Squashing functions

[prechelt@ira.uka.de]

> Any interesting squashing function can be stored in a table of negligible size
> (eg 256) with very high accuracy if linear (or higher) interpolation is used.

256 points are not always negligible:
On a fine-grain massively parallel machine such as the MasPar MP-1,
the 256*4 bytes needed to store it can consume a considerable amount of 
the available memory.

Our MP-1216A has 16384 processors with only 16 kB memory each.

Another point: On this machine, I am not sure whether interpolating from
such a table would really be faster than, say, a third order Taylor approximation
of the sigmoid.

  Lutz

Lutz Prechelt   (email: prechelt at ira.uka.de)            | Whenever you 
Institut fuer Programmstrukturen und Datenorganisation  | complicate things,
Universitaet Karlsruhe;  D-7500 Karlsruhe 1;  Germany   | they get
(Voice: ++49/721/608-4068, FAX: ++49/721/694092)        | less simple.