Coprocessor for Multi-Mode High Precision Nonlinear Activation Function
The deployment of nonlinear activation functions on a chip is suffering from accuracy loss and hardware resource overhead.To address these problems,a multi-mode high-precision coprocessor design framework for nonlinear activation functions is proposed and which is based on the three-split exponential method.In the first stage,the approximation error and the operation workload of nonlinear activation func-tions on different approximation parameters are analyzed to guide the design.In the second stage,a modular hardware framework is designed to deploy several nonlinear activation functions at a low cost by reusing exponential,logarithmic,and sigmoid modules and combining them with floating-point computation units.The prototype of the proposed framework has been implemented on Xilinx Vertix series FPGA.The experi-mental results show that with only 32 additional lookup table entries than the two-split exponential methods,the approximation error of tanh and sigmoid is 65.02％and 69.00％of that using the two-split method,and the fitting range is extended by 60％.Compared with the high-precision piecewise linear approximation method,the design has led to an 82％reduction in approximation error with only 4％of the number of lookup tables in use.
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