From dd566173531b475ff256958662a4875844040190 Mon Sep 17 00:00:00 2001
From: Mossa <cgmossa@gmail.com>
Date: Sun, 24 May 2026 02:04:50 +0200
Subject: [PATCH 1/2] feat: make rayon an optional feature

Both diffsol and diffsol-c now expose a `rayon` cargo feature (in
default) that controls whether `faer/rayon` and, for diffsol,
`diffsl?/rayon` are enabled. Behavior with default features is
unchanged.

This also removes the previously target-gated faer dep declarations
that silently dropped the rayon feature on wasm32; users now turn
rayon off explicitly via `default-features = false`.

In the workspace `diffsl` dep, drop the always-on `rayon` feature so
the per-crate `rayon` feature is authoritative.
---
 Cargo.toml           | 2 +-
 diffsol-c/Cargo.toml | 8 ++++----
 diffsol/Cargo.toml   | 8 ++------
 3 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 4e7a8900..a3c5741c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,7 +21,7 @@ faer = { version = "0.24", default-features = false, features = [
 ] }
 faer-traits = "0.24"
 cudarc = { version = "0.19", default-features = false }
-diffsl = { version = "0.11.9", features = ["rayon"] }
+diffsl = { version = "0.11.9" }
 
 plotly = { version = "0.14" }
 argmin = { version = "0.11.0" }
diff --git a/diffsol-c/Cargo.toml b/diffsol-c/Cargo.toml
index d0c77414..a1626108 100644
--- a/diffsol-c/Cargo.toml
+++ b/diffsol-c/Cargo.toml
@@ -12,8 +12,9 @@ readme = "../README.md"
 crate-type = ["cdylib", "rlib"]
 
 [features]
-default = ["diffsl-external-dynamic"]
+default = ["diffsl-external-dynamic", "rayon"]
 wasm = ["getrandom/js"]
+rayon = ["diffsol/rayon", "faer/rayon"]
 external = []
 external-dynamic = []
 diffsl-external-f64 = [
@@ -43,7 +44,7 @@ suitesparse = ["diffsol/suitesparse"]
 
 [dependencies]
 diffsl = { workspace = true }
-diffsol = { path = "../diffsol", version = "0.14.0", features = ["diffsl"] }
+diffsol = { path = "../diffsol", version = "0.14.0", default-features = false, features = ["nalgebra", "faer", "diffsl"] }
 dlmalloc = { version = "0.2", features = ["global"] }
 nalgebra = { workspace = true, features = ["std"] }
 ndarray = { version = "0.17.2" }
@@ -52,12 +53,11 @@ schemars = "1.1.0"
 serde = { workspace = true }
 serde_json = { workspace = true }
 paste = { workspace = true }
+faer = { workspace = true }
 
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 getrandom = { version = "0.2", features = ["js"] }
-faer = { workspace = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 getrandom = { version = "0.2", optional = true }
-faer = { workspace = true, features = ["rayon"] }
diff --git a/diffsol/Cargo.toml b/diffsol/Cargo.toml
index 7d9a8de7..a97c3b8a 100644
--- a/diffsol/Cargo.toml
+++ b/diffsol/Cargo.toml
@@ -12,9 +12,10 @@ readme = "../README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["nalgebra", "faer"]
+default = ["nalgebra", "faer", "rayon"]
 faer = []
 nalgebra = []
+rayon = ["faer/rayon", "diffsl?/rayon"]
 cuda = ["dep:cudarc"]
 sundials = ["suitesparse_sys", "bindgen", "cc"]
 suitesparse = ["suitesparse_sys"]
@@ -57,11 +58,6 @@ cudarc = { workspace = true, optional = true, default-features = false, features
 ] }
 log = "0.4.29"
 serde_json = { workspace = true }
-
-[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-faer = { workspace = true, features = ["rayon"] }
-
-[target.'cfg(target_arch = "wasm32")'.dependencies]
 faer = { workspace = true }
 
 [dev-dependencies]

From 80370c278c393e9e8439ec9c1c8a42d7b85fed16 Mon Sep 17 00:00:00 2001
From: Mossa <cgmossa@gmail.com>
Date: Sun, 24 May 2026 02:16:21 +0200
Subject: [PATCH 2/2] fix: make rayon opt-in rather than default
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The wasm example pulls diffsol with default features. When `rayon`
was in `default`, the cascade `faer/rayon` → rayon → atomic-wait
broke the wasm32 build because atomic-wait has no `platform` module
for that target.

Drop `rayon` from default in both diffsol and diffsol-c so it must be
enabled explicitly. Matches the original target-gated behavior on
wasm (no rayon) and lets non-wasm consumers also turn it off without
needing `default-features = false`.
---
 diffsol-c/Cargo.toml | 2 +-
 diffsol/Cargo.toml   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/diffsol-c/Cargo.toml b/diffsol-c/Cargo.toml
index a1626108..6cee3e9a 100644
--- a/diffsol-c/Cargo.toml
+++ b/diffsol-c/Cargo.toml
@@ -12,7 +12,7 @@ readme = "../README.md"
 crate-type = ["cdylib", "rlib"]
 
 [features]
-default = ["diffsl-external-dynamic", "rayon"]
+default = ["diffsl-external-dynamic"]
 wasm = ["getrandom/js"]
 rayon = ["diffsol/rayon", "faer/rayon"]
 external = []
diff --git a/diffsol/Cargo.toml b/diffsol/Cargo.toml
index a97c3b8a..7567c265 100644
--- a/diffsol/Cargo.toml
+++ b/diffsol/Cargo.toml
@@ -12,7 +12,7 @@ readme = "../README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["nalgebra", "faer", "rayon"]
+default = ["nalgebra", "faer"]
 faer = []
 nalgebra = []
 rayon = ["faer/rayon", "diffsl?/rayon"]