NNAPI can use both GPUs and DSP/NPU.
For example, if you quantize your models to 8bits, DSP/NPU will be used otherwise GPU will be the main computing unit.
The quantization is optional in the above example.
More benchmarks and information could be found here.

  
      
      Medium – 12 Nov 20
  
  
    

PyTorch Mobile Now Supports Android NNAPI 75

NNAPI allows Android apps to run computationally intensive neural networks on the parts of the chips that power mobile phones.

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