Commit a73bfdde authored by Robert Ricci's avatar Robert Ricci

New file - documentation of the compile-time options to assign - all 49

of them! The start of an assign cleanup project.
parent 2d610977
This file documents the compile-time options for assign, and known caveats.
Clearly, there are WAY too many of these! Many of these can/should be make into
runtime options, or eliminated altogether.
Debugging/Extra Output
----------------------
VERBOSE Like the name suggests...
DEBUG_TSTEP Print debugging information about temperature steps
STATS Print some stats each step - similar to DEBUG_TSTEP
PCLASS_DEBUG Print out pclasses once they've been determined
GRAPH_DEBUG Print out the switch graph
DUMP_GRAPH Print out the physical graph
ROB_DEBUG Rob's very own debugging output - miscellaneous junk
SCORE_DEBUG Print some messages about certain scoring events
SCORE_DEBUG_LOTS Print virtual and physical nodes/links being scored
SCORE_DEBUG_MORE Print every time we add or subtract the score!
GNUPLOT_OUTPUT Create scores.out, temp.out, delta.out, which are
written every time a transition is accepted, in a form
that gnuplot likes
VIZ_LINK_LABELS When producing graphviz output, label the links
Cooling Schedule Options
------------------------
These four constitute the new, from the literature, cooling schedule:
MELT Start with a melting phase, in which we accept all
transitions, and decide on an initial temperature.
Standard SA stuff.
CHILL Rather than a simple multiplicative decrease in
temperature, uses a function from the literature that
picks the new temperature based on the score change
in the previous temperature stop
NEIGHBOR_LENGTH Base the length of the Markov chains on the approximate
size of the neighborhood structure - simply the number
of vnodes * the number of pclasses
EPSILON_TERMINATE Use a delta function, which is compared against a
constant, epsilon, to determine when we're done, instead
of stopping at a static temperature
PHYS_CHAIN_LEN Make the length of Markov chains (iters. at each
temperature step) dependent on the size of the physical
graph. Not for use with the new cooling schedule
USE_OPTIMAL Exit early if we hit a lower bound we've computed on
the score. Not very maintainable, so not recommended
TIME_TERMINATE Add support for terminating after a given time - bad,
because it doesn't alter the cooling schedule at all
TIME_TARGET Better than TIME_TERMINATE, because it times the melting
run and then does a simple multiplicative decrease
cooling schedule, attempting to hit the target time. Not
very accurate
LOCAL_DERIVATIVE Use the local derivative for EPSILON_TERMINATE - default
is to use the total temperature delta divided by the
total temperature delta
ALLOW_NEGATIVE_DELTA I was having some trouble with EPSILON_TERMINATE -
the average score was getting temporarily worse by
a small amount, causing early termination. If this
variable is not set, the delta function must be
positive for it to trigger termination
LOW_TEMP_STOP Stop at a lower-than-normal temperature. Not for use
with the new cooling schedule
RANDOM_ASSIGNMENT Perform a pseudo-random assignment by exiting as soon
as we get violation-free solution
REALLY_RANDOM_ASSIGNMENT Like RANDOM_ASSIGNMENT, but exits even if there are
violations
FINISH_HILLCLIMB When we would normally terminate, go back to the best
solution and keep going for a while - the idea is to
do a hillclimb from there. Seems like a good idea, but
not well tested
SA Mechanics Options
--------------------
NO_REVERT Normal behavior is to revert to the best solution at
the end of each temperature step. This is somewhat
questionable, so setting this disables it. You should
set REVERT_LAST if this is set!
REVERT_LAST Revert to best solution at the end of the last
temperature step - only needed with NO_REVERT
REVERT_VIOLATIONS Exclusive with NO_REVERT - revert at the end of the
temperature step if the best solution has fewer
violations, but ignore the score
PCLASS_SIZE_BALANCE Weight pclasses by size, instead of giving them equal
weights, so that we're more likely to pick a pclass
that has more members. Of dubious value
FIND_PNODE_SEARCH To find a pnode, assign normally picks the first one
in a pclass - this can cause problems, since this
can result in a pclass getting 'stuck' - all attempts
to map to it fail, because the front pnode has vnodes
assigned to it that prevent mapping. This option causes
a linear search through the pnode members for one that
can be used. Theoretically can increase runtime, but
in practice, does not, and fixes otherwise unmappable
topologies.
