Logarithmic arithmetic unit avoiding division as far as predetermined arithmetic precision is guaranteed

摘要

A logarithmic arithmetic unit includes first logarithmic operation part multiplying an exponent part of floating-point data by a prescribed value, a logarithmic table memory outputting a logarithmic value corresponding to bit data expressing a digit higher than a prescribed digit of a fixed-point part of the floating-point data, divisional precision decision part deciding divisional precision on the basis of the exponent part, division part performing division on a dividend obtained by subtracting the bit data from the fixed-point part and a divisor of the bit data and obtaining a result of division of a number of digits set on the basis of the divisional precision, second logarithmic operation part obtaining the logarithmic value of a value obtained by dividing the fixed-point part by the bit data and sum operation part adding outputs from the first and second logarithmic operation parts and the logarithmic table memory to each other.