From octave-maintainers-request at bevo dot che dot wisc dot edu Mon Jan 13 21:22:00 2003
Subject: Re: overloaded functions
From: Paul Kienzle <pkienzle at users dot sourceforge dot net>
To: Andy Adler <adler at site dot uottawa dot ca>
Cc: octave-maintainers at bevo dot che dot wisc dot edu
Date: Mon, 13 Jan 2003 22:20:25 -0500

Andy Adler wrote:

>[dispatch is] a really useful function, Paul.
>
>Does it add any significant overhead?
>
A lookup in a very small hash table, an extra feval call, so yes it is
a little bit expensive.

octave:10> tic; for i=1:1000, sin(1); end; toc
ans = 0.047647
octave:11> tic; for i=1:1000, cos(1); end; toc
ans = 0.037207

If you wanted to, you could keep the actual function values in the
structure, and so avoid the extra feval.  Since the number of types
we are likely to dispatch against is small, an array is perhaps a
better representation then a map.  You could be using type-ids rather
than strings to compare types.  This might be enough to make the
presense of dispatch unmeasurable.

Paul Kienzle
pkienzle at users dot sf dot net