LOAD_BALANCE Normally, when multiplexing, assign tends to minimize
the number of pnodes used. This option attempts (with
limited success) to load-balance across the smallest
number of pnodes possible instead. Requires
FIND_PNODE_SEARCH . Intended for ModelNet-type mapping
FIX_LAN_NODES Normally, LAN nodes are annealed just like normal nodes.
This option treats them like fixed nodes - they are only
moved during LAN migration. Not clear if this is a good
idea or not, so it's off by default
AUTO_MIGRATE Performs LAN migration every time a node in the LAN is
re-assigned. This is quite heavyweight, so it increases
runtime quite a bit, and doesn't seem to improve scores
that much. Probably, LAN migration should be made more
lightweight so that this can be turned on without much
computation time penalty
FREE_IMMEDIATELY When assign picks a vnode to re-map, it waits until
after finding a replacement pnode to free the original
mapping. This solves the exact-fit problem in which
nodes being remapped always pick the old mapping again,
since the just-freed pnode is the only one free. This
option reverts to the old behavior, in which the unmap
is done immediately, before picking a new pnode
ALLOW_TRIVIAL_DEFAULT The new behavior for trivial links is that a vlink must
be specially marked in order for assign to be allowed to
satisfy it with a trivial link. This reverts to the old
behavior in which all vlinks are allowed to be mapped to
trivial links by default.
PER_VNODE_TT Normally, assign keeps a 'type table' indicating which
pnodes are potential matches by type - eg., there is
a list of all pc850 nodes. This option builds this table
for each node, instead of for each type. This helps
greatly when there are nodes of the same type, but with
different numbers of interfaces. Also provides some
helpful information up-from about which nodes cannot
be mapped, and could be used to prune down the size of
the search space, since we can ignore nodes that are not
in any node's TT. Unfortunately, breaks vclasses, so
it's off for now
SMART_UNMAP When assign decides that it needs to unmap some existing
mapping, because there are no potential matches for a
vnode, causes it to intelligently unmap a pnode that
could be a match for the current vnode, rather than
picking one a random. Requires PER_VNODE_TT
Scoring Options
---------------
NO_VIOLATIONS Removes special treatment for violations - we still keep
track of them, but they don't affect whether a solution
is accepted. Makes assign behave more like traditional
simulated annealing
FIX_PLINK_ENDPOINTS Allows the 'fixends' option to a plink that specifies
that all vlinks mapped to that plink must have endpoints
on the same pnodes - essentially, an interface can only
talked to one other interface. Useful for ModelNet-type
mapping, and potentially useful for jails, vlinks, and
NSE
FIX_PLINKS_DEFAULT Makes the 'fixends' option the default on all plinks.
Requires FIX_PLINK_ENDPOINTS
PENALIZE_UNUSED_INTERFACES Apply a penalty for every interface not used. Should
favor not wasting interfaces, but its affects on the
overall scoring function are not well-studied
NO_PCLASS_PENALTY Turn off the penalty for using pclasses - intended to
get consistent scores between runs using and not using
pclasses
INTERSWITCH_LENGTH Scale the cost for using interswitch links by the length
of the interswitch path. ie. if a a vlink crosses from
a first switch, through a second, to a third, it incurs
the interswitch penalty two times. Without this option,
assign only assesses the penalty once, no matter how
long the interswitch path
PENALIZE_BANDWIDTH Penalize based on the bandwidth of links that, for
example, cross interswitch links, not just the number
of links. Will need to be in place when we do gigabit,
but not well tested yet
Bugfixes
--------
FIX_SHARED_INTERFACES Fix a bug in which assign was happily re-using
interfaces for more than one vlink, without penalty.
Should be the default
PNODE_SWITCH_LOAD When putting a pnode back into a pclass list, swith the
order in which it is inserted, based on its current
load. Should be the default
PNODE_ALWAYS_FRONT Always put a pnode into the front of its pclass list,
regardless of whether it is being used or not. Only for
debugging PNODE_SWITCH_LOAD - should go away
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