Data compression apparatus and data compression method and storage medium

A non-transitory computer-readable storage medium storing a program that causes a computer to execute a process, the process comprising:

• generating dictionary matrix data used for compression based on matrix data for learning;
• generating compressed matrix data that is a result of compression of compression-target matrix data and information on positions at which matrix elements are not zero among respective matrix elements of the compressed matrix data based on the compression-target matrix data and the generated dictionary matrix data;
• comparing a threshold and an index value calculated about a specific value data string that is a data string obtained by coupling specific values specified from element values that are not zero values in each row of the generated compressed matrix data;
• specifying a given constant as respective coefficients when the index value is larger than the threshold;
• calculating reciprocals of respective specific values as the respective coefficients when the index value is equal to or smaller than the threshold;
• and
• outputting, as a compression result, matrix data after operation that is a result of rounding based on a number of places of significant figures of a decimal part in each element that corresponds about products of respective elements of the compressed matrix data and the respective coefficients, regarding the respective elements of the compressed matrix data.

A data compression method executed by a processor included in a data compression apparatus, the data compression method comprising:

• generating dictionary matrix data used for compression based on matrix data for learning;
• generating compressed matrix data that is a result of compression of compression-target matrix data and information on positions at which matrix elements are not zero among respective matrix elements of the compressed matrix data based on the compression-target matrix data and the generated dictionary matrix data;
• comparing a threshold and an index value calculated about a specific value data string that is a data string obtained by coupling specific values specified from element values that are not zero values in each row of the generated compressed matrix data;
• specifying a given constant as respective coefficients when the index value is larger than the threshold;
• calculating reciprocals of respective specific values as the respective coefficients when the index value is equal to or smaller than the threshold;
• and
• outputting, as a compression result, matrix data after operation that is a result of rounding based on a number of places of significant figures of a decimal part in each element that corresponds about products of respective elements of the compressed matrix data and the respective coefficients, regarding the respective elements of the compressed matrix data.

A non-transitory computer-readable storage medium storing a program that causes a computer to execute a process, the process comprising:

• acquiring compressed matrix data obtained based on compression-target matrix data and dictionary matrix data;
• acquiring a specific value based on each piece of row data of the acquired compressed matrix data;
• calculating an index value based on a plurality of the acquired specific values;
• and
• specifying coefficients to correct the compressed matrix data based on the calculated index value and a threshold.