Computer storage device and classification method thereof

A storage device comprising:

• a computing in-memory unit storing a plurality of first weights;
• a storage unit storing a plurality of second weights, the plurality of second weights are corresponding to the plurality of first weights, wherein a bit length of the second weight is larger than a bit length of the first weight;
• a controller coupled to the computing in-memory unit and the storage unit;
• and
• a classification accelerator coupled to the computing in-memory unit, the storage unit and the controller,
• wherein
• the computing in-memory unit calculates a plurality of first computation results of the plurality of first weights with an input data;
• the classification accelerator compares the first computation results with a threshold value to obtain a comparison result;
• based on the comparison result, the controller reads out a first portion of the plurality of second weights corresponding to a plurality of candidate classes from the storage unit;
• the classification accelerator calculates a plurality of second computation results of the first portion of the plurality of second weights with the input data;
• and
• based on the second computation results, the classification accelerator selects a plurality of target candidate classes with top one or several highest product values from the candidate classes.