added F1 measure for evaluation during training

model/config_training_bert.jsonnet

@@ -22,6 +22,8 @@
     },
     "model": {
         "type": "simple_tagger",
+        "calculate_span_f1": true,
+        "label_encoding": "BIOUL",
         "encoder": {
             "type": "lstm",
             "bidirectional": true,
@@ -67,13 +69,14 @@
     "train_data_path": "../data/eng.sdrt.stac/eng.sdrt.stac_train.ner.conllu",
     "validation_data_path": "../data/eng.sdrt.stac/eng.sdrt.stac_dev.ner.conllu",
     "trainer": {
-        "cuda_device": 1,
+        "cuda_device": -1,
         "grad_norm": 5,
         "num_epochs": 4,
-        "num_serialized_models_to_keep": 3,
+        "num_serialized_models_to_keep": 1,
         "optimizer": {
             "type": "bert_adam",
             "lr": 0.001
-        }
+        },
+        "validation_metric": "+f1-measure-overall"
     }
 }
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