Added extra functions to compile model and get loss function

Signed-off-by: Jim Martens <github@2martens.de>

src/twomartens/masterthesis/ssd.py

@@ -21,6 +21,8 @@ Attributes:
     N_CLASSES: number of known classes (without background)
     
 Functions:
+    compile_model(...): compiles an SSD model
+    get_loss_func(...): returns the SSD loss function
     get_model(...): returns correct SSD model and corresponding predictor sizes
     predict(...): runs trained SSD/DropoutSSD on a given data set
     train(...): trains the SSD/DropoutSSD on a given data set
@@ -113,6 +115,35 @@ def get_model(use_dropout: bool,
     return model, predictor_sizes
 
 
+def get_loss_func() -> callable:
+    return keras_ssd_loss.SSDLoss().compute_loss
+
+
+def compile_model(model: tf.keras.models.Model, learning_rate: float, loss_func: callable) -> None:
+    """
+    Compiles an SSD model.
+    
+    Args:
+        model: SSD model
+        learning_rate: the learning rate
+        loss_func: loss function to minimize
+
+    Returns:
+
+    """
+    learning_rate_var = K.variable(learning_rate)
+    
+    # compile the model
+    model.compile(
+        optimizer=tf.train.AdamOptimizer(learning_rate=learning_rate_var,
+                                         beta1=0.9, beta2=0.999),
+        loss=loss_func,
+        metrics=[
+            "categorical_accuracy"
+        ]
+    )
+
+
 def predict(generator: callable,
             steps_per_epoch: int,
             ssd_model: tf.keras.models.Model,
@@ -245,7 +276,6 @@ def train(train_generator: callable,
           iteration: int,
           initial_epoch: int,
           nr_epochs: int,
-          lr: float,
           tensorboard_callback: Optional[tf.keras.callbacks.TensorBoard]) -> tf.keras.callbacks.History:
     """
     Trains the SSD on the given data set using Keras functionality.
@@ -255,29 +285,14 @@ def train(train_generator: callable,
         steps_per_epoch_train: number of batches per training epoch
         val_generator: generator of validation data
         steps_per_epoch_val: number of batches per validation epoch
-        ssd_model: SSD model
+        ssd_model: compiled SSD model
         weights_prefix: prefix for weights directory
         iteration: identifier for current training run
         initial_epoch: the epoch to start training in
         nr_epochs: number of epochs to train
-        lr: initial learning rate
         tensorboard_callback: initialised TensorBoard callback
     """
     
-    # set up variables
-    learning_rate_var = K.variable(lr)
-    ssd_loss = keras_ssd_loss.SSDLoss()
-    
-    # compile the model
-    ssd_model.compile(
-        optimizer=tf.train.AdamOptimizer(learning_rate=learning_rate_var,
-                                         beta1=0.9, beta2=0.999),
-        loss=ssd_loss.compute_loss,
-        metrics=[
-            "categorical_accuracy"
-        ]
-    )
-
     checkpoint_dir = os.path.join(weights_prefix, str(iteration))
     os.makedirs(checkpoint_dir, exist_ok=True)