limit "t" and correct prev non blank so that task=search works

[mikel-zhobro]

Now task=search should work as intended.

[albertz]

I don't understand. Why is this needed? Esp in search, this should have no effect.

[mikel-zhobro]

prev:output_ doesn't guarantee non_blank during search. Both are sparse, but it messes up the embedding that happens in slow_rnn.

I get something like this:

TensorFlow exception: indices[0] = 1056 is not in [0, 1056)
         [[node output/rec/slow_rnn/masked/input_embed/linear/embedding_lookup (defined at /Users/mikel/setups/rt4/returnn/returnn/tf/layers/basic.py:1468) ]]

Errors may have originated from an input operation.
Input Source operations connected to node output/rec/slow_rnn/masked/input_embed/linear/embedding_lookup:
 output/rec/slow_rnn/masked/input_embed/linear/py_print_1/Identity (defined at /Users/mikel/setups/rt4/returnn/returnn/tf/util/basic.py:6245)

[albertz]

Hm, this is strange. Haven't we used it always like this in the other configs as well? Why did the problem never occur? Also, I have used exactly this config, and it did not occur for me. How can that be?

What TensorFlow version do you use?

Also, maybe we should fix MaskedComputationLayer instead? This can only happen for frames for slow_rnn which will actually not be used (due to the masking). It does not really matter what we calculate in those masked-out frames. We could simply fix the input for the masked-out frames.

But first I want to understand better why this happens now and not before, and not for me.

[mikel-zhobro]

Haven't we used it always like this in the other configs as well?

It looks the same in other configs, I don't get it either.

What TensorFlow version do you use?

2.4.1

This can only happen for frames for slow_rnn which will actually not be used (due to the masking)

Exactly.

But first I want to understand better why this happens now and not before, and not for me.

Here are my logs.