First step towards safely creating universal functions in Rust.

Author: adamreichold

src/dtype.rs

@@ -402,6 +402,11 @@ pub unsafe trait Element: Clone + Send {
 
     /// Returns the associated type descriptor ("dtype") for the given element type.
     fn get_dtype<'py>(py: Python<'py>) -> &'py PyArrayDescr;
+
+    /// TODO
+    fn get_npy_type() -> Option<NPY_TYPES> {
+        None
+    }
 }
 
 fn npy_int_type_lookup<T, T0, T1, T2>(npy_types: [NPY_TYPES; 3]) -> NPY_TYPES {
@@ -458,6 +463,10 @@ macro_rules! impl_element_scalar {
             fn get_dtype<'py>(py: Python<'py>) -> &'py PyArrayDescr {
                 PyArrayDescr::from_npy_type(py, $npy_type)
             }
+
+            fn get_npy_type() -> Option<NPY_TYPES> {
+                Some($npy_type)
+            }
         }
     };
     ($ty:ty => $npy_type:ident $(,#[$meta:meta])*) => {

src/lib.rs

@@ -83,6 +83,7 @@ pub mod npyffi;
 mod slice_container;
 mod strings;
 mod sum_products;
+pub mod ufunc;
 mod untyped_array;
 
 pub use ndarray;

src/npyffi/flags.rs

@@ -81,3 +81,10 @@ pub const NPY_OBJECT_DTYPE_FLAGS: npy_char = NPY_LIST_PICKLE
     | NPY_ITEM_REFCOUNT
     | NPY_NEEDS_INIT
     | NPY_NEEDS_PYAPI;
+
+pub const NPY_UFUNC_ZERO: c_int = 0;
+pub const NPY_UFUNC_ONE: c_int = 1;
+pub const NPY_UFUNC_MINUS_ONE: c_int = 2;
+pub const NPY_UFUNC_NONE: c_int = -1;
+pub const NPY_UFUNC_REORDERABLE_NONE: c_int = -2;
+pub const NPY_UFUNC_IDENTITY_VALUE: c_int = -3;

