change: Move from maybe_rayon to rayon-1.8

.github/workflows/ci.yml

@@ -32,7 +32,6 @@ env:
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
   cancel-in-progress: true
-
 
 jobs:
   test:
@@ -42,8 +41,10 @@ jobs:
     strategy:
       matrix:
         include:
-          - feature: 
           - feature: default
+        target:
+          - wasm32-unknown-unknown
+          - wasm32-wasi
     steps:
       - uses: actions/checkout@v2
       - uses: actions-rs/toolchain@v1
@@ -54,6 +55,10 @@ jobs:
         # This build will be reused by nextest,
         # and also checks (--all-targets) that benches don't bit-rot
         run: cargo build --release --all-targets --no-default-features --features "${{ matrix.feature }}"
+        # We run WASM build (for tests) which compiles the lib allowig us to have
+        # `getrandom` as a dev-dependency.
+      - name: Build (WASM compat)
+        run: cargo build --tests --release --no-default-features --features "${{ matrix.feature }}"
       - name: Test
         run: |
           cargo nextest run --profile ci --release --workspace --no-default-features --features "${{ matrix.feature }}"

Cargo.toml

@@ -18,6 +18,11 @@ serde_json = "1.0.105"
 hex = "0.4"
 rand_chacha = "0.3.1"
 
+# Added to make sure we are able to build the lib in the CI.
+# Notice this will never be loaded for someone using this lib as dep.
+[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dev-dependencies]
+getrandom = { version = "0.2", features = ["js"] }
+
 [dependencies]
 subtle = "2.4"
 ff = { version = "0.13.0", default-features = false, features = ["std"] }
@@ -35,11 +40,10 @@ serde = { version = "1.0", default-features = false, optional = true }
 serde_arrays = { version = "0.1.0", optional = true }
 hex = { version = "0.4", optional = true, default-features = false, features = ["alloc", "serde"] }
 blake2b_simd = "1"
-maybe-rayon = { version = "0.1.0", default-features = false }
+rayon = "1.8"
 
 [features]
-default = ["bits", "multicore"]
-multicore = ["maybe-rayon/threads"]
+default = ["bits"]
 asm = []
 bits = ["ff/bits"]
 bn256-table = []

README.md

@@ -17,6 +17,19 @@ The implementations were originally ported from [matterlabs/pairing](https://git
 * Various features related to serialization and deserialization of curve points and field elements.
 * Curve-specific optimizations and benchmarking capabilities.
 
+## Controlling parallelism
+
+`halo2curves` currently uses [rayon](https://github.com/rayon-rs/rayon) for parallel
+computation. 
+
+The `RAYON_NUM_THREADS` environment variable can be used to set the number of
+threads.
+
+When compiling to WASM-targets, notice that since version `1.7`, `rayon` will fallback automatically (with no need to handle features) to require `getrandom` in order to be able to work.
+For more info related to WASM-compilation.
+
+See: [Rayon: Usage with WebAssembly](https://github.com/rayon-rs/rayon#usage-with-webassembly) for more info.  
+
 ## Benchmarks
 
 Benchmarking is supported through the use of Rust's built-in test framework. Benchmarks can be run without assembly optimizations:

src/fft.rs

@@ -1,4 +1,3 @@
-use crate::multicore;
 pub use crate::{CurveAffine, CurveExt};
 use ff::Field;
 use group::{GroupOpsOwned, ScalarMulOwned};
@@ -38,7 +37,7 @@ pub fn best_fft<Scalar: Field, G: FftGroup<Scalar>>(a: &mut [G], omega: Scalar,
         r
     }
 
-    let threads = multicore::current_num_threads();
+    let threads = rayon::current_num_threads();
     let log_threads = threads.ilog2();
     let n = a.len();
     assert_eq!(n, 1 << log_n);
@@ -107,7 +106,7 @@ pub fn recursive_butterfly_arithmetic<Scalar: Field, G: FftGroup<Scalar>>(
         a[1] -= &t;
     } else {
         let (left, right) = a.split_at_mut(n / 2);
-        multicore::join(
+        rayon::join(
             || recursive_butterfly_arithmetic(left, n / 2, twiddle_chunk * 2, twiddles),
             || recursive_butterfly_arithmetic(right, n / 2, twiddle_chunk * 2, twiddles),
         );

src/lib.rs

@@ -3,7 +3,6 @@ pub mod ff_ext;
 pub mod fft;
 pub mod hash_to_curve;
 pub mod msm;
-pub mod multicore;
 pub mod serde;
 
 pub mod bn256;

src/msm.rs

@@ -4,8 +4,6 @@ use ff::PrimeField;
 use group::Group;
 use pasta_curves::arithmetic::CurveAffine;
 
-use crate::multicore;
-
 fn get_booth_index(window_index: usize, window_size: usize, el: &[u8]) -> i32 {
     // Booth encoding:
     // * step by `window` size
@@ -155,12 +153,12 @@ pub fn small_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::C
 pub fn best_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::Curve {
     assert_eq!(coeffs.len(), bases.len());
 
-    let num_threads = multicore::current_num_threads();
+    let num_threads = rayon::current_num_threads();
     if coeffs.len() > num_threads {
         let chunk = coeffs.len() / num_threads;
         let num_chunks = coeffs.chunks(chunk).len();
         let mut results = vec![C::Curve::identity(); num_chunks];
-        multicore::scope(|scope| {
+        rayon::scope(|scope| {
             let chunk = coeffs.len() / num_threads;
 
             for ((coeffs, bases), acc) in coeffs
@@ -186,10 +184,7 @@ mod test {
 
     use std::ops::Neg;
 
-    use crate::{
-        bn256::{Fr, G1Affine, G1},
-        multicore,
-    };
+    use crate::bn256::{Fr, G1Affine, G1};
     use ark_std::{end_timer, start_timer};
     use ff::{Field, PrimeField};
     use group::{Curve, Group};
@@ -200,12 +195,12 @@ mod test {
     fn best_multiexp<C: CurveAffine>(coeffs: &[C::Scalar], bases: &[C]) -> C::Curve {
         assert_eq!(coeffs.len(), bases.len());
 
-        let num_threads = multicore::current_num_threads();
+        let num_threads = rayon::current_num_threads();
         if coeffs.len() > num_threads {
             let chunk = coeffs.len() / num_threads;
             let num_chunks = coeffs.chunks(chunk).len();
             let mut results = vec![C::Curve::identity(); num_chunks];
-            multicore::scope(|scope| {
+            rayon::scope(|scope| {
                 let chunk = coeffs.len() / num_threads;
 
                 for ((coeffs, bases), acc) in coeffs