Fix MAX_STEPS = 0 error by add suggestion and exit (#1195)

## What this patch does to fix the issue.
Change the minimum no. of `MAX_STEPS` to 1.

## Link to any relevant issues or pull requests.
#1194

blueoil/cmd/train.py

@@ -16,6 +16,7 @@
 from datetime import datetime
 import math
 import os
+import sys
 
 import tensorflow as tf
 from tensorflow.core.util.event_pb2 import SessionLog
@@ -192,8 +193,14 @@ def start_training(config, profile_step):
     # Calculate max steps. The priority of config.MAX_EPOCHS is higher than config.MAX_STEPS.
     if "MAX_EPOCHS" in config:
         max_steps = int(train_dataset.num_per_epoch / config.BATCH_SIZE * config.MAX_EPOCHS)
+        if max_steps < 1:
+            print("The max_steps is less than 1, consider reduce BATCH_SIZE. exit.", file=sys.stderr)
+            sys.exit(1)
     else:
         max_steps = config.MAX_STEPS
+        if max_steps < 1:
+            print("The max_steps is less than 1, consider set MAX_STEPS greater than 0. exit.", file=sys.stderr)
+            sys.exit(1)
 
     progbar = Progbar(max_steps)
     if rank == 0: