halo2/examples/circuit-layout.rs

use halo2::{
    arithmetic::FieldExt,
    circuit::{Cell, Layouter, Region, SimpleFloorPlanner},
    dev::CircuitLayout,
    pasta::Fp,
    plonk::{Advice, Circuit, Column, ConstraintSystem, Error, Fixed, TableColumn},
    poly::Rotation,
};
use plotters::prelude::*;
use std::marker::PhantomData;

#[allow(clippy::many_single_char_names)]
fn main() {
    /// This represents an advice column at a certain row in the ConstraintSystem
    #[derive(Copy, Clone, Debug)]
    pub struct Variable(Column<Advice>, usize);

    #[derive(Clone)]
    struct PlonkConfig {
        a: Column<Advice>,
        b: Column<Advice>,
        c: Column<Advice>,
        d: Column<Advice>,
        e: Column<Advice>,

        sa: Column<Fixed>,
        sb: Column<Fixed>,
        sc: Column<Fixed>,
        sm: Column<Fixed>,
        sl: TableColumn,
    }

    trait StandardCs<FF: FieldExt> {
        fn raw_multiply<F>(
            &self,
            region: &mut Region<FF>,
            f: F,
        ) -> Result<(Cell, Cell, Cell), Error>
        where
            F: FnMut() -> Result<(FF, FF, FF), Error>;
        fn raw_add<F>(&self, region: &mut Region<FF>, f: F) -> Result<(Cell, Cell, Cell), Error>
        where
            F: FnMut() -> Result<(FF, FF, FF), Error>;
        fn copy(&self, region: &mut Region<FF>, a: Cell, b: Cell) -> Result<(), Error>;
        fn lookup_table(
            &self,
            layouter: &mut impl Layouter<FF>,
            values: &[FF],
        ) -> Result<(), Error>;
    }

    struct MyCircuit<F: FieldExt> {
        a: Option<F>,
        lookup_table: Vec<F>,
    }

    struct StandardPlonk<F: FieldExt> {
        config: PlonkConfig,
        _marker: PhantomData<F>,
    }

    impl<FF: FieldExt> StandardPlonk<FF> {
        fn new(config: PlonkConfig) -> Self {
            StandardPlonk {
                config,
                _marker: PhantomData,
            }
        }
    }

    impl<FF: FieldExt> StandardCs<FF> for StandardPlonk<FF> {
        fn raw_multiply<F>(
            &self,
            region: &mut Region<FF>,
            mut f: F,
        ) -> Result<(Cell, Cell, Cell), Error>
        where
            F: FnMut() -> Result<(FF, FF, FF), Error>,
        {
            let mut value = None;
            let lhs = region.assign_advice(
                || "lhs",
                self.config.a,
                0,
                || {
                    value = Some(f()?);
                    Ok(value.ok_or(Error::SynthesisError)?.0)
                },
            )?;
            region.assign_advice(
                || "lhs^4",
                self.config.d,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.0.square().square()),
            )?;
            let rhs = region.assign_advice(
                || "rhs",
                self.config.b,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.1),
            )?;
            region.assign_advice(
                || "rhs^4",
                self.config.e,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.1.square().square()),
            )?;
            let out = region.assign_advice(
                || "out",
                self.config.c,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.2),
            )?;

            region.assign_fixed(|| "a", self.config.sa, 0, || Ok(FF::zero()))?;
            region.assign_fixed(|| "b", self.config.sb, 0, || Ok(FF::zero()))?;
            region.assign_fixed(|| "c", self.config.sc, 0, || Ok(FF::one()))?;
            region.assign_fixed(|| "a * b", self.config.sm, 0, || Ok(FF::one()))?;
            Ok((lhs, rhs, out))
        }
        fn raw_add<F>(&self, region: &mut Region<FF>, mut f: F) -> Result<(Cell, Cell, Cell), Error>
        where
            F: FnMut() -> Result<(FF, FF, FF), Error>,
        {
            let mut value = None;
            let lhs = region.assign_advice(
                || "lhs",
                self.config.a,
                0,
                || {
                    value = Some(f()?);
                    Ok(value.ok_or(Error::SynthesisError)?.0)
                },
            )?;
            region.assign_advice(
                || "lhs^4",
                self.config.d,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.0.square().square()),
            )?;
            let rhs = region.assign_advice(
                || "rhs",
                self.config.b,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.1),
            )?;
            region.assign_advice(
                || "rhs^4",
                self.config.e,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.1.square().square()),
            )?;
            let out = region.assign_advice(
                || "out",
                self.config.c,
                0,
                || Ok(value.ok_or(Error::SynthesisError)?.2),
            )?;

