allow test_single from backward

Author: donglaiw

connectomics/config/defaults.py

@@ -482,7 +482,7 @@
 _C.INFERENCE.IS_ABSOLUTE_PATH = None
 _C.INFERENCE.DO_CHUNK_TITLE = None
 
-# Do inference one-by-on (load a volume when needed).
+# Do inference one-by-one (load a volume when needed).
 _C.INFERENCE.DO_SINGLY = False
 _C.INFERENCE.DO_SINGLY_START_INDEX = 0
 _C.INFERENCE.DO_SINGLY_STEP = 1

connectomics/engine/trainer.py

@@ -310,8 +310,11 @@ def test_singly(self):
             else:
                 # same file location
                 output_name = [x+'_result.h5' for x in img_name]
-
-        for i in range(self.cfg.INFERENCE.DO_SINGLY_START_INDEX, num_file, self.cfg.INFERENCE.DO_SINGLY_STEP):
+        
+        ran = range(self.cfg.INFERENCE.DO_SINGLY_START_INDEX, num_file, abs(self.cfg.INFERENCE.DO_SINGLY_STEP))
+        if self.cfg.INFERENCE.DO_SINGLY_STEP < 0:
+            ran = ran[::-1]
+        for i in ran:
             self.test_filename = output_name[i]
             if not os.path.exists(self.test_filename):
                 if dir_name is not None: