Augustin Degomme [Tue, 28 Feb 2023 15:59:29 +0000 (15:59 +0000)]
Merge branch 'udpor-phase3' into 'master'
Phase 2.5 of UDPOR Integration: Add Iterators for Subsets
See merge request simgrid/simgrid!134
Maxwell Pirtle [Tue, 28 Feb 2023 15:36:36 +0000 (16:36 +0100)]
Add src/xbt/.../subsets_tests.cpp to manifest file
Maxwell Pirtle [Tue, 28 Feb 2023 14:52:20 +0000 (15:52 +0100)]
Remove CompatibilityGraph and friends
The CompatibilityGraph and friends that were
added in order to compute maximal sets of events
needlessly complicated the algorithm. A much
better approach was suggested which will be
implemented in the next phase.
While perhaps a rebase could also have been
performed, it would have required quite careful
precision. Since the end goal is the same and
there are better uses of our time, I simply opted
to tag on another commit
Maxwell Pirtle [Tue, 28 Feb 2023 14:31:54 +0000 (15:31 +0100)]
Add tests for LazyKSubsets and LazyPowerset
The LazyKSubsets and LazyPowerset are simply
wrappers around an iterator type which can
enumerate all subsets of a given iteration.
While this won't be used anymore to enumerate
all possible sets of events of the configuration
in the compatibility graph, which will soon be
removed, it will still be used (or a variant
thereof) when computing K-partial alternatives
later on
Maxwell Pirtle [Tue, 28 Feb 2023 10:30:28 +0000 (11:30 +0100)]
Add LazyPowerSet and LazyKSubsets
Two new classes were added that act effectively
as convenience methods around creating subset
iterators. The classes themselves act mostly
like iterators but are instead light-weight
"containers" which can be iterated over. Effectively,
they are contains which "contain" the entire
collection of subsets (of size k respectively) of
some collection without actually storing that collection
in memory.
Maxwell Pirtle [Tue, 28 Feb 2023 10:14:43 +0000 (11:14 +0100)]
Add more comments to subsets_iterator implementation
Maxwell Pirtle [Tue, 28 Feb 2023 09:24:35 +0000 (10:24 +0100)]
Add powerset_iterator to simgrid::xbt
The powerset_iterator, as its name suggests,
is an iterator which traverses over all elements
of the power set of the elements traversed by another
iterator. It makes heavy use of the subsets_iterator
from which it derives its functionality (delegation
rather than inheritance)
Maxwell Pirtle [Tue, 28 Feb 2023 08:37:19 +0000 (09:37 +0100)]
Use boost::iterator_facade for subsets_iterator
The subsets_iterator class is now implemented
in terms of the boost::iterator_facade which simplies
the implementation considerably of the iterator. The
same approach will be used to write the implementation
for powerset_iterator and the history_iterator (the latter
used to traverse the history of a set of events)
Arnaud Giersch [Mon, 27 Feb 2023 16:13:35 +0000 (17:13 +0100)]
Update .mailmap [ci-skip]
Martin Quinson [Mon, 27 Feb 2023 23:17:32 +0000 (00:17 +0100)]
doc: Rework the intro pages
Maxwell Pirtle [Mon, 27 Feb 2023 15:40:48 +0000 (16:40 +0100)]
Remove subsets.cpp file
Since the subsets_iterator is defined using
templates, it needs to be defined solely in
the header file. Thus the cpp file is extraneous
and was removed
Maxwell Pirtle [Mon, 27 Feb 2023 15:37:15 +0000 (16:37 +0100)]
Add "working" (but untested) implementation of iterative subsets
The k-subsets higher-order iterator appears to be
working as expected after fixing a couple of issues
while run under GDB. The next phase is to test this
iterator heavily on a number of different examples
to prove that the iteration works as expected.
Future commits will add two important data structures,
viz. the LazyPowerSet and the LazyKSubsets, both of
which will be used when computing cliques in the
compatibility graph later on
Maxwell Pirtle [Mon, 27 Feb 2023 14:47:04 +0000 (15:47 +0100)]
Add first "implementation" of k-subsets iterator
The higher-order iterator `subsets_iterator`
iterates over all subsets of a given iterator.
