feat: send sync region

halo2_proofs/Cargo.toml

@@ -77,6 +77,7 @@ getrandom = { version = "0.2", features = ["js"] }
 default = ["batch"]
 dev-graph = ["plotters", "tabbycat"]
 gadget-traces = ["backtrace"]
+thread-safe-region = []
 sanity-checks = []
 batch = ["rand_core/getrandom"]
 circuit-params = []
@@ -87,3 +88,5 @@ bench = false
 [[example]]
 name = "circuit-layout"
 required-features = ["dev-graph"]
+
+

halo2_proofs/examples/vector-mul.rs

@@ -0,0 +1,350 @@
+use std::marker::PhantomData;
+
+use halo2_proofs::{
+    arithmetic::Field,
+    circuit::{AssignedCell, Chip, Layouter, Region, SimpleFloorPlanner, Value},
+    plonk::{Advice, Circuit, Column, ConstraintSystem, Error, Instance, Selector},
+    poly::Rotation,
+};
+
+// ANCHOR: instructions
+trait NumericInstructions<F: Field>: Chip<F> {
+    /// Variable representing a number.
+    type Num;
+
+    /// Loads a number into the circuit as a private input.
+    fn load_private(
+        &self,
+        layouter: impl Layouter<F>,
+        a: &[Value<F>],
+    ) -> Result<Vec<Self::Num>, Error>;
+
+    /// Returns `c = a * b`. The caller is responsible for ensuring that `a.len() == b.len()`.
+    fn mul(
+        &self,
+        layouter: impl Layouter<F>,
+        a: &[Self::Num],
+        b: &[Self::Num],
+    ) -> Result<Vec<Self::Num>, Error>;
+
+    /// Exposes a number as a public input to the circuit.
+    fn expose_public(
+        &self,
+        layouter: impl Layouter<F>,
+        num: &Self::Num,
+        row: usize,
+    ) -> Result<(), Error>;
+}
+// ANCHOR_END: instructions
+
+// ANCHOR: chip
+/// The chip that will implement our instructions! Chips store their own
+/// config, as well as type markers if necessary.
+struct FieldChip<F: Field> {
+    config: FieldConfig,
+    _marker: PhantomData<F>,
+}
+// ANCHOR_END: chip
+
+// ANCHOR: chip-config
+/// Chip state is stored in a config struct. This is generated by the chip
+/// during configuration, and then stored inside the chip.
+#[derive(Clone, Debug)]
+struct FieldConfig {
+    /// For this chip, we will use two advice columns to implement our instructions.
+    /// These are also the columns through which we communicate with other parts of
+    /// the circuit.
+    advice: [Column<Advice>; 3],
+
+    /// This is the public input (instance) column.
+    instance: Column<Instance>,
+
+    // We need a selector to enable the multiplication gate, so that we aren't placing
+    // any constraints on cells where `NumericInstructions::mul` is not being used.
+    // This is important when building larger circuits, where columns are used by
+    // multiple sets of instructions.
+    s_mul: Selector,
+}
+
+impl<F: Field> FieldChip<F> {
+    fn construct(config: <Self as Chip<F>>::Config) -> Self {
+        Self {
+            config,
+            _marker: PhantomData,
+        }
+    }
+
+    fn configure(
+        meta: &mut ConstraintSystem<F>,
+        advice: [Column<Advice>; 3],
+        instance: Column<Instance>,
+    ) -> <Self as Chip<F>>::Config {
+        meta.enable_equality(instance);
+        for column in &advice {
+            meta.enable_equality(*column);
+        }
+        let s_mul = meta.selector();
+
+        // Define our multiplication gate!
+        meta.create_gate("mul", |meta| {
+            // To implement multiplication, we need three advice cells and a selector
+            // cell. We arrange them like so:
+            //
+            // | a0  | a1  | a2  | s_mul |
+            // |-----|-----|-----|-------|
+            // | lhs | rhs | out | s_mul |
+            //
+            // Gates may refer to any relative offsets we want, but each distinct
+            // offset adds a cost to the proof. The most common offsets are 0 (the
+            // current row), 1 (the next row), and -1 (the previous row), for which
+            // `Rotation` has specific constructors.
