== Why _apt_ is always going to be faster than _yum_

One of the things that people report (to put it politely) when they
switch between a Debian-derived distribution and Fedora is that _apt_ is
faster than _yum_. This is indeed the case, and it is always going to be
the case, because _yum_ is simply doing far more work than _apt_ is.

(Whether or not the speed difference matters in practice is another
debate. It doesn't bother me, but then I use fairly fast and beefy
machines.)

As I understand it, the different amount of work is ultimately due
to a basic difference in how each system approaches dependencies. In
Debian, the approach to dependencies is entirely package based;
package A declares that it requires packages B, C, and D. In RPMs, the
dependencies are mostly on *things*, like files and libraries; while you
can make your RPM explicitly depend on packages, you generally don't.

The end result is that there are a lot more dependencies running around
an RPM-based system than there are around a Debian one, and many of
them are indirect dependencies (you don't depend on a package directly,
you depend on something provided by a package). Thus, doing things on
an RPM-based system means checking a lot more dependencies, in bigger
indexes, and generally taking more steps in resolving each dependency to
a package. In short, more work that deals with more data, which means
slower.

(The RPM based system has bigger dependency indexes because it has to
include files and libraries and so on in them, not just packages.)

As a side note, I suspect that it doesn't help that _yum_ has larger
indexes and downloads them a lot more often than _apt_ does.