Eventually, we'll create the LazyPowerSet and
LazyKSubsets classes which will act as convenience
wrappers around the creation of a k-subset iterator
Maxwell Pirtle [Mon, 27 Feb 2023 12:46:14 +0000 (13:46 +0100)]
Add iterator files to xbt/utils
Martin Quinson [Mon, 27 Feb 2023 13:54:13 +0000 (14:54 +0100)]
Plug a memleak + experience that code out of the MC test for coverage
Martin Quinson [Mon, 27 Feb 2023 10:08:38 +0000 (11:08 +0100)]
cosmetics in docs
Martin Quinson [Mon, 27 Feb 2023 09:16:31 +0000 (10:16 +0100)]
Asynchronous locks and fluid I/O streams were aded at some point
Martin Quinson [Sun, 26 Feb 2023 23:32:48 +0000 (00:32 +0100)]
Add 3 figures to the design goals + minor rewording
Martin Quinson [Sun, 26 Feb 2023 21:45:53 +0000 (22:45 +0100)]
Update release notes
Maxwell Pirtle [Mon, 27 Feb 2023 08:20:49 +0000 (09:20 +0100)]
Fix most of the remaining code warnings
This commit fixes the majority of the code
warnings pointed out by SonarSource. There
are some others that will disappear with other
phases once e.g. the functions in UdporChecker
are actually implemented
Maxwell Pirtle [Mon, 27 Feb 2023 07:57:23 +0000 (08:57 +0100)]
Add default method for constructing full graph
A convenience method was added which allows the
full compatibility graph to be constructed without
needing to specify that each node should be included.
Maxwell Pirtle [Fri, 24 Feb 2023 14:40:39 +0000 (15:40 +0100)]
Add predicate filtering to compatibility graph comp
Computing the compatibility graph should attempt to
disqualify as many events as possible from the configuration
to minimize the size of the resulting compatibility graph.
This is _esepcially_ important because we will enumerate
all cliques of the graph and subsequently all possible
events contains within each node. This means that removing
even one or two nodes could reduce the time spent in
enumeration dramatically.
For now, the UdporChecker can only prune based on
dependency. Perhaps, though, there are more clever
ways to prune based on whether `a` is enabled e.g.
in knowing some properties about the event structure.
This will be investigated later, but is a secondary
concern to getting an implementation of the algorithm
up-and-running.
Maxwell Pirtle [Fri, 24 Feb 2023 13:15:12 +0000 (14:15 +0100)]
Fix most cosmetics and code warnings
Maxwell Pirtle [Fri, 24 Feb 2023 12:52:40 +0000 (13:52 +0100)]
Create a private struct to hold search data
This commits replaces the three separate maps
used to keep track of per-event data in favor
of a single map which maps events to a struct with
three fields
Maxwell Pirtle [Fri, 24 Feb 2023 12:30:36 +0000 (13:30 +0100)]
Add first go at compatibility graph construction
This commit introduces the first (albeit incomplete)
implementation of the function which will convert
a configuration into a comptability graph which can
be iterated over with k-cliques
Maxwell Pirtle [Thu, 23 Feb 2023 15:46:03 +0000 (16:46 +0100)]
Add first steps towards an implementation of ex(C)
Maxwell Pirtle [Thu, 23 Feb 2023 14:14:03 +0000 (15:14 +0100)]
Add CompatibilityGraph and CompatibilityGraphNode
Two important classes were added as part of the
process to support UDPOR. The classes added will be
used to maintain compatibility between "strands" of
the event structure for determining maximal sets of
events
Augustin Degomme [Sun, 26 Feb 2023 21:46:50 +0000 (22:46 +0100)]
[ci skip] add lstdc++ to bigdft flags as well
Augustin Degomme [Sun, 26 Feb 2023 21:04:27 +0000 (21:04 +0000)]
bigdft - attempt at fixing build error with new C++ file in futile
Martin Quinson [Sun, 26 Feb 2023 16:17:19 +0000 (17:17 +0100)]
Allow to control the problem size from the cmd line, and reduce the instance in MC
The previous instance size resulted in a timeout now that the DPOR
reduction is less efficient (because it's less buggy)
Martin Quinson [Sun, 26 Feb 2023 16:16:25 +0000 (17:16 +0100)]
Revalidate a tesh file (result of a merge error)
Martin Quinson [Sun, 26 Feb 2023 15:07:41 +0000 (16:07 +0100)]
Use bool for booleans
Martin Quinson [Sun, 26 Feb 2023 13:15:14 +0000 (14:15 +0100)]
Kill a now useless field
Martin Quinson [Sun, 26 Feb 2023 15:07:08 +0000 (15:07 +0000)]
Merge branch 'master' into 'master'
Fixes on DPOR algorithm for MC SimGrid and sleep sets addition
See merge request simgrid/simgrid!128
Martin Quinson [Sun, 26 Feb 2023 11:30:26 +0000 (12:30 +0100)]
Also detect the disk failures
Martin Quinson [Sun, 26 Feb 2023 11:11:49 +0000 (12:11 +0100)]
Further simplify the way host failures are detected
Do as it's done in links and communications: when the resource is
turned off, simply mark the actions it hosts as FAILED.
