footprint as it runs. All the credit for this one goes to Tim!

pnode's types were a subset of another's.

top and ptop files, you can put
subnode_of:nodename
Any vnode that is a subnode must be mapped to a pnode that is a a
subnode of the pnode the vnode's parent is mapped to. Read that a few
times slowly, I swear it makes sense.

really working this time.

I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite
I will not check things in without running the testsuite

Split the function that determines if a vnode can be mapped to a given pnode
out of find_pnode, so that I can spread it out and make it more comprehensible.
In doing so, fixed a bug in which static types were not getting handled
correctly - a static type would only be found if no vnodes with dynamic types
were allocated to the pnode.

Fixed a bug in which, on allocation of a dynamic ptype, nodes where being
removed from their static type lists in the type_table.

Fixed a bug when there is a combination of fixed and un-fixed vnodes in the top
file.

I have more on the way, but this seemed like a good checkpoint.

was sooo wrong you wonder how it worked in the first place... Took
me days to find this one!

Also added a new switch, '-o', that lets assign try out solutions
that over-load a pnode. This helps a lot with topologies where the
optimal solution is a best-fit onto multiplexed pnodes.

The end result is that Mike's snake maps much better - it used to get
an essentially random mapping, but now it gets something acceptible.

After building the set of pclasses normally, we make another pass
through the vnodes. The goal to create a pclass for each individual
node. We disable the node's 'own' pclass to begin with. Then, the
_first_ time it gets a vnode mapped to it, we remove it from the
'regular' pclass it belongs to, and enable it's own pclass. Then, if
it goes empty, we put it back in its regular pclass and disable it's
own.

The point of this is to replace -p for use with multiplexed nodes.
Instead of disabling pclasses altogheter, which has serious
performance implications, we can instead be smart about which pnodes
remain equivalent (because nothing's been mapped to them), and which
are now different. The result is that on my test topoloy, the time to
get a good mapping has gone from over 3 minutes to about 6 seconds.

This feature is enabled with the -d option, and the -P option is
pretty much mandatory when using it, since it greatly exacerbates the
problem of cruft in the ptop file.

This satisfies #14 from the todo file:
14.  do dynamic pclasses

Also bumped up the minimum neighborhood size from 500 to 1000. In some
tests I was doing, this resulted in better solutions.

LAN nodes are no longer treated specially. Instead, I've introduced
the idea of 'static' types (old-style types retroactively become
'dynamic' types). While a pnode can only satisfy one dynamic type at a
time, it can always satisfy its static types (assuming it has enough
capacity left.) Static types are flagged by prepending them with a '*'
in the ptop file. So, for example, you may give switches the
'*lan:10000' type so that they can satisfy virtual LAN nodes. Of
course, other pnodes can have this type too, so that we can get
'trivial LANs'.

Actually, removing special treatment for LANs cleans up a lot of code.
However, it may have some negative impacts on solutions, since we're
not as smart about where to place LAN nodes as we used to be (they get
annealed along with everything else, and not migrated.) I haven't seen
any evidence of this yet, however.

This leaves us with a single type of special pnode, a switch.

Also added a new bit of syntax in ptop files - when '*' is given as a
the maxiumum load for a type, the node is allowed to take on an
infinite (well, actually, just a really big number of) vnodes of that
type.

ptopgen was modified to always report switches as being capable of
hosting LANs, and assign_wrapper now understands direct links to LANs,
which is what we get when the LAN is hosted directly on a switch.

Fixed a bug in scoring direct links, in which the penatly was being
added once when a direct link was mapped, but subtracted only once
when it was freed.

Added a '-T' option for doing simple self-testing. When adding a node
to the solution, assign records the score, adds the node, removes it
again, and checks to make sure that the resulting score is the same as
the original score. The usefulness of this feature in debugging
scoring problems cannot be understated...

some independant functionality off into new files, and reduce its
use of globals, which can be very confusing to follow.

I didn't get as far as I had hoped, but it's a good start.

using the new assign, and captures Leigh's linkdelays work.

time to debug a delayed LAN problem.

In addition to assign, assign_wrapper and ptopgen have been modified
to output the new formats used by assign.

make-vclass A 0.5 pc600 pc850

in the top file.  And then have nodes of type A.  Assign will try to put
them all as either pc600 or pc850.

Still need to write all the pre-assign stuff.

pclasses.  This involved removing the heuristics, which, for the most
part, were not worth the cycles they consumed, and scaled badly.

This check-in consists of 7 modifications to assign.

1. Equivalence Classes

Defined an equivalence relation on the physical nodes and applied it
to the physical topology to get the resulting quotient topology (abuse
of terminology).  So instead of searching among all possible physical
nodes to make a map, assign only searches among all possible
equivalence classes of nodes.  This tremendously reduces the search
space.  At the time of this writing it reduces the physical topology
from 252 nodes to 13 nodes.  The equivalence classes are generated
automatically from the ptop file.

2. Scoring based on equivalence classes.

Each equivalence class used comes with a significant cost.  This
strongly encourages assign to use equivalence machines when possible.
The result is that an experiment that does not otherwise specify will
almost definitely get machines of the same type.  If this needs to be
reduced in the future it is the SCORE_PCLASS constant.

3. Heuristics

Added a bunch of heuristics for choosing which equivalence class to
use.  This was less successful than I hoped.  A good solution is now
found in record time but it still continues searching.  When OPTIMAL
is turned on these heuristics help a lot.  When off they make little
difference.  I may turn this into a compile time option in the future
since the heuristics do take non-trivial CPU cycles.

4. Fixed the very-very-big-and-evil disconnected-switches bug.

Assign wasn't cleaning up after itself in certain cases.  Disconnected
graphs are now merely a minor, easily ignored, bump rather than the
towering cliffs they use to be.

5. Fixed the not-yet-noticed not-enough-nodes bug.

Found a bug that probably has never come up before because we have
checks that avoid those circumstances.

6. Modified constants.

I was tired of waiting so long for results so, I lowered CYCLES and
reduced the constant for naccepts (Mac, you probably want to add that
inconspicuous number to your configurable constants; look for
"naccepts =").  The results is roughly a speedup of 2.  It works great
currently but we may want to change these numbers up again if we get
problems with features and desires.

7. General clean up.

Associated with the other changes was a lot of restructuring and some
cleanup.  Specifically to the assign loop and scoring code.