TR available: fast exponentiation

[Nici Schraudolph]

Dear colleagues,

the following technical note (5 pages) is available by anonymous ftp; it
may be of interest to those who write their own C/C++ neural network code.

Best regards,
--
    Dr. Nicol N. Schraudolph     Tel: +41-91-970-3877
    IDSIA                        Fax: +41-91-911-9839
    Corso Elvezia 36
    CH-6900 Lugano              http://www.idsia.ch/~nic/
    Switzerland                 http://www.cnl.salk.edu/~schraudo/




Technical Report IDSIA-07-98:

A Fast, Compact Approximation of the Exponential Function
---------------------------------------------------------
Nicol N. Schraudolph

Neural network simulations often spend a large proportion of their time
computing exponential functions.  Since the exponentiation routines of
typical math libraries are rather slow, their replacement with a fast
approximation can greatly reduce the overall computation time.  This
note describes how exponentiation can be approximated by manipulating
the components of a standard (IEEE-754) floating-point representation.
This models the exponential function as well as a lookup table with
linear interpolation, but is significantly faster and more compact.

ftp://ftp.idsia.ch/pub/nic/exp.ps.gz