Graph-theory

This maintenance release refactors all of the modules, so they're easier to navigate.
None of the APIs (should) have changed, but should you be missing anything please raise a ticket.

Some may also find that the TSP solver is better and/or faster.

This is a minor maintenance release.

The only changes are:
- bug fix for `solve_tsp` for a rare case where the search runs into a infinite cycle.
- change of name of module `hash` to `hash_methods` to avoid name-space collision with python's built-in `hash`

The version was updated to 2023.1.1 due to the breaking change of the name changes only.

This maintenance release delivers a new algorithm for the detection of phaselines in graphs which reduces the runtime from O(V*E) to O(V+E).

From the docs string:

Detecting phaselines is useful for determining which tasks can be performed in parallel.
Each phase in the phaselines must be completed to assure that the tasks in the next phase can be performed with complete input.

This is in contrast to Topological sort that only generates a queue of tasks, may be fine for a single processor, but has no mechanism for coordination that all inputs for a task have been completed so that multiple processors can work on them.

Here is an example of a DAG with tasks:

u1 u4 u2 u3
\ \ \_______\
csg cs3 append
\ \ \
op1 \ op3
\ \ \
op2 \ cs2
\ \___________\
cs1 join
\ \
map1 map2
\___________\
save

The phaselines would be:

phaselines = {
"u1": 0, "u4": 0, "u2": 0, "u3": 0,
"csg": 1, "cs3": 1, "append": 1,
"op1": 2, "op3": 2,
"op2": 3, "cs2": 3,
"cs1": 4, "join": 4,
"map1": 5, "map2": 5,
"save": 6,
}

From this example it is visible that processing the 4 'uN' (uploads) is the highest degree of concurrency. This can be determined as follows:


d = defaultdict(int)
for _, pl in graph.phaselines():
d[pl] += 1
max_processors = max(d, key=d.get)

Import sped up by importing 3dplot in function call rather than at module top. Credit fiendish
No API changes.

Fix for empty package.

There are no API changes.
Only added support for python 3.7-3.11