fix(wandb): allow use of sweeps

CHANGELOG.md

@@ -64,6 +64,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Added a missing call to the `on_before_zero_grad` model hook ([#1493](https://github.com/PyTorchLightning/pytorch-lightning/pull/1493)). 
 
+- Allow use of sweeps with WandbLogger ([#1512](https://github.com/PyTorchLightning/pytorch-lightning/pull/1512))
+
 - Fixed a bug that caused the `callbacks` Trainer argument to reference a global variable ([#1534](https://github.com/PyTorchLightning/pytorch-lightning/pull/1534)).
 
 - Fixed a bug that set all boolean CLI arguments from Trainer.add_argparse_args always to True ([#1570](https://github.com/PyTorchLightning/pytorch-lightning/issues/1570))

pytorch_lightning/loggers/wandb.py

@@ -114,7 +114,7 @@ def watch(self, model: nn.Module, log: str = 'gradients', log_freq: int = 100):
     @rank_zero_only
     def log_hyperparams(self, params: Union[Dict[str, Any], Namespace]) -> None:
         params = self._convert_params(params)
-        self.experiment.config.update(params)
+        self.experiment.config.update(params, allow_val_change=True)
 
     @rank_zero_only
     def log_metrics(self, metrics: Dict[str, float], step: Optional[int] = None) -> None:

tests/loggers/test_wandb.py

@@ -23,7 +23,7 @@ def test_wandb_logger(wandb):
     wandb.init().log.assert_called_once_with({'global_step': 3, 'acc': 1.0})
 
     logger.log_hyperparams({'test': None})
-    wandb.init().config.update.assert_called_once_with({'test': None})
+    wandb.init().config.update.assert_called_once_with({'test': None}, allow_val_change=True)
 
     logger.watch('model', 'log', 10)
     wandb.init().watch.assert_called_once_with('model', log='log', log_freq=10)