(1) Elements/BooleanVars should link back to expressions that use them
--> Done
(2) Need to introduce variables in encoding of functions....
--> Done
(3) Some cases can do variable elimination of introduced variables...
(4) Might need to indicate what variables we can query about in
future?
(5) Could simplify output of functions... Maybe several outputs have
same effect...
Work/Passes:
(1) TreeConstruction --- need backwards links...
BooleanVar/ElementVar should be able to query all of its uses. Should
go all the way up...
(2) Naive Encoding Pass --- add an encoding to every Element/Function...
(3) Encoder Pass --- implement encodings into constraint objects...
(4) Test... Make sure the thing works...
Next basic implementation phase:
(1) Extend Naive Encoder Pass to test other encodings
(2) Build more clever function encodings strategies (e.g., equals, add, etc)...
(3) Test
Actual research:
(1) TreeRewriting --- probably should do Equivalent Subexpression
Elimination (Don't have the same expression appear twice, instead
simply link to it again). Possibly good to do in TreeConstruction...
This could be lower priority as it isn't really essential to make
things work. Should also probably be switchable on/off...
--> Done
(2) Advanced TreeRewriting --- can rewrite functions/predicates to
eliminate unused entries or to eliminate effectively identical
outputs... e.g., consider a function f() that can output the values
1,3, 5, 7, and its output is only ever compared to 3... We could
rewrite the values 1, 5, and 7 to be the same value.
(3) Advanced Encoding Strategies
a) encoding alignment --- making binary index encodings over
different sets work together
b) Implement K-Map for function encoding
(4) Implement search framework --- probably simulated annealing over a
population of strategies... search framework should probably be able
to turn on/off nearly any optimization we have...
(5) Implement backend translation strategies....do optimizations and
implement other simplifcation strategies
(6) Convert SATCheck to use Constraint Compiler...not sure about order...
Started...
(7) Profile system....
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To do:
(0) Support for saving/loading problem instances...
(1) Complete satcheck support
(2) Advance tree rewriting... Variable value elimination...
(3) Think about undefined semantics...
(4) Smart encoding...
Variable Graphs....
Split graph into connected components
Encoding ideas:
* Monotonic increasing index
* Matched index (equality)
* Bit exposes
* Single var
* Support arithmetic
* Sparse encoding
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