title: How to solve "Variable is available in checkpoint, but has an incompatible shape with model variable"?
body: <p>I'm trying to retrain existing pretrained net from object-detection-API. It is ssd_mobilenet_v2. Pre-trained on COCO dataset. I was reproducing steps according to the tutorial pinned to obj-detection-API. </p>
  
  <p>The model starts training anyway, but the % mAP is low. I'm new to CNN's at all, so any help is appreciated.</p>
  
  <p>When I start training, then this warning appears and I can't find a fix.</p>
  
  <p>I'm running it in a google-collaboratory notebook with this command </p>
  
  <pre><code># Training
  !python object_detection/model_main.py \
  --pipeline_config_path=${PIPELINE_CONFIG_PATH} \
  --model_dir=${MODEL_DIR} \
  --num_train_steps=${NUM_TRAIN_STEPS} \
  --sample_1_of_n_eval_examples=$SAMPLE_1_OF_N_EVAL_EXAMPLES \
  --alsologtostderrps
  </code></pre>
  
  <p>this are the warnings I get:</p>
  
  <pre><code>WARNING:root:Variable [FeatureExtractor/MobilenetV2/layer_19_2_Conv2d_2_3x3_s2_512/weights] is     available in checkpoint, but has an incompatible shape with model variable. Checkpoint shape: [[1, 1, 256, 512]], model variable shape: [[3, 3, 256, 512]]. This variable will not be initialized from the checkpoint.
  WARNING:root:Variable [FeatureExtractor/MobilenetV2/layer_19_2_Conv2d_3_3x3_s2_256/weights] is available in checkpoint, but has an incompatible shape with model variable. Checkpoint shape: [[1, 1, 128, 256]], model variable shape: [[3, 3, 128, 256]]. This variable will not be initialized from the checkpoint.
  WARNING:root:Variable [FeatureExtractor/MobilenetV2/layer_19_2_Conv2d_4_3x3_s2_256/weights] is available in checkpoint, but has an incompatible shape with model variable. Checkpoint shape: [[1, 1, 128, 256]], model variable shape: [[3, 3, 128, 256]]. This variable will not be initialized from the checkpoint.
  WARNING:root:Variable [FeatureExtractor/MobilenetV2/layer_19_2_Conv2d_5_3x3_s2_128/weights] is available in checkpoint, but has an incompatible shape with model variable. Checkpoint shape: [[1, 1, 64, 128]], model variable shape: [[3, 3, 64, 128]]. This variable will not be initialized from the checkpoint.
  </code></pre>
  
  <p>after running like 10 minutes it prints out this:</p>
  
  <pre><code>Accumulating evaluation results...
  DONE (t=1.73s).
  Average Precision  (AP) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.000
  Average Precision  (AP) @[ IoU=0.50      | area=   all | maxDets=100 ] = 0.002
  Average Precision  (AP) @[ IoU=0.75      | area=   all | maxDets=100 ] = 0.000
  Average Precision  (AP) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.000
  Average Precision  (AP) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.000
  Average Precision  (AP) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.000
  Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=  1 ] = 0.000
  Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets= 10 ] = 0.006
  Average Recall     (AR) @[ IoU=0.50:0.95 | area=   all | maxDets=100 ] = 0.040
  Average Recall     (AR) @[ IoU=0.50:0.95 | area= small | maxDets=100 ] = 0.002
  Average Recall     (AR) @[ IoU=0.50:0.95 | area=medium | maxDets=100 ] = 0.026
  Average Recall     (AR) @[ IoU=0.50:0.95 | area= large | maxDets=100 ] = 0.050
  </code></pre>
  
  <p>I haven't changed the *.ckpt files just downloaded the original pretrained version of ssd_mobilenet_v2_coco_2018_03_29 and used these and linked them in the .config file.</p>
  
  <p>I'm trying to figure it out for more than a day. 
  Thank you for help.</p>