revise inception load behavior for pt <= 1.6

Author: LeoXing1996

mmgen/core/evaluation/metrics.py

@@ -57,6 +57,11 @@ def load_inception(inception_args, metric):
     inceptoin_type = _inception_args.pop('type', None)
 
     if torch.__version__ < '1.6.0':
+        # reset inception_args for FID (Inception for IS do not use
+        # inception_args)
+        if metric == 'FID':
+            _inception_args = dict(normalize_input=False)
+
         mmcv.print_log(
             'Current Pytorch Version not support script module, load '
             'Inception Model from torch model zoo. If you want to use '

tests/test_cores/test_metrics.py

@@ -40,9 +40,12 @@ def test_inception_download():
     with pytest.raises(TypeError):
         load_inception(args_empty, 'FID')
 
-    args_error_path = dict(type='StyleGAN', inception_path='error-path')
-    with pytest.raises(RuntimeError):
-        load_inception(args_error_path, 'FID')
+    # pt lower than this version cannot load Tero's inception and direct use
+    # torch ones, only test this for pt >= 1.6
+    if torch.__version__ >= '1.6.0':
+        args_error_path = dict(type='StyleGAN', inception_path='error-path')
+        with pytest.raises(RuntimeError):
+            load_inception(args_error_path, 'FID')
 
     with pytest.raises(AssertionError):
         load_inception(dict(type='pytorch', normalize_input=False), 'PPL')