            region.assign_fixed(|| "a", self.config.sa, 0, || Ok(FF::one()))?;
            region.assign_fixed(|| "b", self.config.sb, 0, || Ok(FF::one()))?;
            region.assign_fixed(|| "c", self.config.sc, 0, || Ok(FF::one()))?;
            region.assign_fixed(|| "a * b", self.config.sm, 0, || Ok(FF::zero()))?;
            Ok((lhs, rhs, out))
        }
        fn copy(&self, region: &mut Region<FF>, left: Cell, right: Cell) -> Result<(), Error> {
            region.constrain_equal(left, right)
        }
        fn lookup_table(
            &self,
            layouter: &mut impl Layouter<FF>,
            values: &[FF],
        ) -> Result<(), Error> {
            layouter.assign_table(
                || "",
                |mut table| {
                    for (index, &value) in values.iter().enumerate() {
                        table.assign_cell(|| "table col", self.config.sl, index, || Ok(value))?;
                    }
                    Ok(())
                },
            )?;
            Ok(())
        }
    }

    impl<F: FieldExt> Circuit<F> for MyCircuit<F> {
        type Config = PlonkConfig;
        type FloorPlanner = SimpleFloorPlanner;

        fn without_witnesses(&self) -> Self {
            Self {
                a: None,
                lookup_table: self.lookup_table.clone(),
            }
        }

        fn configure(meta: &mut ConstraintSystem<F>) -> PlonkConfig {
            let e = meta.advice_column();
            let a = meta.advice_column();
            let b = meta.advice_column();
            let sf = meta.fixed_column();
            let c = meta.advice_column();
            let d = meta.advice_column();

            meta.enable_equality(a.into());
            meta.enable_equality(b.into());
            meta.enable_equality(c.into());

            let sm = meta.fixed_column();
            let sa = meta.fixed_column();
            let sb = meta.fixed_column();
            let sc = meta.fixed_column();
            let sl = meta.lookup_table_column();

            /*
             *   A         B      ...  sl
             * [
             *   instance  0      ...  0
             *   a         a      ...  0
             *   a         a^2    ...  0
             *   a         a      ...  0
             *   a         a^2    ...  0
             *   ...       ...    ...  ...
             *   ...       ...    ...  instance
             *   ...       ...    ...  a
             *   ...       ...    ...  a
             *   ...       ...    ...  0
             * ]
             */
            meta.lookup(|meta| {
                let a_ = meta.query_any(a.into(), Rotation::cur());
                vec![(a_, sl)]
            });

            meta.create_gate("Combined add-mult", |meta| {
                let d = meta.query_advice(d, Rotation::next());
                let a = meta.query_advice(a, Rotation::cur());
                let sf = meta.query_fixed(sf, Rotation::cur());
                let e = meta.query_advice(e, Rotation::prev());
                let b = meta.query_advice(b, Rotation::cur());
                let c = meta.query_advice(c, Rotation::cur());

                let sa = meta.query_fixed(sa, Rotation::cur());
                let sb = meta.query_fixed(sb, Rotation::cur());
                let sc = meta.query_fixed(sc, Rotation::cur());
                let sm = meta.query_fixed(sm, Rotation::cur());

                vec![a.clone() * sa + b.clone() * sb + a * b * sm - (c * sc) + sf * (d * e)]
            });

            PlonkConfig {
                a,
                b,
                c,
                d,
                e,
                sa,
                sb,
                sc,
                sm,
                sl,
            }
        }

        fn synthesize(
            &self,
            config: PlonkConfig,
            mut layouter: impl Layouter<F>,
        ) -> Result<(), Error> {
            let cs = StandardPlonk::new(config);

            for i in 0..10 {
                layouter.assign_region(
                    || format!("region_{}", i),
                    |mut region| {
                        let mut a_squared = None;
                        let (a0, _, c0) = cs.raw_multiply(&mut region, || {
                            a_squared = self.a.map(|a| a.square());
                            Ok((
                                self.a.ok_or(Error::SynthesisError)?,
                                self.a.ok_or(Error::SynthesisError)?,
                                a_squared.ok_or(Error::SynthesisError)?,
                            ))
                        })?;
                        let (a1, b1, _) = cs.raw_add(&mut region, || {
                            let fin = a_squared.and_then(|a2| self.a.map(|a| a + a2));
                            Ok((
                                self.a.ok_or(Error::SynthesisError)?,
                                a_squared.ok_or(Error::SynthesisError)?,
                                fin.ok_or(Error::SynthesisError)?,
                            ))
                        })?;
                        cs.copy(&mut region, a0, a1)?;
                        cs.copy(&mut region, b1, c0)
                    },
                )?;
            }

            cs.lookup_table(&mut layouter, &self.lookup_table)?;

            Ok(())
        }
    }

    let a = Fp::rand();
    let instance = Fp::one() + Fp::one();
    let lookup_table = vec![instance, a, a, Fp::zero()];

    let circuit: MyCircuit<Fp> = MyCircuit {
        a: None,
        lookup_table,
    };

    let root = BitMapBackend::new("example-circuit-layout.png", (1024, 768)).into_drawing_area();
    root.fill(&WHITE).unwrap();
    let root = root
        .titled("Example Circuit Layout", ("sans-serif", 60))
        .unwrap();

    CircuitLayout::default().render(5, &circuit, &root).unwrap();
}