ysbell/gadgets/
multieq.rs

1use ff::{Field, PrimeField, ScalarEngine};
2
3use crate::{ConstraintSystem, LinearCombination, SynthesisError, Variable};
4
5pub struct MultiEq<E: ScalarEngine, CS: ConstraintSystem<E>> {
6    cs: CS,
7    ops: usize,
8    bits_used: usize,
9    lhs: LinearCombination<E>,
10    rhs: LinearCombination<E>,
11}
12
13impl<E: ScalarEngine, CS: ConstraintSystem<E>> MultiEq<E, CS> {
14    pub fn new(cs: CS) -> Self {
15        MultiEq {
16            cs,
17            ops: 0,
18            bits_used: 0,
19            lhs: LinearCombination::zero(),
20            rhs: LinearCombination::zero(),
21        }
22    }
23
24    fn accumulate(&mut self) {
25        let ops = self.ops;
26        let lhs = self.lhs.clone();
27        let rhs = self.rhs.clone();
28        self.cs.enforce(
29            || format!("multieq {}", ops),
30            |_| lhs,
31            |lc| lc + CS::one(),
32            |_| rhs,
33        );
34        self.lhs = LinearCombination::zero();
35        self.rhs = LinearCombination::zero();
36        self.bits_used = 0;
37        self.ops += 1;
38    }
39
40    pub fn enforce_equal(
41        &mut self,
42        num_bits: usize,
43        lhs: &LinearCombination<E>,
44        rhs: &LinearCombination<E>,
45    ) {
46        // Check if we will exceed the capacity
47        if (E::Fr::CAPACITY as usize) <= (self.bits_used + num_bits) {
48            self.accumulate();
49        }
50
51        assert!((E::Fr::CAPACITY as usize) > (self.bits_used + num_bits));
52
53        let coeff = E::Fr::from_str("2").unwrap().pow(&[self.bits_used as u64]);
54        self.lhs = self.lhs.clone() + (coeff, lhs);
55        self.rhs = self.rhs.clone() + (coeff, rhs);
56        self.bits_used += num_bits;
57    }
58}
59
60impl<E: ScalarEngine, CS: ConstraintSystem<E>> Drop for MultiEq<E, CS> {
61    fn drop(&mut self) {
62        if self.bits_used > 0 {
63            self.accumulate();
64        }
65    }
66}
67
68impl<E: ScalarEngine, CS: ConstraintSystem<E>> ConstraintSystem<E> for MultiEq<E, CS> {
69    type Root = Self;
70
71    fn one() -> Variable {
72        CS::one()
73    }
74
75    fn alloc<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
76    where
77        F: FnOnce() -> Result<E::Fr, SynthesisError>,
78        A: FnOnce() -> AR,
79        AR: Into<String>,
80    {
81        self.cs.alloc(annotation, f)
82    }
83
84    fn alloc_input<F, A, AR>(&mut self, annotation: A, f: F) -> Result<Variable, SynthesisError>
85    where
86        F: FnOnce() -> Result<E::Fr, SynthesisError>,
87        A: FnOnce() -> AR,
88        AR: Into<String>,
89    {
90        self.cs.alloc_input(annotation, f)
91    }
92
93    fn enforce<A, AR, LA, LB, LC>(&mut self, annotation: A, a: LA, b: LB, c: LC)
94    where
95        A: FnOnce() -> AR,
96        AR: Into<String>,
97        LA: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
98        LB: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
99        LC: FnOnce(LinearCombination<E>) -> LinearCombination<E>,
100    {
101        self.cs.enforce(annotation, a, b, c)
102    }
103
104    fn push_namespace<NR, N>(&mut self, name_fn: N)
105    where
106        NR: Into<String>,
107        N: FnOnce() -> NR,
108    {
109        self.cs.get_root().push_namespace(name_fn)
110    }
111
112    fn pop_namespace(&mut self) {
113        self.cs.get_root().pop_namespace()
114    }
115
116    fn get_root(&mut self) -> &mut Self::Root {
117        self
118    }
119}
ysbell/gadgets/multieq.rs

ysbell/gadgets/
multieq.rs
