Summary:
Mostly cosmetic except for a change in [solve_eq] to try harder at
normalization (improves unit tests!). Add more comments and do minor
renamings.
Reviewed By: skcho
Differential Revision: D23243629
fbshipit-source-id: 55bdaf8a8
Summary:
This does a bunch of things at once (sorry):
- Refactor atom/term normalisation so that terms that are really just
atoms become atoms.
- Use this to not bother adding special cases in the functions exported
in the .mli: `and_less_than`, `and_equal_binop`, `prune_binop`, etc.
all had special cases to avoid introducing terms that could be atoms.
That's not great because the same smarts wasn't applied to terms that
would only become atom-like after some normalisation, and led to weird
and duplicated code. Now it's much cleaner: just add the most
straighforward fact and normalise!
- Fix a bug: adding a new equality `x = linear` should *not* be done
using `Normalizer.merge_var_linarith` as this is an internal function
that assumes that `x` is the right representative in `x - linear`.
Instead, for abitrary equations of that form, `solve_eq` should be used.
- When `normalize_linear_eqs` discovers new linear equalities, normalize
again. Add fuel there too to avoid spending too much time doing that.
It could be that we don't need/want fuel there but then we'd need to
think very hard about why there's no infinite recursion possible and
that seems harder.
Reviewed By: skcho
Differential Revision: D23241282
fbshipit-source-id: e5b8c4759
Summary:
This allows further normalisation now that terms contain linear
expressions in normal form.
Reviewed By: skcho
Differential Revision: D23241499
fbshipit-source-id: f8e4e759c
Summary:
Linear arithmetic is able to simplify more atoms, eg `x+y <= x+y`
becomes `True` by normalising to "lhs - rhs <= 0". This does the first
step of normalisation, but to get True in this example we also need to
substitute inside atoms according to the linear equalities, which is the
next diff (for now we only substitute variables inside atoms for other
variables or for constants).
Reviewed By: skcho
Differential Revision: D23241457
fbshipit-source-id: 0da0b545c
Summary:
Make term simplification a bit more structured and separate the
"simplification" phase from the "evaluating constant expressions" phase.
Also implement the latter for all possible terms.
Reviewed By: skcho
Differential Revision: D23241334
fbshipit-source-id: 2964aa477
Summary: Not much to see here, extracted to make further changes more readable.
Reviewed By: da319
Differential Revision: D23241335
fbshipit-source-id: 81181f23a
Summary:
Since this is where almost all of the reasoning is concentrated, let's
make sure we use it at every opportunity!
Reviewed By: skcho
Differential Revision: D23194224
fbshipit-source-id: fedb2811e
Summary:
Reset the state before each test so that adding tests doesn't affect
other tests by shifting the ids of their anonymous variables.
Reviewed By: skcho
Differential Revision: D23194171
fbshipit-source-id: 7b717f160
Summary:
Instead of alternating between a normal form and a tree structure,
always keep a normal form. Except the normal form is not always fully
normalized. Overall, it's a bit faster than the previous iteration,
while being more precise! In particular, linear arithmetic aims at being
much more complete.
Reviewed By: skcho
Differential Revision: D23134209
fbshipit-source-id: 5f9ec6ece
Summary:
At the end of analysing a procedure we call `simplify
~keep:vars_live_in_pre_post`. Any variable not in
`vars_live_in_pre_post` is not mentioned anywhere else in the state and
therefore is not going to contribute constraints in callers of the
procedure (in other words: they're dead). We want to also forget
arithmetic facts about these variables as this is a good opportunity to
make the path condition smaller, sometimes by a lot!
The main issue is that dead variables may be useful intermediate terms
in the formula, eg trying to keep only facts about `x` in `y = x + 1 &&
y = 0` is going to lose a lot of precision. But, if a variable not in
`keep` is only mentioned in a simple atom `z = 42` atom, for example,
it's safe to forget about it, eg it's safe to remember only `x=0` in
`x=0 && z=42` (if only `x` is live).
In other words, we can get rid of all atoms containing variables not
transitively involved in other atoms that eventually involve live
variables. A graph problem! This is guaranteed not to forget anything
important and can still trim a lot of atoms in certain situations.
Reviewed By: skcho
Differential Revision: D22921313
fbshipit-source-id: 6d5db7cbe
Summary:
Perhaps a bit overkill to introduce all this extra complexity but it
makes the unit tests much more readable. In fact, this uncovered a bug
in the dead variable elimination!
Reviewed By: dulmarod
Differential Revision: D22925548
fbshipit-source-id: d1f411683
Summary:
Do not always add parens around sub-terms, and add more parens around
terms in atoms and normal forms when they can be confused with the atom
or normal form structure.
Reviewed By: skcho
Differential Revision: D22925549
fbshipit-source-id: 8646e96a5
Summary: These will change to more interesting outputs in the next diff.
Reviewed By: dulmarod
Differential Revision: D22921349
fbshipit-source-id: c58c6240a
Summary:
Add unit tests to pulse in order to write tests for the arithmetic
solver, because it is a pain to write programs to do that end to end.
Reviewed By: ezgicicek
Differential Revision: D22864607
fbshipit-source-id: 0a20a3593
Jules Villard