parallelize mpt updates (#99)

* parallelize mpt updates

* fix

* remove unnecessary log

* add ci task for testing parallel assignment

* fix all_paddings test failure

* collect runtime statistics

* defer invert to be batched

* fix

* assign_par for key_bit gadget

* assign_par for canonical_repr gadget

* comment

* fix lock file merge errors

---------

Co-authored-by: z2trillion <dawnofthedinosaurs@gmail.com>
Co-authored-by: Mason Liang <mason@scroll.io>

.github/workflows/ci.yml

@@ -34,7 +34,19 @@ jobs:
           toolchain: nightly-2022-12-10
           override: true
       - run: make test
-  bench:
+
+  par-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: nightly-2022-12-10
+          override: true
+      - run: make test_par
+
+   bench:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3

Cargo.toml

@@ -21,6 +21,7 @@ num-bigint = "0.4"
 hex = "0.4"
 thiserror = "1.0"
 log = "0.4"
+env_logger = "0.9.0"
 mpt-zktrie = { git = "https://github.com/scroll-tech/zkevm-circuits.git", rev = "7d9bc181953cfc6e7baf82ff0ce651281fd70a8a" }
 rand_chacha = "0.3.0"
 criterion = { version = "0.4", optional = true}
@@ -33,7 +34,8 @@ ethers-core = { git = "https://github.com/scroll-tech/ethers-rs.git", branch = "
 [features]
 # printout the layout of circuits for demo and some unittests
 print_layout = ["halo2_proofs/dev-graph"]
-bench = [ "dep:criterion" ]
+default = ["halo2_proofs/mock-batch-inv", "halo2_proofs/parallel_syn"]
+bench = ["dep:criterion"]
 
 [dev-dependencies]
 # mpt-zktrie = { path = "../scroll-circuits/zktrie" }
@@ -52,4 +54,4 @@ debug-assertions = true
 [[bench]]
 name = "parallel_assignment"
 harness = false
-required-features = [ "bench" ]
+required-features = ["bench"]

Makefile

@@ -1,6 +1,9 @@
 test:
 	@cargo test
 
+test_par:
+	PARALLEL_SYN=true cargo test -- --nocapture
+
 fmt:
 	@cargo fmt
 

src/constraint_builder/column.rs

@@ -1,4 +1,5 @@
 use super::{BinaryQuery, Query};
+use halo2_proofs::plonk::Assigned;
 use halo2_proofs::{
     arithmetic::FieldExt,
     circuit::{Region, Value},
@@ -101,6 +102,17 @@ impl AdviceColumn {
             )
             .expect("failed assign_advice");
     }
+
+    pub fn assign_rational<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, F>,
+        offset: usize,
+        value: Assigned<F>,
+    ) {
+        region
+            .assign_advice(|| "advice", self.0, offset, || Value::known(value))
+            .expect("failed assign_advice");
+    }
 }
 
 #[derive(Clone, Copy)]

src/gadgets/canonical_representation.rs

@@ -4,6 +4,8 @@ use super::super::constraint_builder::{
 };
 use super::{byte_bit::RangeCheck256Lookup, is_zero::IsZeroGadget, rlc_randomness::RlcRandomness};
 use ethers_core::types::U256;
+use halo2_proofs::circuit::Layouter;
+use halo2_proofs::plonk::Error;
 use halo2_proofs::{
     arithmetic::{Field, FieldExt},
     circuit::{Region, Value},
@@ -212,6 +214,97 @@ impl CanonicalRepresentationConfig {
         }
     }
 
+    pub fn assign_par(
+        &self,
+        layouter: &mut impl Layouter<Fr>,
+        randomness: Value<Fr>,
+        values: &[Fr],
+        n_rows: usize,
+    ) {
+        let modulus = U256::from_str_radix(Fr::MODULUS, 16).unwrap();
+        let mut modulus_bytes = [0u8; 32];
+        modulus.to_big_endian(&mut modulus_bytes);
+
+        let num_threads = std::thread::available_parallelism().unwrap().get();
+        let num_values = n_rows / 32;
+        let zero = Fr::zero();
+        log::debug!("num_real_values: {}", values.len());
+        let values = values
+            .iter()
+            .chain(std::iter::repeat(&zero))
+            .take(num_values)
+            .collect_vec();
+        let chunk_size = (num_values + num_threads - 1) / num_threads;
+        let mut is_first_passes = vec![true; num_threads];
+        let assignments = values
+            .chunks(chunk_size)
+            .zip(is_first_passes.iter_mut())
+            .enumerate()
+            .map(|(i, (values, is_first_pass))| {
+                move |mut region: Region<'_, Fr>| -> Result<(), Error> {
+                    let region = &mut region;
+                    if *is_first_pass {
+                        *is_first_pass = false;
+                        let last_off = if i == 0 {
+                            values.len() * 32
+                        } else {
+                            values.len() * 32 - 1
+                        };
+                        self.value.assign(region, last_off, Fr::zero());
+                        return Ok(());
+                    }
+                    let mut offset = if i == 0 { 1 } else { 0 };
+                    for value in values.iter() {
+                        let mut bytes = value.to_bytes();
+                        bytes.reverse();
+                        let mut differences_are_zero_so_far = true;
+                        let mut rlc = Value::known(Fr::zero());
+                        for (index, (byte, modulus_byte)) in
+                            bytes.iter().zip_eq(&modulus_bytes).enumerate()
+                        {
+                            self.byte.assign(region, offset, u64::from(*byte));
+                            self.modulus_byte
+                                .assign(region, offset, u64::from(*modulus_byte));
+
+                            self.index
+                                .assign(region, offset, u64::try_from(index).unwrap());
+                            if index.is_zero() {
+                                self.index_is_zero.enable(region, offset);
+                            } else if index == 31 {
+                                self.index_is_31.enable(region, offset);
+                            }
+
+                            let difference =
+                                Fr::from(u64::from(*modulus_byte)) - Fr::from(u64::from(*byte));
+                            self.difference.assign(region, offset, difference);
+                            self.difference_is_zero.assign(region, offset, difference);
+
+                            self.differences_are_zero_so_far.assign(
+                                region,
+                                offset,
+                                differences_are_zero_so_far,
+                            );
+                            differences_are_zero_so_far &= difference.is_zero_vartime();
+
+                            self.value.assign(region, offset, **value);
+
+                            rlc = rlc * randomness + Value::known(Fr::from(u64::from(*byte)));
+                            self.rlc.assign(region, offset, rlc);
+
+                            offset += 1
+                        }
+                    }
+
+                    Ok(())
+                }
+            })
+            .collect_vec();
+
+        layouter
+            .assign_regions(|| "canonical_repr", assignments)
+            .unwrap();
+    }
+
     pub fn n_rows_required(values: &[Fr]) -> usize {
         // +1 because assigment starts on offset = 1 instead of offset = 0.
         values.len() * 32 + 1

