Merge branch 'main' into alldifferent_dc

* main: (152 commits)
  v0.8.48
  Don't use AllDifferent with Circuit; might provide an option later
  AllDifferent FWC: refactoring (#54)
  Add 'simple' RosettaCode Sudoku instance
  More changes to factory code
  Update README.md
  Minor
  Some refactoring; unit test for element_2D_var
  Update constraint graph with new domains: fixes and unit tests
  Put back all_different propagator for Circuit constraint
  v0.8.48
  Set status to :unknown if no solutions
  Maintain map of ref -> position withing propagator
  Small change to  propagator
  Changes to error logging; update some benchmarks
  Refactoring (attempt to make branching changes visible to propagation
  Add 100-403 3-Sat Dimacs instances
  v0.8.46
  Fixes for OR, SAT Solver; 2 solvable Dimacs instances
  v0.8.45
  ...

README.md

@@ -16,15 +16,17 @@ Proof of concept. Not suitable for use in production. Significant API changes an
 
 ## Implemented constraints
 
-- `not_equal`
-- `less_or_equal`
+- `equal`, `not_equal`, `less_or_equal`
+- `absolute`
 - `all_different`
-- `sum`
+- `sum`, `modulo`
 - `element`, `element2d`
 - `circuit`
+- `OR`
 
 ## Features
-- views (linear combinations of variables in constraints)  
+- views (linear combinations of variables in constraints)
+- partial support for reified constraints  
 - solving constraint satisfaction (CSP) and constrained optimization (COP) problems
 - parallel search
 - pluggable search strategies
@@ -36,7 +38,7 @@ The package can be installed by adding `fixpoint` to your list of dependencies i
 ```elixir
 def deps do
   [
-    {:fixpoint, "~> 0.8.4"}
+    {:fixpoint, "~> 0.8.28"}
   ]
 end
 ```
@@ -194,7 +196,7 @@ Available options:
 
   [Search strategy](#search). 
 
-- max_space_threads: integer()
+- space_threads: integer()
 
   Defines the number of processes for parallel search. Defaults to 8.
 
@@ -333,7 +335,15 @@ Constraint Optimization Problem - assign facilities to locations so the cost of
 
 https://en.wikipedia.org/wiki/Travelling_salesman_problem
 
+#### [SAT Solver](lib/examples/sat_solver.ex)
+
+#### [Stable Marriage problem](lib/examples/stable_marriage)
+
+https://en.wikipedia.org/wiki/Stable_marriage_problem
+
 #### [`xkcd` comic](livebooks/xkcd_np.livemd)
 
 Two combinatorial problems from https://xkcd.com/287/
 
+#### [Fixpoint models created by Håkan Kjellerstrand](http://hakank.org/elixir/) 
+

data/qap/numbers

@@ -0,0 +1,5 @@
+qap12  - 4776 (opt)
+qap25  - 4752
+qap12a_opt288 - 293
+qap14_opt507 - 515
+qap16_opt34 - 34