Calculating transcendental function with piecewise algorithm and its FPGA implementation

Transcendental function is calculated by piecewise approximation algorithm. We analysed relation between approaching precise with segments and limited word length in the example of most commonly used transferring function 'tanh' in neural networks. The method of choosing segments and word length for the needed precise is given. We also implemented calculating 'tanh' based on piecewise algorithm in FPGA. And piecewise approximation algorithm is compared with others fitting hardware, like CORDIC and Look-up table, in the aspect of resource consumed and speed. (authors)