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Implement raw constraints for Bit

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This commit is contained in:
Sean Bowe 2016-01-24 01:42:29 -07:00
parent 506ef75e3c
commit ececc2b60b
2 changed files with 77 additions and 37 deletions
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78
src/bit.rs
View File

@ -214,14 +214,68 @@ fn resolve(a: &Var, b: &Var, op: Op) -> Var {
vals.set_output(0, op.val(a, b));
}, |i, o, cs| {
cs.push(match op {
And => Constraint::And(i[0].index(), i[1].index(), o[0].index()),
Nand => Constraint::Nand(i[0].index(), i[1].index(), o[0].index()),
Xor => Constraint::Xor(i[0].index(), i[1].index(), o[0].index()),
Xnor => Constraint::Xnor(i[0].index(), i[1].index(), o[0].index()),
Nor => Constraint::Nor(i[0].index(), i[1].index(), o[0].index()),
Or => Constraint::Or(i[0].index(), i[1].index(), o[0].index()),
MaterialNonimplication => Constraint::MaterialNonimplication(i[0].index(), i[1].index(), o[0].index()),
MaterialImplication => Constraint::MaterialImplication(i[0].index(), i[1].index(), o[0].index())
// a * b = c
And => Constraint(vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![(FieldT::one(), o[0].clone())]
),
// a * b = 1 - c
Nand => Constraint(vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![(FieldT::one(), Var::one()),
(-FieldT::one(), o[0].clone())
]
),
// 2a * b = a + b - c
Xor => Constraint(vec![(FieldT::from(2), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![(FieldT::one(), i[0].clone()),
(FieldT::one(), i[1].clone()),
(-FieldT::one(), o[0].clone())
]
),
// 2a * b = a + b + c - 1
Xnor => Constraint(vec![(FieldT::from(2), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![
(FieldT::one(), i[0].clone()),
(FieldT::one(), i[1].clone()),
(FieldT::one(), o[0].clone()),
(-FieldT::one(), Var::one())
]
),
// a * (1 - b) = c
MaterialNonimplication => Constraint(vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::one(), Var::one()),
(-FieldT::one(), i[1].clone())
],
vec![(FieldT::one(), o[0].clone())]
),
// a * b = a + c - 1
MaterialImplication => Constraint(vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![(FieldT::one(), i[0].clone()),
(FieldT::one(), o[0].clone()),
(-FieldT::one(), Var::one())
]
),
// (1 - a) * (1 - b) = c
Nor => Constraint(vec![(FieldT::one(), Var::one()),
(-FieldT::one(), i[0].clone())
],
vec![(FieldT::one(), Var::one()),
(-FieldT::one(), i[1].clone())
],
vec![(FieldT::one(), o[0].clone())]
),
// a * b = a + b - c
Or => Constraint(vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::one(), i[1].clone())],
vec![(FieldT::one(), i[0].clone()),
(FieldT::one(), i[1].clone()),
(-FieldT::one(), o[0].clone())
]
),
});
vec![o[0]]
@ -263,7 +317,13 @@ impl Bit {
pub fn new(v: &Var) -> Bit {
Is(gadget(&[v], 0, |_| {}, |i, o, cs| {
cs.push(Constraint::Bitness(i[0].index()));
// boolean constraint:
// (1 - a) * a = 0
cs.push(Constraint(vec![(FieldT::one(), Var::one()),
(-FieldT::one(), i[0].clone())],
vec![(FieldT::one(), i[0].clone())],
vec![(FieldT::zero(), Var::one())]
));
vec![i[0]]
}).remove(0))

36
src/variable.rs
View File

@ -1,7 +1,6 @@
use tinysnark::FieldT;
use std::cell::Cell;
use std::rc::Rc;
use std::fmt;
use std::collections::BTreeMap;
pub type WitnessMap = BTreeMap<usize, Vec<(Vec<usize>, Vec<usize>, Rc<Fn(&mut VariableView) + 'static>)>>;
@ -41,33 +40,7 @@ pub fn witness_field_elements(vars: &mut [FieldT], witness_map: &WitnessMap) {
}
#[derive(Clone)]
pub enum Constraint {
Bitness(Rc<Cell<usize>>),
And(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
Nand(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
Xor(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
Xnor(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
MaterialNonimplication(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
MaterialImplication(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
Nor(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>),
Or(Rc<Cell<usize>>, Rc<Cell<usize>>, Rc<Cell<usize>>)
}
impl fmt::Debug for Constraint {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "{}", match *self {
Constraint::Bitness(ref b) => format!("bitness: {}", b.get()),
Constraint::And(ref a, ref b, ref c) => format!("{} = {} AND {}", c.get(), a.get(), b.get()),
Constraint::Nand(ref a, ref b, ref c) => format!("{} = {} NAND {}", c.get(), a.get(), b.get()),
Constraint::Xor(ref a, ref b, ref c) => format!("{} = {} XOR {}", c.get(), a.get(), b.get()),
Constraint::Xnor(ref a, ref b, ref c) => format!("{} = {} XNOR {}", c.get(), a.get(), b.get()),
Constraint::MaterialNonimplication(ref a, ref b, ref c) => format!("{} = {} ↛ {}", c.get(), a.get(), b.get()),
Constraint::MaterialImplication(ref a, ref b, ref c) => format!("{} = {} <-> {}", c.get(), a.get(), b.get()),
Constraint::Nor(ref a, ref b, ref c) => format!("{} = {} NOR {}", c.get(), a.get(), b.get()),
Constraint::Or(ref a, ref b, ref c) => format!("{} = {} OR {}", c.get(), a.get(), b.get())
})
}
}
pub struct Constraint(pub Vec<(FieldT, Var)>, pub Vec<(FieldT, Var)>, pub Vec<(FieldT, Var)>);
struct Gadget {
inputs: Vec<Var>,
@ -122,6 +95,13 @@ impl Var {
}
}
pub fn one() -> Var {
Var {
index: Rc::new(Cell::new(0)),
gadget: None
}
}
// make this not public or unsafe too
pub fn index(&self) -> Rc<Cell<usize>> {
self.index.clone()