feat: Add pumpkin_solver solver

.github/workflows/rust.yml

@@ -154,6 +154,19 @@ jobs:
       - name: Run tests with Clarabel on WASM
         run: wasm-pack test --node --no-default-features --features clarabel
 
+  test-pumpkin-solver:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - name: install deps
+        run: NO_CPLEX=true ./build/setup.sh
+      - name: Build pumpkin-solver
+        run: cargo build --features pumpkin-solver --tests
+      - name: Run tests with pumpkin-solver
+        run: cargo test --no-default-features --features pumpkin-solver
+
   bench:
     runs-on: ubuntu-latest
     steps:

Cargo.toml

@@ -31,6 +31,7 @@ all_default_solvers = [
     "scip_bundled",
     "lp-solvers",
     "clarabel",
+    "pumpkin-solver",
 ] # cplex-rs is not included because it is incompatible with lpsolve
 minilp = [
     "microlp",
@@ -45,6 +46,7 @@ russcip = { version = "0.6.4", optional = true }
 lp-solvers = { version = "1.0.0", features = ["cplex"], optional = true }
 cplex-rs = { version = "0.1", optional = true }
 clarabel = { version = "0.10.0", optional = true, features = [] }
+pumpkin-solver = { version = "0.1.4", optional = true }
 fnv = "1.0.5"
 
 [dev-dependencies]
@@ -66,7 +68,7 @@ all-features = false
 # Use almost the same as all_default_solvers. Similarly, cplex-rs is not
 # included because it is incompatible with lpsolve. Additionally,
 # russcip/bundled is not included because network access is blocked on docs.rs.
-features = ["coin_cbc", "microlp", "lpsolve", "highs", "lp-solvers", "clarabel"]
+features = ["coin_cbc", "microlp", "lpsolve", "highs", "lp-solvers", "clarabel", "pumpkin-solver"]
 default-target = "x86_64-unknown-linux-gnu"
 targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = ["--cfg", "docsrs"]

README.md

@@ -69,16 +69,17 @@ You can find a resource allocation problem example in
 This library offers an abstraction over multiple solvers. By default, it uses [cbc][cbc], but
 you can also activate other solvers using cargo features.
 
-| solver feature name    | integer variables | no C compiler\* | no additional libs\*   | fast\* | WASM\* |
-| ---------------------- | ----------------- | --------------- | ---------------------- | ---- | ---- |
-| [`coin_cbc`][cbc]      | ✅                | ✅              | ❌                     | ✅   | ❌   |
-| [`highs`][highs]       | ✅                | ❌              | ✅¹                    | ✅   | ❌   |
-| [`lpsolve`][lpsolve]   | ✅                | ❌              | ✅                     | ❌   | ❌   |
-| [`microlp`][microlp]   | ✅                | ✅              | ✅                     | ❌   | ✅   |
-| [`lp-solvers`][lps]    | ✅                | ✅              | ✅                     | ❌   | ❌   |
-| [`scip`][scip]         | ✅                | ✅              | ✅²                    | ✅   | ❌   |
-| [`cplex-rs`][cplex]    | ✅                | ❌              | ✅³                    | ✅   | ❌   |
-| [`clarabel`][clarabel] | ❌                | ✅              | ✅                     | ✅   | ✅   |
+| solver feature name         | integer variables | no C compiler\* | no additional libs\*   | fast\* | WASM\* |
+| --------------------------- | ----------------- | --------------- | ---------------------- | ---- | ---- |
+| [`coin_cbc`][cbc]           | ✅                | ✅              | ❌                     | ✅   | ❌   |
+| [`highs`][highs]            | ✅                | ❌              | ✅¹                    | ✅   | ❌   |
+| [`lpsolve`][lpsolve]        | ✅                | ❌              | ✅                     | ❌   | ❌   |
+| [`microlp`][microlp]        | ✅                | ✅              | ✅                     | ❌   | ✅   |
+| [`lp-solvers`][lps]         | ✅                | ✅              | ✅                     | ❌   | ❌   |
+| [`scip`][scip]              | ✅                | ✅              | ✅²                    | ✅   | ❌   |
+| [`cplex-rs`][cplex]         | ✅                | ❌              | ✅³                    | ✅   | ❌   |
+| [`clarabel`][clarabel]      | ❌                | ✅              | ✅                     | ✅   | ✅   |
+| [`pumpkin-solver`][pumpkin] | ✅                | ✅              | ✅                     | ✅   | ❌   |
 