That's much simpler than the convoluted existing code, which relied on
the Host::on_state_change signal. Each activity pushed a callback to
check whether it was its host which failed. Gosh, so convoluted...
The current change is not completely applied to CpuTI model, which
seems to have another way to mark the actions as failing. So I
override CpuTI::turn_off() to not mark the actions as failing to avoid
a segfault. It's a bit lame, but CpuTI is too different, I feel lazy.
Martin Quinson [Sat, 25 Feb 2023 17:40:49 +0000 (18:40 +0100)]
Simplify the way Execs detect host failures
Have the ExecImpl install the callback instead of having the s4u::Exec
do so, and then set an internal field of ExecImpl.
Martin Quinson [Fri, 24 Feb 2023 17:51:13 +0000 (18:51 +0100)]
Revert "Include the output of this test in the tesh file, because it's linked from the doc now"
This reverts commit
0c5a9c80339933853647914ea9f716ef4fc8413c.
The output does not seem to be portable :(
Martin Quinson [Fri, 24 Feb 2023 17:39:52 +0000 (18:39 +0100)]
Bummer :(
Arnaud Giersch [Fri, 24 Feb 2023 15:12:19 +0000 (16:12 +0100)]
Clear timeout detectors on finish().
Fixes transient errors seen with s4u-dht-chord-parallel tests.
Arnaud Giersch [Fri, 24 Feb 2023 14:30:34 +0000 (15:30 +0100)]
Fill cmdline_ for each instance of EngimeImpl.
Even if there is only one instance!
Fixes a memory leak occurring when sg_config_init() exits early.
Arnaud Giersch [Fri, 24 Feb 2023 13:48:59 +0000 (14:48 +0100)]
Update sonar-project.properties [ci-skip]
Martin Quinson [Fri, 24 Feb 2023 15:39:28 +0000 (16:39 +0100)]
Two more random hints to contributors (and reindent the existing ones)
Martin Quinson [Fri, 24 Feb 2023 15:32:27 +0000 (16:32 +0100)]
Add some Noteworthy tests to the Contributor's doc
Martin Quinson [Fri, 24 Feb 2023 15:07:22 +0000 (16:07 +0100)]
When the chaos monkey is invoked with nothing to do, it tells a usage message and kills everything
Martin Quinson [Fri, 24 Feb 2023 15:01:41 +0000 (16:01 +0100)]
Include the output of this test in the tesh file, because it's linked from the doc now
Martin Quinson [Fri, 24 Feb 2023 15:00:57 +0000 (16:00 +0100)]
Allow to specify the parameters on the command line, when the test is not run from its favorite directory
Martin Quinson [Fri, 24 Feb 2023 14:58:44 +0000 (14:58 +0000)]
Merge branch 'udpor-phase2' into 'master'
Phase 2 of UDPOR Integration: Add topological sorting of events in a configuration
See merge request simgrid/simgrid!133
mlaurent [Fri, 24 Feb 2023 14:42:51 +0000 (15:42 +0100)]
Merge branch 'master' of https://framagit.org/simgrid/simgrid
mlaurent [Fri, 24 Feb 2023 13:46:46 +0000 (14:46 +0100)]
fix the done marking of multiple times taken transitions
Maxwell Pirtle [Thu, 23 Feb 2023 10:46:10 +0000 (11:46 +0100)]
Add complicated topological sort test
The test added ensures that for each element
in the sequence of events in the topological
sorting:
1. no event in the history of event `i` appears
in the list of events before event `i` (i.e.
