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webmachinelearning / webnn

🧠 Web Neural Network API
https://www.w3.org/TR/webnn/
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Disallow operations on scalar tensors that are no-ops #794

Open reillyeon opened 17 hours ago

reillyeon commented 17 hours ago

There are a number of operators, such as transpose() and reshape() which are no-ops when applied to a scalar tensor. In addition there are operators like gather() which expect indices but a scalar doesn't have indices.

While implementations can work around this (typically by treating a scalar as a single-element 1D tensor) it seems better to simply disallow these cases which add complexity without adding any expressivity.

reillyeon commented 16 hours ago

As an additional data point, both LiteRT and Core ML do not directly support applying their transpose operators to a scalar and implementations based on these frameworks will require workarounds. DirectML only supports this operation because transposition is implemented by adjusting the dimensions and strides of a tensor as it is passed between other nodes, which is a no-op for a scalar tensor.