MXNet NLP GloVe model causes error "Native resource has been released already"

[tadayosi]

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Description

When I try to use the MXNet zoo model ai.djl.mxnet/glove/0.0.2/glove, it throws the following error and I cannot use it for NLP word embedding:

Exception in thread "main" java.lang.IllegalStateException: Native resource has been released already.
	at ai.djl.util.NativeResource.getHandle(NativeResource.java:64)
	at ai.djl.mxnet.engine.MxNDArray.getShape(MxNDArray.java:148)
	at ai.djl.ndarray.NDList.toString(NDList.java:538)
	at java.base/java.lang.String.valueOf(String.java:4465)
	at java.base/java.io.PrintStream.println(PrintStream.java:1187)
	at word_embedding.main(word_embedding.java:31)

Expected Behavior

It should not throw the error.

Error Message

See the description.

How to Reproduce?

I use this simple code:

public class WordEmbedding {
    public static void main(String... args) throws Exception {
        var criteria = Criteria.builder()
                .optApplication(Application.NLP.WORD_EMBEDDING)
                .setTypes(String.class, NDList.class)
                .optArtifactId("glove")
                .optProgress(new ProgressBar())
                .build();
        var model = criteria.loadModel();

        var input = "test";
        try (var predictor = model.newPredictor()) {
            var ndlist = predictor.predict(input);
            ndlist.detach();
            System.out.println(ndlist);
        }
    }

Steps to reproduce

Run the above sample code.

What have you tried to solve it?

I searched the Issues and found this: https://github.com/deepjavalibrary/djl/issues/1064#issuecomment-871054042.

So according to @frankfliu, a Translator should not return NDList in general and otherwise the error is expected. However, it is this ai.djl.mxnet/glove/0.0.2/glove model's translator that returns NDList.

NLP.WORD_EMBEDDING :: ai.djl.mxnet/glove/0.0.2/glove {"dimensions":"50"}
  - Args: {dimensions=50, unknownToken=<unk>, translatorFactory=ai.djl.mxnet.zoo.nlp.embedding.GloveWordEmbeddingTranslatorFactory, blockFactory=ai.djl.mxnet.zoo.nlp.embedding.GloveWordEmbeddingBlockFactory}
  - Factory: ai.djl.mxnet.zoo.nlp.embedding.GloveWordEmbeddingTranslatorFactory
  - In/Out: java.lang.String => ai.djl.ndarray.NDList

That leads me to an impression that it's not something that can be fixed at my end but rather a bug in the model / translator.

Thanks.