events 0, ..., `i - 1`) in the case of the reverse
graph
2. every event in the history of event `i` (except
`e` itself) appears in the list of events before
`i` (i.e. events 0, ..., `i - 1`) in the case of
the event structure ordering
Maxwell Pirtle [Thu, 23 Feb 2023 10:17:27 +0000 (11:17 +0100)]
Add first unit tests for topological sorting
A few unit tests were added to support topological
sorting of events in a configuration. In the future,
a more robust test will be added which ensures that each
newly-discovered event in the reverse order has never
been discovered before
Maxwell Pirtle [Wed, 22 Feb 2023 14:36:18 +0000 (15:36 +0100)]
Add topological sort of configuration events
Topological sorting is an important first step
in determining which groups of events in a
configuration need to be tested together when
looking at all possible subsets of maximal events
of a configuration. The idea is that you first
build a compatability graph (soon to come) whose
elements represent "chains" of the event structure
that are mutually exslcusive and whose edges
describe which chains are mutually compatible
with one another. Then, you look for all possible
cliques within the graph to determine all possible
configurations of these chains. Each of the
major components of this process will be added in
subsequent commits
Martin Quinson [Fri, 24 Feb 2023 00:27:35 +0000 (01:27 +0100)]
Document more changes, and update the Release Notes
Martin Quinson [Fri, 24 Feb 2023 00:19:09 +0000 (01:19 +0100)]
Add a comment on why we need such a callback
Martin Quinson [Thu, 23 Feb 2023 22:59:27 +0000 (23:59 +0100)]
Merge ActivityImpl::post() and ::finish()
Martin Quinson [Thu, 23 Feb 2023 22:16:03 +0000 (23:16 +0100)]
Do not clean twice in Activity::post(), so that even test() can call it
Fred Suter [Thu, 23 Feb 2023 21:14:44 +0000 (16:14 -0500)]
uniformization: call post that calls finish
Martin Quinson [Thu, 23 Feb 2023 21:36:16 +0000 (22:36 +0100)]
Revert "Get ready for more versions of ns3"
This reverts commit
1b8e178fc3f8b3339d25692dfb552f79d349f671.
Also, adds a small comment to avoid this trap in the future.
Martin Quinson [Thu, 23 Feb 2023 21:21:47 +0000 (22:21 +0100)]
Sanitize the handling of timeouts in CommImpl, ExecImpl and IoImpl
There is no need for a timeout detector in ExecImpl and IoImpl, as
wait_for injects a Synchro to that extend on need.
Use a uniq_ptr on the CommImpl timeout detectors, so that the memory
is managed automatically. As it used to be for ExecImpl.
This kills the last occurrence of surf in the code. For real this time.
Arnaud Giersch [Thu, 23 Feb 2023 20:33:28 +0000 (21:33 +0100)]
Fix distcheck.
Martin Quinson [Thu, 23 Feb 2023 20:24:00 +0000 (21:24 +0100)]
Prefer ActivityImpl::post() to ::finish() that should die
Martin Quinson [Wed, 22 Feb 2023 21:58:45 +0000 (22:58 +0100)]
Get ready for more versions of ns3
Arnaud Giersch [Thu, 23 Feb 2023 20:18:18 +0000 (21:18 +0100)]
Comment out unused private fields (fix compilation error).
Arnaud Giersch [Thu, 23 Feb 2023 17:00:25 +0000 (18:00 +0100)]
Merge branch 'simgrid-udpor-integration' into 'master'
Phase 1 of Integration of UDPOR: Adding UDPOR Constructs
See merge request simgrid/simgrid!132
Arnaud Giersch [Thu, 23 Feb 2023 16:14:51 +0000 (17:14 +0100)]
Useless casts to (void*).
Arnaud Giersch [Thu, 23 Feb 2023 15:48:28 +0000 (16:48 +0100)]
Comment is not relevant anymore.
[ci-skip]
Arnaud Giersch [Thu, 23 Feb 2023 14:58:28 +0000 (15:58 +0100)]
Use type aid_t for an actor's PID.
Arnaud Giersch [Thu, 23 Feb 2023 14:53:26 +0000 (15:53 +0100)]
More Sonar issues.
Arnaud Giersch [Thu, 23 Feb 2023 14:37:40 +0000 (15:37 +0100)]
Use normal strings instead of f-strings (Sonar).
Arnaud Giersch [Thu, 23 Feb 2023 13:00:47 +0000 (14:00 +0100)]
Use C++17's std::scoped_lock where appropriate.
