A controller determines, for each read operation, a mathematical model by using a) a set function of a read threshold voltage set among the plurality of read threshold voltages and b) a set checksum value; determines a polynomial regression model based on the mathematical model; determines a parameter set by using multiple computations between input and output matrices based on the polynomial regression model; and estimates a next read threshold voltage for a next read operation based on the parameter set. The controller computes mathematical operation algorithms to replace a normal multiplication operation, a normal division operation and a normal multiplication followed by division operation.