 - \* *no C compiler*: builds with only cargo, without requiring you to install a C compiler
 - \* *no additional libs*: works without additional libraries at runtime, all the dependencies are statically linked
@@ -210,6 +211,20 @@ trait, which allows you to access the dual values of the constraints (the shadow
 
 [clarabel]: https://github.com/oxfordcontrol/Clarabel.rs
 
+### [Pumpkin][pumpkin]
+
+Pumpkin is a combinatorial optimization solver based on lazy clause generation.
+It is written in pure Rust and supports integer variables along with several global constraints,
+including cumulative, arithmetic (linear in/equalities, integer division, integer multiplication,
+maximum, absolute value) and clausal constraints.
+
+It produces certificates of unsatisfiability and can be used as both a library and a command-line
+tool, serving also as a MiniZinc backend. Dual licensed under
+[MIT](https://github.com/ConSol-Lab/pumpkin/blob/main/LICENSE-MIT) and
+[Apache-2.0](https://github.com/ConSol-Lab/pumpkin/blob/main/LICENSE-APACHE).
+
+[pumpkin]: https://github.com/ConSol-Lab/pumpkin
+
 ## Variable types
 
 `good_lp` internally represents all [variable](https://docs.rs/good_lp/latest/good_lp/variable/struct.Variable.html) values and coefficients as `f64`.

src/lib.rs

@@ -76,6 +76,7 @@ pub use expression::Expression;
     feature = "highs",
     feature = "scip",
     feature = "cplex-rs",
+    feature = "pumpkin-solver",
 )))]
 #[cfg(feature = "clarabel")]
 pub use solvers::clarabel::clarabel as default_solver;
@@ -120,6 +121,21 @@ pub use solvers::microlp::microlp;
 #[cfg(feature = "microlp")]
 /// When the "coin_cbc" cargo feature is absent, microlp is used as the default solver
 pub use solvers::microlp::microlp as default_solver;
+#[cfg(feature = "pumpkin-solver")]
+#[cfg_attr(docsrs, doc(cfg(feature = "pumpkin-solver")))]
+pub use solvers::pumpkin_solver::pumpkin;
+#[cfg(not(any(
+    feature = "coin_cbc",
+    feature = "microlp",
+    feature = "lpsolve",
+    feature = "highs",
+    feature = "lp-solvers",
+    feature = "scip",
+    feature = "cplex-rs",
+    feature = "clarabel"
+)))]
+#[cfg(feature = "pumpkin-solver")]
+pub use solvers::pumpkin_solver::pumpkin as default_solver;
 #[cfg(feature = "scip")]
 #[cfg_attr(docsrs, doc(cfg(feature = "highs")))]
 pub use solvers::scip::scip;
@@ -161,6 +177,7 @@ pub const default_solver: LpSolver<
     feature = "scip",
     feature = "cplex-rs",
     feature = "clarabel",
+    feature = "pumpkin-solver",
 )))]
 compile_error!(
     "No solver available. \

src/solvers/mod.rs

@@ -41,6 +41,10 @@ pub mod lp_solvers;
 #[cfg_attr(docsrs, doc(cfg(feature = "clarabel")))]
 pub mod clarabel;
 
+#[cfg(feature = "pumpkin-solver")]
+#[cfg_attr(docsrs, doc(cfg(feature = "pumpkin-solver")))]
+pub mod pumpkin_solver;
+
 /// An entity that is able to solve linear problems
 pub trait Solver {
     /// The internal model type used by the solver