Stick to C++14's std::lock_guard in public headers.
Arnaud Giersch [Thu, 23 Feb 2023 12:53:15 +0000 (13:53 +0100)]
Don't access variable ouside of the critical section.
TSan warned about a data race there.
Also use a std::scoped_lock to handle the mutexi (Sonar).
Arnaud Giersch [Tue, 21 Feb 2023 10:59:44 +0000 (11:59 +0100)]
Various cleanups.
Includes:
* prefer simpler overload for channel send/receive
* use direct-initialization for variables
* rename variable and avoid it to be shadowed later
* remove unnecessary casts
mlaurent [Wed, 22 Feb 2023 17:05:37 +0000 (18:05 +0100)]
transitions in the same actor are dependent
Martin Quinson [Wed, 22 Feb 2023 15:55:44 +0000 (16:55 +0100)]
Partially revert
2ad536e710c5936ff8e525e4bbb5e7046f292aac (Simplify the library initialization) to fix a memleak
Martin Quinson [Wed, 22 Feb 2023 15:54:18 +0000 (16:54 +0100)]
Implement the semaphore functions in sthread
mlaurent [Wed, 22 Feb 2023 15:35:29 +0000 (16:35 +0100)]
Merge branch 'master' of https://framagit.org/simgrid/simgrid
mlaurent [Wed, 22 Feb 2023 15:34:19 +0000 (16:34 +0100)]
fix a few test with dpor
Maxwell Pirtle [Wed, 22 Feb 2023 12:40:08 +0000 (13:40 +0100)]
Add tests for adding events to configurations
Maxwell Pirtle [Wed, 22 Feb 2023 12:09:50 +0000 (13:09 +0100)]
Add preliminary tests for Configuration
Martin Quinson [Wed, 22 Feb 2023 11:37:36 +0000 (12:37 +0100)]
protect the dict initialization against multithreading
Maxwell Pirtle [Wed, 22 Feb 2023 10:21:06 +0000 (11:21 +0100)]
Implement adding events to configurations
When adding an event to a configuration, we
assert that the configuration actually contains
all of the dependencies of that event within it;
otherwise, we would violate the property that a
configuration contains all of its dependencies.
Note that we do not assert whether or not the
configuration is actually conflict-free: we leave
that to the correctness of UDPOR and other tests which
will assert UDPOR is doing the right thing. But having
this assertion will certainly help catch bugs with the
UDPOR implementation more quickly (termination would
happen at the moment that the algorithm encounters
a spot where it chose an event incorrectly).
Maxwell Pirtle [Wed, 22 Feb 2023 09:36:33 +0000 (10:36 +0100)]
Add extensive tests for checking valid configurations
An example event structure was given and all
possible subsets of its events were tested for
completeness. Each subset was tested for whether
it was a maximal subset of events (i.e. one for
which no element causes any of the others) and
for whether the set of events qualified for being
a configuration.
An additional observation was made concerning the determination of
whether or not a set of events is maximal. To compute
the maximal events of a given set of events, it suffices
to search the entire history of the events and eliminate
events from the original set as they appear. Note that only
events in the set itself can ever be maximal, as all other
events discovered in the search must have come from one
of these event's dependencies, or one of their dependencies'
dependencies, and so on.
Martin Quinson [Tue, 21 Feb 2023 21:08:45 +0000 (22:08 +0100)]
Cosmetics
- Rename xbt_main.cpp -> xbt_misc.cpp to reflect its content
- Stick to our naming schema (Engine::pimpl -> Engine::pimpl_)
- Don't say the loop iterator is const to then const_cast it
- Kill the leftover xbt::binary_name and xbt::cmdline local vars
Martin Quinson [Tue, 21 Feb 2023 17:21:57 +0000 (18:21 +0100)]
logs: protect finalization against multiple calls
Martin Quinson [Tue, 21 Feb 2023 15:00:06 +0000 (16:00 +0100)]
Let the xbt_log module register its finalizer itself
And kill an internal header file that is now empty
Maxwell Pirtle [Tue, 21 Feb 2023 14:53:53 +0000 (15:53 +0100)]
Add method to check if an EventSet is a config
A method was added that determines whether or not
some set of events (i.e. an `EventSet`) are actually
a valid configuration or not. The question of choosing
valid configurations is up to UDPOR, so while enforcing
that each and every event added to a configuration
be checked to ensure that the configuration remains
as such, it is not strictly necessary. However, it
will help us identify bugs with configurations if
and when they arise.
