Iterating over a symbolic `tf.Tensor` is not allowed: AutoGraph did convert this function

[Zihan Mei]

Issue type

Bug

Have you reproduced the bug with TensorFlow Nightly?

No

Source

source

TensorFlow version

tf 2.9

Custom code

Yes

OS platform and distribution

Linux Ubuntu 22.04

Mobile device

No response

Python version

No response

Bazel version

No response

GCC/compiler version

No response

CUDA/cuDNN version

No response

GPU model and memory

No response

Current behavior?

I have a function as below. I have N = tf.shape(y_true)[0] where y_ture is <tf.Tensor 'y_true:0' shape=(None, 8, 6) dtype=float32>. I later iterate over N as for i in tf.range(N), but get an error.

def transform_targets_for_output(y_true, grid_size, anchor_idxs):
    # y_true: (N, boxes, (x1, y1, x2, y2, class, best_anchor))
    print('y-true',y_true)
    N = tf.shape(y_true)[0]
    print('%%%',N)

    # y_true_out: (N, grid, grid, anchors, [x1, y1, x2, y2, obj, class])
    y_true_out = tf.zeros(
        (N, grid_size, grid_size, tf.shape(anchor_idxs)[0], 6))

    anchor_idxs = tf.cast(anchor_idxs, tf.int32)

    indexes = tf.TensorArray(tf.int32, 1, dynamic_size=True)
    updates = tf.TensorArray(tf.float32, 1, dynamic_size=True)
    idx = 0
    for i in tf.range(N):
        for j in tf.range(tf.shape(y_true)[1]):
            if tf.equal(y_true[i][j][2], 0):
                continue
            anchor_eq = tf.equal(
                anchor_idxs, tf.cast(y_true[i][j][5], tf.int32))

            if tf.reduce_any(anchor_eq):
                box = y_true[i][j][0:4]
                box_xy = (y_true[i][j][0:2] + y_true[i][j][2:4]) / 2

                anchor_idx = tf.cast(tf.where(anchor_eq), tf.int32)
                grid_xy = tf.cast(box_xy // (1/grid_size), tf.int32)

                # grid[y][x][anchor] = (tx, ty, bw, bh, obj, class)
                indexes = indexes.write(
                    idx, [i, grid_xy[1], grid_xy[0], anchor_idx[0][0]])
                updates = updates.write(
                    idx, [box[0], box[1], box[2], box[3], 1, y_true[i][j][4]])
                idx += 1

    # tf.print(indexes.stack())
    # tf.print(updates.stack())

    return tf.tensor_scatter_nd_update(
        y_true_out, indexes.stack(), updates.stack())

But I get error like this:

raise e.with_traceback(filtered_tb) from None
  File "/home/shakey/yolov3-tf2/yolov3_tf2/dataset.py", line 42, in transform_targets_for_output
    for i in tf.range(N):
tensorflow.python.framework.errors_impl.OperatorNotAllowedInGraphError: Iterating over a symbolic `tf.Tensor` is not allowed: AutoGraph did convert this function. This might indicate you are trying to use an unsupported feature.

How can I solve that?

Standalone code to reproduce the issue

nothing.

Relevant log output

No response