fix api bugs and different devices calculation bug

[jacktang]

Fix tiny api bugs and different devices calculation bug mentioned at #1352

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Codecov Report

Patch and project coverage have no change.

Comparison is base (c4b1349) 90.13% compared to head (25e0a28) 90.13%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1353   +/-   ##
=======================================
  Coverage   90.13%   90.13%           
=======================================
  Files          30       30           
  Lines        4712     4712           
=======================================
  Hits         4247     4247           
  Misses        465      465           

Flag	Coverage Δ
cpu	90.13% <ø> (ø)
pytest	90.13% <ø> (ø)

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