The key idea behind checking whether a set of events
forms a configuration is to again leverage the power
of History. If while searching through the history
of a set of events you stumble upon an event that is
not part of the original group, then you know that
said group cannot be a configuration since at least
one of the member's dependencies are not part of the
group.
Martin Quinson [Tue, 21 Feb 2023 14:53:00 +0000 (15:53 +0100)]
Kill simgrid::xbt::cmdline and simgrid::xbt::binary_name
Martin Quinson [Mon, 20 Feb 2023 14:46:02 +0000 (15:46 +0100)]
Simplify the library initialization + deprecate 2 XBT functions
Work toward making EngineImpl::initialize() the only entry point of
the library initialization. It's now impossible to initialize xbt
separately of EngineImpl.
It should help reducing the mess in that code, which results from the
many ways of initializing the library. simgrid-mc, unit-tests, smpi
and others each have their own way of initializing everything,
resulting in a spagetthi and fragile code. It's a bit of a waste to
initialize an EngineImpl even when you don't want to actually run a
simulation, but easier code is always better.
This commit also includes another one because I git amended locally by
error, sorry for the mess. The other commit was about the deprecation
of xbt_procname and xbt_getpid that were xbt functions relying on S4U.
Martin Quinson [Mon, 20 Feb 2023 09:00:22 +0000 (10:00 +0100)]
Remove a useless lib constructor (simpler is better)
Martin Quinson [Mon, 20 Feb 2023 08:51:18 +0000 (09:51 +0100)]
Initialize the dict module on need, w/o relying on lib constructors
Maxwell Pirtle [Tue, 21 Feb 2023 13:47:40 +0000 (14:47 +0100)]
Add first batch of tests for History class
Maxwell Pirtle [Tue, 21 Feb 2023 13:08:54 +0000 (14:08 +0100)]
Add first implementations of History class
Maxwell Pirtle [Tue, 21 Feb 2023 12:19:39 +0000 (13:19 +0100)]
Introduce extrinsic equivalence between events
Extrinsic equivalence between two UnfoldingEvents
simply means that we consider to events to be
"the same". This equivalence is used when UDPOR
creates a new event to determine if in fact that
event has already been created. This requires determining
the equivalence between the transitions associated with
those events as well as the dependencies of each of
the events.
Maxwell Pirtle [Tue, 21 Feb 2023 09:35:37 +0000 (10:35 +0100)]
Add tests for the Unfolding object
The Unfolding object currently doesn't have much functionality,
so there is not much that needs to be tested with it. It is
effectively a wrapper around a collection of std::unique_ptr.
Eventually, more functionality may be added when more of the
implementation of UDPOR is added, although its use will still
be quite limited even later
Maxwell Pirtle [Tue, 21 Feb 2023 09:22:42 +0000 (10:22 +0100)]
Add set operator tests for EventSet
This commit introduces test cases for the
common set operators, viz. set union, set
difference, and testing subsets.
Maxwell Pirtle [Mon, 20 Feb 2023 15:31:58 +0000 (16:31 +0100)]
Add tests for EventSet equality
Maxwell Pirtle [Mon, 20 Feb 2023 13:58:51 +0000 (14:58 +0100)]
Add History object skeleton
The History class represents the entire
history of a collection of events "lazily",
i.e. without needing to compute the entire
history if it is not actually needed
Maxwell Pirtle [Mon, 20 Feb 2023 12:54:05 +0000 (13:54 +0100)]
Remove StateManager
The StateManager class was created to wrap
some of the functionality used in tiny_simgrid,
but it turns out that this functionality isn't
actually needed. States are managed entirely
by the UdporChecker/UDPOR in what is
effectively a stack, and it doesn't make sense
for events to talk about states when states
are associated with configurations
Maxwell Pirtle [Mon, 20 Feb 2023 12:38:02 +0000 (13:38 +0100)]
Add first batch of tests for UDPOR
This commit adds tests for the UDPOR constructs
that will be used when UDPOR is finally implemented.
UDPOR will rely heavily on the correctness of
the methods herein and hereafter (in subsequent
commits) tested, so it is important that each function
be tested to the maximum extent possible