Test support for bfloat16 using ml_dtypes.

Author: adamreichold

.github/workflows/ci.yml

@@ -67,7 +67,7 @@ jobs:
         shell: python
       - name: Test
         run: |
-            pip install numpy
+            pip install numpy ml_dtypes
             cargo test --all-features
         # Not on PyPy, because no embedding API
         if: ${{ !startsWith(matrix.python-version, 'pypy') }}
@@ -101,7 +101,7 @@ jobs:
         continue-on-error: true
       - uses: taiki-e/install-action@valgrind
       - run: |
-            pip install numpy
+            pip install numpy ml_dtypes
             cargo test --all-features --release
         env:
           CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER: valgrind --leak-check=no --error-exitcode=1
@@ -115,7 +115,7 @@ jobs:
       - uses: Swatinem/rust-cache@v2
         continue-on-error: true
       - run: |
-            pip install numpy
+            pip install numpy ml_dtypes
             cargo install --locked cargo-careful
             cargo careful test --all-features
 
@@ -201,7 +201,7 @@ jobs:
           python-version: 3.9
           architecture: x64
       - name: Install numpy
-        run: pip install numpy
+        run: pip install numpy ml_dtypes
       - uses: Swatinem/rust-cache@v2
         continue-on-error: true
       - uses: dtolnay/rust-toolchain@stable

tests/array.rs

@@ -1,7 +1,7 @@
 use std::mem::size_of;
 
 #[cfg(feature = "half")]
-use half::f16;
+use half::{bf16, f16};
 use ndarray::{array, s, Array1, Dim};
 use numpy::{
     dtype, get_array_module, npyffi::NPY_ORDER, pyarray, PyArray, PyArray1, PyArray2, PyArrayDescr,
@@ -527,7 +527,7 @@ fn reshape() {
 
 #[cfg(feature = "half")]
 #[test]
-fn half_works() {
+fn half_f16_works() {
     Python::with_gil(|py| {
         let np = py.eval("__import__('numpy')", None, None).unwrap();
         let locals = [("np", np)].into_py_dict(py);
@@ -558,7 +558,48 @@ fn half_works() {
         py_run!(
             py,
             array np,
-            "np.testing.assert_array_almost_equal(array, np.array([[2, 4], [6, 8]], dtype='float16'))"
+            "assert np.all(array == np.array([[2, 4], [6, 8]], dtype='float16'))"
+        );
+    });
+}
+
+#[cfg(feature = "half")]
+#[test]
+fn half_bf16_works() {
+    Python::with_gil(|py| {
+        let np = py.eval("__import__('numpy')", None, None).unwrap();
+        // NumPy itself does not provide a `bfloat16` dtype itself,
+        // so we import ml_dtypes which does register such a dtype.
+        let mldt = py.eval("__import__('ml_dtypes')", None, None).unwrap();
+        let locals = [("np", np), ("mldt", mldt)].into_py_dict(py);
+
+        let array = py
+            .eval(
+                "np.array([[1, 2], [3, 4]], dtype='bfloat16')",
+                None,
+                Some(locals),
+            )
+            .unwrap()
+            .downcast::<PyArray2<bf16>>()
+            .unwrap();
+
+        assert_eq!(
+            array.readonly().as_array(),
+            array![
+                [bf16::from_f32(1.0), bf16::from_f32(2.0)],
+                [bf16::from_f32(3.0), bf16::from_f32(4.0)]
+            ]
+        );
+
+        array
+            .readwrite()
+            .as_array_mut()
+            .map_inplace(|value| *value *= bf16::from_f32(2.0));
+
+        py_run!(
+            py,
+            array np,
+            "assert np.all(array == np.array([[2, 4], [6, 8]], dtype='bfloat16'))"
         );
     });
 }