parallelize with rayon

test/check-toolchains/Cargo.lock

@@ -57,6 +57,12 @@ version = "1.0.71"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c7d0618f0e0b7e8ff11427422b64564d5fb0be1940354bfe2e0529b18a9d9b8"
 
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -69,12 +75,19 @@ version = "1.0.79"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "50d30906286121d95be3d479533b458f87493b30a4b5f79a607db8f5d11aa91f"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "check-toolchains"
 version = "0.1.0"
 dependencies = [
  "anyhow",
  "clap",
+ "rayon",
 ]
 
 [[package]]
@@ -125,6 +138,55 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "acbf1af155f9b9ef647e42cdc158db4b64a1b61f743629225fde6f3e0be2a7c7"
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a33c2bf77f2df06183c3aa30d1e96c0695a313d4f9c453cc3762a6db39f99200"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce6fd6f855243022dcecf8702fef0c297d4338e226845fe067f6341ad9fa0cef"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "46bd5f3f85273295a9d14aedfb86f6aadbff6d8f5295c4a9edb08e819dcf5695"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+ "crossbeam-utils",
+ "memoffset",
+ "scopeguard",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c063cd8cc95f5c377ed0d4b49a4b21f632396ff690e8470c29b3359b346984b"
+dependencies = [
+ "cfg-if",
+]
+
+[[package]]
+name = "either"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcaabb2fef8c910e7f4c7ce9f67a1283a1715879a7c230ca9d6d1ae31f16d91"
+
 [[package]]
 name = "errno"
 version = "0.3.1"
@@ -152,6 +214,15 @@ version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
 
+[[package]]
+name = "hermit-abi"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee512640fe35acbfb4bb779db6f0d80704c2cacfa2e39b601ef3e3f47d1ae4c7"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "hermit-abi"
 version = "0.3.1"
@@ -164,7 +235,7 @@ version = "1.0.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c66c74d2ae7e79a5a8f7ac924adbe38ee42a859c6539ad869eb51f0b52dc220"
 dependencies = [
- "hermit-abi",
+ "hermit-abi 0.3.1",
  "libc",
  "windows-sys",
 ]
@@ -175,7 +246,7 @@ version = "0.4.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "adcf93614601c8129ddf72e2d5633df827ba6551541c6d8c59520a371475be1f"
 dependencies = [
- "hermit-abi",
+ "hermit-abi 0.3.1",
  "io-lifetimes",
  "rustix",
  "windows-sys",
@@ -193,6 +264,25 @@ version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ece97ea872ece730aed82664c424eb4c8291e1ff2480247ccf7409044bc6479f"
 
+[[package]]
+name = "memoffset"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d61c719bcfbcf5d62b3a09efa6088de8c54bc0bfcd3ea7ae39fcc186108b8de1"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fac9e2da13b5eb447a6ce3d392f23a29d8694bff781bf03a16cd9ac8697593b"
+dependencies = [
+ "hermit-abi 0.2.6",
+ "libc",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.17.1"
@@ -217,6 +307,28 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1d2df5196e37bcc87abebc0053e20787d73847bb33134a69841207dd0a47f03b"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b8f95bd6966f5c87776639160a66bd8ab9895d9d4ab01ddba9fc60661aebe8d"
+dependencies = [
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-utils",
+ "num_cpus",
+]
+
 [[package]]
 name = "rustix"
 version = "0.37.19"
@@ -231,6 +343,12 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "strsim"
 version = "0.10.0"

test/check-toolchains/Cargo.toml

@@ -8,3 +8,4 @@ edition = "2021"
 [dependencies]
 anyhow = "1.0.71"
 clap = { version = "4.2.7", features = ["derive"] }
+rayon = "1.7.0"

test/check-toolchains/src/main.rs

 use anyhow::{anyhow, Context};
 use clap::Parser;
+use rayon::prelude::*;
 use std::ffi::OsString;
 use std::fs;
 use std::os::unix::prelude::OsStringExt;
@@ -130,7 +131,7 @@ fn main() -> Result<(), &'static str> {
 
     let failures: Vec<_> = args
         .toolchains
-        .iter()
+        .par_iter()
         .map(|toolchain| (toolchain, check(toolchain, &args.project)))
         .filter_map(|x| {
             if let Err(problem) = x.1 {