Weight data compression method, weight data decompression method, weight data compression device, and weight data decompression device

A weight data compression device comprising:

• a compressor that compresses ternary weight data used in a neural network,
• wherein the compressor:
• generates a 4-bit data string by dividing the ternary weight data into data items each having 4 bits, the ternary weight data being a data string of data items each having any one of three 2-bit values, the 4-bit data string being a data string of 4-bit data items each expressed as any one of nine 4-bit values;
• and
• generates first compressed data including a first flag value string and a first non-zero value string by generating the first flag value string and the first non-zero value string, the first flag value string being generated by assigning one of 0 and 1 as a first flag value of a 1-bit flag to a 4-bit data item 0000 and assigning an other of 0 and 1 as a second flag value of the 1-bit flag to a 4-bit data item other than 0000 among the 4-bit data items in the 4-bit data string, the first non-zero value string being generated by converting the 4-bit data item other than 0000 into a 3-bit data item having any one of eight 3-bit values.