Getting error in yolo_non_max_suppression function

Course Q&A Deep Learning Specialization Convolutional Neural Networks
1

I am getting an error in tf.gather(nms_indices_label,selected_indices)
InvalidArgumentError: indices[0] = 1 is not in [0, 1) [Op:GatherV2]
what can be the possible reason?

2

boxes and scores contain information across all classes. Since we’re performing non-max suppression per label (see here to understand the motivation), the for loop should use boxes and scores for a single label during each pass. Please read the markdown again and look closely at the loop specific variables for invoking non_max_suppression correctly.

As far as tf.gather is concerned, see this as well:

# Append the resulting boxes into the partial result
# Use tf.gather() with 'selected_indices' and `nms_indices_label`

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2 Likes
3

Hi,

I am having the same problem and trying to resolve it for past 24 hours.

You mentioned

the for loop should use boxes and scores for a single label during each pass.

How to select boxes and scores for single label? Since, I am new to TF syntax.

4

They already wrote the logic for you to select one label in each iteration of the loop. Here’s is the first few lines of the template code:

    boxes = tf.cast(boxes, dtype=tf.float32)
    scores = tf.cast(scores, dtype=tf.float32)

    nms_indices = []
    classes_labels = tf.unique(classes)[0] # Get unique classes
    
    for label in classes_labels:
        filtering_mask = classes == label
    
    #### START CODE HERE

So within the loop, the variable label is the current single label value that you are working with and filtering_mask is boolean mask tensor which will be True in the positions that match the current label. Then they give you a pretty big hint in the template code about which TF function to use:

        # Get boxes for this class
        # Use tf.boolean_mask() with 'boxes' and `filtering_mask`
        boxes_label = None
        
        # Get scores for this class
        # Use tf.boolean_mask() with 'scores' and `filtering_mask`
        scores_label = None

Have you read the documentation for TF boolean_mask and gather?

5

Hi, I have the same error
InvalidArgumentError: indices[0] = 1 is not in [0, 1) [Op:GatherV2]

After reading the solution here, I have adjusted the code to reflect the boxes_label and scores_label but will got the same issue. As i can’t put the code here, is there anyway that a mentor could help me please ?
Thanks so much

I have figured it out that I used the gather function wrongly. all good now thank you

1 Like
6

Glad to hear you found the error! Yes, it sounds like you probably reversed the arguments in the “gather” call.