[Tensorflow][Object detection] ValueError when try to train with --num_clones=2
You don't mention which type of model you are training - if like me you were using the default model from the TensorFlow Object Detection API example (Faster-RCNN-Inception-V2) then num_clones should equal the batch_size. I was using a GPU however, but when I went from one clone to two, I saw a similar error and setting batch_size: 2 in the training config file was the solution.
I wanted to train on multiple CPU so i run this command

C:\Users\solution\Desktop\Tensorflow\research>python
  object_detection/train.py --logtostderr
  --pipeline_config_path=C:\Users\solution\Desktop\Tensorflow\myFolder\power_drink.config --train_dir=C:\Users\solution\Desktop\Tensorflow\research\object_detection\train
  --num_clones=2 --clone_on_cpu=True

and i got the following error

Traceback (most recent call last):   File "object_detection/train.py",
  line 169, in 
      tf.app.run()   File "C:\Users\solution\AppData\Local\Programs\Python\Python35\lib\site-packages\tensorflow\python\platform\app.py",
  line 124, in run
      _sys.exit(main(argv))   File "object_detection/train.py", line 165, in main
      worker_job_name, is_chief, FLAGS.train_dir)   File "C:\Users\solution\Desktop\Tensorflow\research\object_detection\trainer.py",
  line 246, in train
      clones = model_deploy.create_clones(deploy_config, model_fn, [input_queue])   File
  "C:\Users\solution\Desktop\Tensorflow\research\slim\deployment\model_deploy.py",
  line 193, in create_clones
      outputs = model_fn(*args, **kwargs)   File "C:\Users\solution\Desktop\Tensorflow\research\object_detection\trainer.py",
  line 158, in _create_losses
      train_config.merge_multiple_label_boxes) ValueError: not enough values to unpack (expected 7, got 0) 

If i set num_clones to 1 or omitted it, it works normally.
I also tries setting --ps_tasks=1 which doesn't help
any advice would be appreciated