Add experimental Rust backend adapter

.github/workflows/CI.yml

@@ -110,6 +110,33 @@ jobs:
       - name: "Run development test"
         run: PYSR_TEST_JULIA_VERSION=${{ matrix.julia-version }} PYSR_TEST_PYTHON_VERSION=${{ matrix.python-version }} python -m pysr test dev
 
+  rust_backend_adapter:
+    name: Test Rust backend adapter
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        shell: bash
+    strategy:
+      matrix:
+        python-version: ['3.13']
+
+    steps:
+      - uses: actions/checkout@v6
+      - name: "Set up Python"
+        uses: actions/setup-python@v6
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: pip
+      - name: "Install PySR test dependencies"
+        run: |
+            python -m pip install --upgrade pip
+            pip install -e .
+            python -m pip install pytest
+      - name: "Assert default import is Julia-free"
+        run: python -c "import sys; import pysr; assert 'juliacall' not in sys.modules; from pysr import PySRRegressor; assert PySRRegressor().backend == 'auto'"
+      - name: "Run Rust backend adapter tests"
+        run: python -m pysr test rust
+
   conda_test:
     runs-on: ${{ matrix.os }}
     defaults:

README.md

@@ -73,7 +73,27 @@ You can install PySR with pip:
 pip install pysr
 ```
 
-Julia dependencies will be installed at first import.
+If you plan to use the experimental Rust adapter, select the Rust dependency at install time:
+
+```bash
+pip install "pysr[rust]"
+```
+
+Julia dependencies will be installed when the Julia backend is used.
+
+PySR also includes an experimental runtime switch for the Rust adapter:
+
+```python
+PySRRegressor(backend="rust")
+```
+
+The Rust backend adapter expects the optional `symbolic_regression_rs` Python
+module from the `pysr-rust-backend` package. It is installed automatically by
+the `rust` extra.
+
+The default `backend="auto"` uses the Rust backend when `pysr-rust-backend` is
+installed and falls back to Julia otherwise. Set `backend="julia"` to force the
+full-featured and supported Julia backend.
 
 ### Conda
 

benchmarks/README.md

@@ -1,5 +1,24 @@
 # Benchmark 1
 
+## Backend comparison
+
+To compare the experimental Rust backend against the default Julia backend on
+the same generated dataset, run:
+
+```bash
+python benchmarks/compare_backends.py --niterations 3 --repeats 3
+```
+
+Use `--mode subprocess` to run each trial in a fresh Python process, which is
+useful when measuring startup-heavy workflows:
+
+```bash
+python benchmarks/compare_backends.py --mode subprocess --niterations 1 --repeats 3
+```
+
+The script reports wall-clock timing plus the best loss, prediction MSE, and
+selected equation for each backend.
+
 The following benchmarks were ran with this command on a node on CCA's BNL cluster (40-cores). At no time was the node fully busy. The tags were put into the file `tags.txt`, and the `benchmark.sh` was copied to the root folder. This is the command used:
 
 ```bash