src/gadgets/is_zero.rs

@@ -1,4 +1,5 @@
 use crate::constraint_builder::{AdviceColumn, BinaryQuery, ConstraintBuilder, Query};
+use halo2_proofs::plonk::Assigned;
 use halo2_proofs::{arithmetic::FieldExt, circuit::Region, plonk::ConstraintSystem};
 use std::fmt::Debug;
 
@@ -25,10 +26,11 @@ impl IsZeroGadget {
     ) where
         <T as TryInto<F>>::Error: Debug,
     {
-        self.inverse_or_zero.assign(
+        self.inverse_or_zero.assign_rational(
             region,
             offset,
-            value.try_into().unwrap().invert().unwrap_or(F::zero()),
+            // invert is deferred and then batched by the real/mock prover
+            Assigned::<F>::from(value.try_into().unwrap()).invert(),
         );
     }
 

src/gadgets/key_bit.rs

@@ -3,9 +3,11 @@ use super::{
     canonical_representation::CanonicalRepresentationLookup,
 };
 use crate::constraint_builder::{AdviceColumn, ConstraintBuilder, Query};
+use halo2_proofs::circuit::Layouter;
 use halo2_proofs::{
     arithmetic::FieldExt, circuit::Region, halo2curves::bn256::Fr, plonk::ConstraintSystem,
 };
+use itertools::Itertools;
 
 pub trait KeyBitLookup {
     fn lookup<F: FieldExt>(&self) -> [Query<F>; 3];
@@ -83,10 +85,22 @@ impl KeyBitConfig {
     }
 
     pub fn assign(&self, region: &mut Region<'_, Fr>, lookups: &[(Fr, usize, bool)]) {
+        self.assign_internal(region, lookups, false)
+    }
+    pub fn assign_internal(
+        &self,
+        region: &mut Region<'_, Fr>,
+        lookups: &[(Fr, usize, bool)],
+        use_par: bool,
+    ) {
         // TODO; dedup lookups
         for (offset, (value, index, bit)) in lookups.iter().enumerate() {
             // TODO: either move the disabled row to the end of the assigment or get rid of it entirely.
-            let offset = offset + 1; // Start assigning at offet = 1 because the first row is disabled.
+            let offset = if !use_par {
+                offset + 1 // Start assigning at offet = 1 because the first row is disabled.
+            } else {
+                offset
+            };
             let bytes = value.to_bytes();
 
             let index_div_8 = index / 8; // index = (31 - index/8) * 8
@@ -107,6 +121,43 @@ impl KeyBitConfig {
         }
     }
 
+    pub fn assign_par(&self, layouter: &mut impl Layouter<Fr>, lookups: &[(Fr, usize, bool)]) {
+        let num_threads = std::thread::available_parallelism()
+            .expect("get num threads")
+            .get();
+        let chunk_size = (lookups.len() + num_threads - 1) / num_threads;
+        let mut is_first_pass = vec![true; num_threads];
+        let assignments = lookups
+            .chunks(chunk_size)
+            .zip(is_first_pass.iter_mut())
+            .enumerate()
+            .map(|(i, (lookups, is_first_pass))| {
+                move |mut region: Region<'_, Fr>| {
+                    if *is_first_pass {
+                        *is_first_pass = false;
+
+                        if !lookups.is_empty() {
+                            // only meant to get region's shape.
+                            let last_off = if i == 0 {
+                                // 1st row is disabled.
+                                lookups.len()
+                            } else {
+                                lookups.len() - 1
+                            };
+                            self.byte.assign(&mut region, last_off, 0_u64);
+                        }
+                        return Ok(());
+                    }
+                    self.assign_internal(&mut region, lookups, true);
+
+                    Ok(())
+                }
+            })
+            .collect_vec();
+
+        layouter.assign_regions(|| "key_bit", assignments).unwrap();
+    }
+
     pub fn n_rows_required(lookups: &[(Fr, usize, bool)]) -> usize {
         // +1 because assigment starts on offset = 1 instead of offset = 0.
         1 + lookups.len()