+            let lhs = meta.query_advice(advice[0], Rotation::cur());
+            let rhs = meta.query_advice(advice[1], Rotation::cur());
+            let out = meta.query_advice(advice[2], Rotation::cur());
+            let s_mul = meta.query_selector(s_mul);
+
+            // Finally, we return the polynomial expressions that constrain this gate.
+            // For our multiplication gate, we only need a single polynomial constraint.
+            //
+            // The polynomial expressions returned from `create_gate` will be
+            // constrained by the proving system to equal zero. Our expression
+            // has the following properties:
+            // - When s_mul = 0, any value is allowed in lhs, rhs, and out.
+            // - When s_mul != 0, this constrains lhs * rhs = out.
+            vec![s_mul * (lhs * rhs - out)]
+        });
+
+        FieldConfig {
+            advice,
+            instance,
+            s_mul,
+        }
+    }
+}
+// ANCHOR_END: chip-config
+
+// ANCHOR: chip-impl
+impl<F: Field> Chip<F> for FieldChip<F> {
+    type Config = FieldConfig;
+    type Loaded = ();
+
+    fn config(&self) -> &Self::Config {
+        &self.config
+    }
+
+    fn loaded(&self) -> &Self::Loaded {
+        &()
+    }
+}
+// ANCHOR_END: chip-impl
+
+// ANCHOR: instructions-impl
+/// A variable representing a number.
+#[derive(Clone, Debug)]
+struct Number<F: Field>(AssignedCell<F, F>);
+
+impl<F: Field> NumericInstructions<F> for FieldChip<F> {
+    type Num = Number<F>;
+
+    fn load_private(
+        &self,
+        mut layouter: impl Layouter<F>,
+        values: &[Value<F>],
+    ) -> Result<Vec<Self::Num>, Error> {
+        let config = self.config();
+
+        layouter.assign_region(
+            || "load private",
+            |mut region| {
+                values
+                    .iter()
+                    .enumerate()
+                    .map(|(i, value)| {
+                        region
+                            .assign_advice(|| "private input", config.advice[0], i, || *value)
+                            .map(Number)
+                    })
+                    .collect()
+            },
+        )
+    }
+
+    fn mul(
+        &self,
+        mut layouter: impl Layouter<F>,
+        a: &[Self::Num],
+        b: &[Self::Num],
+    ) -> Result<Vec<Self::Num>, Error> {
+        let config = self.config();
+        assert_eq!(a.len(), b.len());
+
+        #[cfg(feature = "thread-safe-region")]
+        {
+            use rayon::prelude::{
+                IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator,
+            };
+            layouter.assign_region(
+                || "mul",
+                |region: Region<'_, F>| {
+                    let thread_safe_region = std::sync::Mutex::new(region);
+                    a.par_iter()
+                        .zip(b.par_iter())
+                        .enumerate()
+                        .map(|(i, (a, b))| {
+                            let mut region = thread_safe_region.lock().unwrap();
+
+                            config.s_mul.enable(&mut region, i)?;
+
+                            a.0.copy_advice(|| "lhs", &mut region, config.advice[0], i)?;
+                            b.0.copy_advice(|| "rhs", &mut region, config.advice[1], i)?;
+
+                            let value = a.0.value().copied() * b.0.value();
+
+                            // Finally, we do the assignment to the output, returning a
+                            // variable to be used in another part of the circuit.
+                            region
+                                .assign_advice(|| "lhs * rhs", config.advice[2], i, || value)
+                                .map(Number)
+                        })
+                        .collect()
+                },
+            )
+        }
+
+        #[cfg(not(feature = "thread-safe-region"))]
+        layouter.assign_region(
+            || "mul",
+            |mut region: Region<'_, F>| {
+                a.iter()
+                    .zip(b.iter())
+                    .enumerate()
+                    .map(|(i, (a, b))| {
+                        config.s_mul.enable(&mut region, i)?;
+
+                        a.0.copy_advice(|| "lhs", &mut region, config.advice[0], i)?;
+                        b.0.copy_advice(|| "rhs", &mut region, config.advice[1], i)?;
+
+                        let value = a.0.value().copied() * b.0.value();
+
+                        // Finally, we do the assignment to the output, returning a
+                        // variable to be used in another part of the circuit.
