b/ultralytics/yolo/utils/general.py
@@ -5,6 +5,7 @@ import logging
 import os
 import platform
 import subprocess
+import time
 import urllib
 from itertools import repeat
 from multiprocessing.pool import ThreadPool
@@ -208,7 +209,7 @@ def increment_path(path, exist_ok=False, sep='', mkdir=False):
     return path
 
 
-def save_yaml(file='data.yaml', data={}):
+def save_yaml(file='data.yaml', data=None):
     # Single-line safe yaml saving
     with open(file, 'w') as f:
         yaml.safe_dump({k: str(v) if isinstance(v, Path) else v for k, v in data.items()}, f, sort_keys=False)
@@ -278,7 +279,6 @@ class WorkingDirectory(contextlib.ContextDecorator):
 
 def safe_download(file, url, url2=None, min_bytes=1E0, error_msg=''):
     # Attempts to download file from url or url2, checks and removes incomplete downloads < min_bytes
-    from utils.general import LOGGER
 
     file = Path(file)
     assert_msg = f"Downloaded file '{file}' does not exist or size is < min_bytes={min_bytes}"
@@ -301,7 +301,6 @@ def safe_download(file, url, url2=None, min_bytes=1E0, error_msg=''):
 
 def attempt_download(file, repo='ultralytics/yolov5', release='v6.2'):
     # Attempt file download from GitHub release assets if not found locally. release = 'latest', 'v6.2', etc.
-    from utils.general import LOGGER
 
     def github_assets(repository, version='latest'):
         # Return GitHub repo tag and assets (i.e. ['yolov5s.pt', 'yolov5m.pt', ...])
@@ -351,3 +350,23 @@ def attempt_download(file, repo='ultralytics/yolov5', release='v6.2'):
 def get_model(model: str):
     # check for local weights
     pass
+
+
+class Profile(contextlib.ContextDecorator):
+    # YOLOv5 Profile class. Usage: @Profile() decorator or 'with Profile():' context manager
+    def __init__(self, t=0.0):
+        self.t = t
+        self.cuda = torch.cuda.is_available()
+
+    def __enter__(self):
+        self.start = self.time()
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.dt = self.time() - self.start  # delta-time
+        self.t += self.dt  # accumulate dt
+
+    def time(self):
+        if self.cuda:
+            torch.cuda.synchronize()
+        return time.time()
diff --git a/ultralytics/yolo/utils/metrics.py b/ultralytics/yolo/utils/metrics.py
index ea1b3ab..8e910c9 100644
--- a/ultralytics/yolo/utils/metrics.py
+++ b/ultralytics/yolo/utils/metrics.py
@@ -2,6 +2,7 @@
 """
 Model validation metrics
 """
+
 import numpy as np
 
 
diff --git a/ultralytics/yolo/v8/classify/train.py b/ultralytics/yolo/v8/classify/train.py
index 30ac3b4..495d3df 100644
--- a/ultralytics/yolo/v8/classify/train.py
+++ b/ultralytics/yolo/v8/classify/train.py
@@ -4,10 +4,8 @@ from pathlib import Path
 
 import hydra
 import torch
-import torch.hub as hub
 import torchvision
-import torchvision.transforms as T
-from omegaconf import DictConfig, OmegaConf
+from val import ClassificationValidator
 
 from ultralytics.yolo import BaseTrainer, utils, v8
 from ultralytics.yolo.data import build_classification_dataloader
@@ -15,7 +13,7 @@ from ultralytics.yolo.engine.trainer import CONFIG_PATH_ABS, DEFAULT_CONFIG
 
 
 # BaseTrainer python usage
-class Trainer(BaseTrainer):
+class ClassificationTrainer(BaseTrainer):
 
     def get_dataset(self):
         # temporary solution. Replace with new ultralytics.yolo.ClassificationDataset module
@@ -55,13 +53,18 @@ class Trainer(BaseTrainer):
 
         return model
 
+    def get_validator(self):
+        return ClassificationValidator(self.test_loader, self.device, logger=self.console)  # validator
+
+    def criterion(self, preds, targets):
+        return torch.nn.functional.cross_entropy(preds, targets)
+
 
 @hydra.main(version_base=None, config_path=CONFIG_PATH_ABS, config_name=str(DEFAULT_CONFIG).split(".")[0])
 def train(cfg):
-    model = "squeezenet1_0"
-    dataset = "imagenette160"  # or yolo.ClassificationDataset("mnist")
-    criterion = torch.nn.CrossEntropyLoss()  # yolo.Loss object
-    trainer = Trainer(model, dataset, criterion, config=cfg)
+    cfg.model = cfg.model or "squeezenet1_0"
+    cfg.data = cfg.data or "imagenette160"  # or yolo.ClassificationDataset("mnist")
+    trainer = ClassificationTrainer(cfg)
     trainer.run()
 
 
diff --git a/ultralytics/yolo/v8/classify/val.py b/ultralytics/yolo/v8/classify/val.py
new file mode 100644
index 0000000..4657ffc
--- /dev/null
+++ b/ultralytics/yolo/v8/classify/val.py
@@ -0,0 +1,18 @@
+import torch
+
+from ultralytics import yolo
+
+
+class ClassificationValidator(yolo.BaseValidator):
+
+    def init_metrics(self):
+        self.correct = torch.tensor([])
+
+    def update_metrics(self, preds, targets):
+        correct_in_batch = (targets[:, None] == preds).float()
+        self.correct = torch.cat((self.correct, correct_in_batch))
+
+    def get_stats(self):
+        acc = torch.stack((self.correct[:, 0], self.correct.max(1).values), dim=1)  # (top1, top5) accuracy
+        top1, top5 = acc.mean(0).tolist()
+        return {"top1": top1, "top5": top5, "fitness": top5}