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<P><FONT SIZE="5">5.7 Efficiency Notes</FONT><BR>
<P>The following notes are worth keeping in mind when
using FunnelWeb.
<P><BLOCKQUOTE><B>Memory:</B> When
FunnelWeb processes an input file, it reads the entire input
file, and all the included files into memory. (Note: If a
file is included n times, FunnelWeb keeps n copies in
memory). This organization does not pose a constraint on
machines with large memories, but could present a problem on
the smaller machines such as the PC.</BLOCKQUOTE>
<P><BLOCKQUOTE><B>Speed:</B> FunnelWeb is not a
slow program. However, it is not particularly fast either.
If the speed at which FunnelWeb runs is important to you,
then the thing to keep in mind is that FunnelWeb has been
optimized to deal efficiently with large slabs of text.
FunnelWeb treats input files as a sequence of text slabs and
special sequences (e.g. <SAMP>@+</SAMP>) and whenever it hits
a special sequence, it has to stop and think. Thus, while a
ten megabyte text slab would be manipulated as a single
token, in a few milliseconds, a similar ten megabyte chunk
filled with special sequences would take a lot longer. If
FunnelWeb is running slowly, look to see if the input
contains a high density of special sequences. This can
sometimes happen if FunnelWeb is being used as a backend
macro processor and its input is being generated
automatically by some other program.</BLOCKQUOTE>
<P><BLOCKQUOTE><B>Macro
expansion:</B> When tangling
(expanding macros), FunnelWeb never expands a macro
expression into memory; it always writes it to the product
file as it goes. This is a powerful fact, because it means
that you can write macros containing an unlimited amount of
text, and pass such macros as parameters to other macros
without becoming concerned about overflowing some kind of
buffer memory. In short, FunnelWeb does not impose any
limits on the size of macro bodies or their expansions.</BLOCKQUOTE>
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