Tensorboard path generalisation (#804)

* Allow experiment versions to be overridden by passing a string value.
Allow experiment names to be empty, in which case no per-experiment subdirectory will be created and checkpoints will be saved in the directory given by the save_dir parameter.

* Document tensorboard api changes

* Review comment fixes plus fixed test failure for minimum requirements build

* More format fixes from review

pytorch_lightning/loggers/tensorboard.py

@@ -29,9 +29,12 @@ class TensorBoardLogger(LightningLoggerBase):
 
     Args:
         save_dir (str): Save directory
-        name (str): Experiment name. Defaults to "default".
-        version (int): Experiment version. If version is not specified the logger inspects the save
-        directory for existing versions, then automatically assigns the next available version.
+        name (str): Experiment name. Defaults to "default".  If it is the empty string then no per-experiment
+            subdirectory is used.
+        version (int|str): Experiment version. If version is not specified the logger inspects the save
+            directory for existing versions, then automatically assigns the next available version.
+            If it is a string then it is used as the run-specific subdirectory name,
+            otherwise version_${version} is used.
         \**kwargs  (dict): Other arguments are passed directly to the :class:`SummaryWriter` constructor.
 
     """
@@ -47,6 +50,30 @@ def __init__(self, save_dir, name="default", version=None, **kwargs):
         self.tags = {}
         self.kwargs = kwargs
 
+    @property
+    def root_dir(self):
+        """
+        Parent directory for all tensorboard checkpoint subdirectories.
+        If the experiment name parameter is None or the empty string, no experiment subdirectory is used
+        and checkpoint will be saved in save_dir/version_dir
+        """
+        if self.name is None or len(self.name) == 0:
+            return self.save_dir
+        else:
+            return os.path.join(self.save_dir, self.name)
+
+    @property
+    def log_dir(self):
+        """
+        The directory for this run's tensorboard checkpoint.  By default, it is named 'version_${self.version}'
+        but it can be overridden by passing a string value for the constructor's version parameter
+        instead of None or an int
+        """
+        # create a pseudo standard path ala test-tube
+        version = self.version if isinstance(self.version, str) else f"version_{self.version}"
+        log_dir = os.path.join(self.root_dir, version)
+        return log_dir
+
     @property
     def experiment(self):
         r"""
@@ -61,10 +88,8 @@ def experiment(self):
         if self._experiment is not None:
             return self._experiment
 
-        root_dir = os.path.join(self.save_dir, self.name)
-        os.makedirs(root_dir, exist_ok=True)
-        log_dir = os.path.join(root_dir, "version_" + str(self.version))
-        self._experiment = SummaryWriter(log_dir=log_dir, **self.kwargs)
+        os.makedirs(self.root_dir, exist_ok=True)
+        self._experiment = SummaryWriter(log_dir=self.log_dir, **self.kwargs)
         return self._experiment
 
     @rank_zero_only
@@ -108,8 +133,7 @@ def save(self):
             # you are using PT version (<v1.2) which does not have implemented flush
             self.experiment._get_file_writer().flush()
 
-        # create a preudo standard path ala test-tube
-        dir_path = os.path.join(self.save_dir, self.name, 'version_%s' % self.version)
+        dir_path = self.log_dir
         if not os.path.isdir(dir_path):
             dir_path = self.save_dir
 

tests/test_logging.py

@@ -294,6 +294,19 @@ def test_tensorboard_manual_versioning(tmpdir):
     assert logger.version == 1
 
 
+def test_tensorboard_named_version(tmpdir):
+    """Verify that manual versioning works for string versions, e.g. '2020-02-05-162402' """
+
+    tmpdir.mkdir("tb_versioning")
+    expected_version = "2020-02-05-162402"
+
+    logger = TensorBoardLogger(save_dir=tmpdir, name="tb_versioning", version=expected_version)
+    logger.log_hyperparams({"a": 1, "b": 2})  # Force data to be written
+
+    assert logger.version == expected_version
+    # Could also test existence of the directory but this fails in the "minimum requirements" test setup
+
+
 @pytest.mark.parametrize("step_idx", [10, None])
 def test_tensorboard_log_metrics(tmpdir, step_idx):
     logger = TensorBoardLogger(tmpdir)