+                        region
+                            .assign_advice(|| "lhs * rhs", config.advice[2], i, || value)
+                            .map(Number)
+                    })
+                    .collect()
+            },
+        )
+    }
+
+    fn expose_public(
+        &self,
+        mut layouter: impl Layouter<F>,
+        num: &Self::Num,
+        row: usize,
+    ) -> Result<(), Error> {
+        let config = self.config();
+
+        layouter.constrain_instance(num.0.cell(), config.instance, row)
+    }
+}
+// ANCHOR_END: instructions-impl
+
+// ANCHOR: circuit
+/// The full circuit implementation.
+///
+/// In this struct we store the private input variables. We use `Option<F>` because
+/// they won't have any value during key generation. During proving, if any of these
+/// were `None` we would get an error.
+#[derive(Default)]
+struct MyCircuit<F: Field> {
+    a: Vec<Value<F>>,
+    b: Vec<Value<F>>,
+}
+
+impl<F: Field> Circuit<F> for MyCircuit<F> {
+    // Since we are using a single chip for everything, we can just reuse its config.
+    type Config = FieldConfig;
+    type FloorPlanner = SimpleFloorPlanner;
+    #[cfg(feature = "circuit-params")]
+    type Params = ();
+
+    fn without_witnesses(&self) -> Self {
+        Self::default()
+    }
+
+    fn configure(meta: &mut ConstraintSystem<F>) -> Self::Config {
+        // We create the three advice columns that FieldChip uses for I/O.
+        let advice = [
+            meta.advice_column(),
+            meta.advice_column(),
+            meta.advice_column(),
+        ];
+
+        // We also need an instance column to store public inputs.
+        let instance = meta.instance_column();
+
+        FieldChip::configure(meta, advice, instance)
+    }
+
+    fn synthesize(
+        &self,
+        config: Self::Config,
+        mut layouter: impl Layouter<F>,
+    ) -> Result<(), Error> {
+        let field_chip = FieldChip::<F>::construct(config);
+
+        // Load our private values into the circuit.
+        let a = field_chip.load_private(layouter.namespace(|| "load a"), &self.a)?;
+        let b = field_chip.load_private(layouter.namespace(|| "load b"), &self.b)?;
+
+        let ab = field_chip.mul(layouter.namespace(|| "a * b"), &a, &b)?;
+
+        for (i, c) in ab.iter().enumerate() {
+            // Expose the result as a public input to the circuit.
+            field_chip.expose_public(layouter.namespace(|| "expose c"), c, i)?;
+        }
+        Ok(())
+    }
+}
+// ANCHOR_END: circuit
+
+fn main() {
+    use halo2_proofs::dev::MockProver;
+    use halo2curves::pasta::Fp;
+
+    const N: usize = 20000;
+    // ANCHOR: test-circuit
+    // The number of rows in our circuit cannot exceed 2^k. Since our example
+    // circuit is very small, we can pick a very small value here.
+    let k = 16;
+
+    // Prepare the private and public inputs to the circuit!
+    let a = [Fp::from(2); N];
+    let b = [Fp::from(3); N];
+    let c: Vec<Fp> = a.iter().zip(b).map(|(&a, b)| a * b).collect();
+
+    // Instantiate the circuit with the private inputs.
+    let circuit = MyCircuit {
+        a: a.iter().map(|&x| Value::known(x)).collect(),
+        b: b.iter().map(|&x| Value::known(x)).collect(),
+    };
+
+    // Arrange the public input. We expose the multiplication result in row 0
+    // of the instance column, so we position it there in our public inputs.
+    let mut public_inputs = c;
+
+    let start = std::time::Instant::now();
+    // Given the correct public input, our circuit will verify.
+    let prover = MockProver::run(k, &circuit, vec![public_inputs.clone()]).unwrap();
+    assert_eq!(prover.verify(), Ok(()));
+    println!("positive test took {:?}", start.elapsed());
+
+    // If we try some other public input, the proof will fail!
+    let start = std::time::Instant::now();
+    public_inputs[0] += Fp::one();
+    let prover = MockProver::run(k, &circuit, vec![public_inputs]).unwrap();
+    assert!(prover.verify().is_err());
+    println!("negative test took {:?}", start.elapsed());
+    // ANCHOR_END: test-circuit
+}