src/ufunc.rs

@@ -0,0 +1,246 @@
+//! TODO
+
+use std::ffi::CString;
+use std::mem::{size_of, MaybeUninit};
+use std::os::raw::{c_char, c_int, c_void};
+use std::ptr::null_mut;
+
+use ndarray::{ArrayView1, ArrayViewMut1, Axis, Dim, Ix1, ShapeBuilder, StrideShape};
+use pyo3::{PyAny, PyResult, Python};
+
+use crate::{
+    dtype::Element,
+    npyffi::{flags, npy_intp, objects::PyUFuncGenericFunction, ufunc::PY_UFUNC_API},
+};
+
+/// TODO
+#[repr(i32)]
+#[derive(Debug)]
+pub enum Identity {
+    /// UFunc has unit of 0, and the order of operations can be reordered
+    /// This case allows reduction with multiple axes at once.
+    Zero = flags::NPY_UFUNC_ZERO,
+    /// UFunc has unit of 1, and the order of operations can be reordered
+    /// This case allows reduction with multiple axes at once.
+    One = flags::NPY_UFUNC_ONE,
+    /// UFunc has unit of -1, and the order of operations can be reordered
+    /// This case allows reduction with multiple axes at once. Intended for bitwise_and reduction.
+    MinusOne = flags::NPY_UFUNC_MINUS_ONE,
+    /// UFunc has no unit, and the order of operations cannot be reordered.
+    /// This case does not allow reduction with multiple axes at once.
+    None = flags::NPY_UFUNC_NONE,
+    /// UFunc has no unit, and the order of operations can be reordered
+    /// This case allows reduction with multiple axes at once.
+    ReorderableNone = flags::NPY_UFUNC_REORDERABLE_NONE,
+    /// UFunc unit is an identity_value, and the order of operations can be reordered
+    /// This case allows reduction with multiple axes at once.
+    IdentityValue = flags::NPY_UFUNC_IDENTITY_VALUE,
+}
+
+/// TODO
+///
+/// ```
+/// # #![allow(mixed_script_confusables)]
+/// # use std::ffi::CString;
+/// #
+/// use pyo3::{py_run, Python};
+/// use ndarray::{azip, ArrayView1, ArrayViewMut1};
+/// use numpy::ufunc::{from_func, Identity};
+///
+/// Python::with_gil(|py| {
+///    let logit = |[p]: [ArrayView1<'_, f64>; 1], [α]: [ArrayViewMut1<'_, f64>; 1]| {
+///        azip!((p in p, α in α) {
+///            let mut tmp = *p;
+///            tmp /= 1.0 - tmp;
+///            *α = tmp.ln();
+///        });
+///    };
+///
+///    let logit =
+///        from_func(py, CString::new("logit").unwrap(), Identity::None, logit).unwrap();
+///
+///    py_run!(py, logit, "assert logit(0.5) == 0.0");
+///
+///    let np = py.import("numpy").unwrap();
+///
+///    py_run!(py, logit np, "assert (logit(np.full(100, 0.5)) == np.zeros(100)).all()");
+/// });
+/// ```
+///
+/// ```
+/// # #![allow(mixed_script_confusables)]
+/// # use std::ffi::CString;
+/// #
+/// use pyo3::{py_run, Python};
+/// use ndarray::{azip, ArrayView1, ArrayViewMut1};
+/// use numpy::ufunc::{from_func, Identity};
+///
+/// Python::with_gil(|py| {
+///     let cart_to_polar = |[x, y]: [ArrayView1<'_, f64>; 2], [r, φ]: [ArrayViewMut1<'_, f64>; 2]| {
+///         azip!((&x in x, &y in y, r in r, φ in φ) {
+///             *r = f64::hypot(x, y);
+///             *φ = f64::atan2(x, y);
+///         });
+///     };
+///
+///     let cart_to_polar = from_func(
+///         py,
+///         CString::new("cart_to_polar").unwrap(),
+///         Identity::None,
+///         cart_to_polar,
+///     )
+///     .unwrap();
+///
+///     let np = py.import("numpy").unwrap();
+///
+///     py_run!(py, cart_to_polar np, "np.testing.assert_array_almost_equal(cart_to_polar(3.0, 4.0), (5.0, 0.643501))");
+///
+///     py_run!(py, cart_to_polar np, "np.testing.assert_array_almost_equal(cart_to_polar(np.full((10, 10), 3.0), np.full((10, 10), 4.0))[0], np.full((10, 10), 5.0))");
+///     py_run!(py, cart_to_polar np, "np.testing.assert_array_almost_equal(cart_to_polar(np.full((10, 10), 3.0), np.full((10, 10), 4.0))[1], np.full((10, 10), 0.643501))");
+/// });
+/// ```
+pub fn from_func<'py, T, F, const NIN: usize, const NOUT: usize>(
+    py: Python<'py>,
+    name: CString,
+    identity: Identity,
+    func: F,
+) -> PyResult<&'py PyAny>
+where
+    T: Element,
+    F: Fn([ArrayView1<'_, T>; NIN], [ArrayViewMut1<'_, T>; NOUT]) + 'static,
+{
+    let wrap_func = [Some(wrap_func::<T, F, NIN, NOUT> as _)];
+
+    let r#type = T::get_npy_type().expect("universal function only work for built-in types");
+
+    let inputs = [r#type as _; NIN];
+    let outputs = [r#type as _; NOUT];
+
+    let data = Data {
+        func,
+        wrap_func,
+        name,
+        inputs,
+        outputs,
+    };
+
+    let data = Box::leak(Box::new(data));
+
+    unsafe {
+        py.from_owned_ptr_or_err(PY_UFUNC_API.PyUFunc_FromFuncAndData(
+            py,
+            data.wrap_func.as_mut_ptr(),
+            data as *mut Data<F, NIN, NOUT> as *mut c_void as *mut *mut c_void,
+            data.inputs.as_mut_ptr(),
+            /* ntypes = */ 1,
+            NIN as c_int,
+            NOUT as c_int,
+            identity as c_int,
+            data.name.as_ptr(),
+            /* doc = */ null_mut(),
+            /* unused = */ 0,
+        ))
+    }
+}
+
+#[repr(C)]
+struct Data<F, const NIN: usize, const NOUT: usize> {
+    func: F,
+    wrap_func: [PyUFuncGenericFunction; 1],
+    name: CString,
+    inputs: [c_char; NIN],
+    outputs: [c_char; NOUT],
+}
+
+unsafe extern "C" fn wrap_func<T, F, const NIN: usize, const NOUT: usize>(
+    args: *mut *mut c_char,
+    dims: *mut npy_intp,
+    steps: *mut npy_intp,
+    data: *mut c_void,
+) where
+    F: Fn([ArrayView1<'_, T>; NIN], [ArrayViewMut1<'_, T>; NOUT]),
+{
+    // TODO: Check aliasing requirements using the `borrow` module.
+
+    let mut inputs = MaybeUninit::<[ArrayView1<'_, T>; NIN]>::uninit();
+    let inputs_ptr = inputs.as_mut_ptr() as *mut ArrayView1<'_, T>;
+
+    for i in 0..NIN {
+        let (ptr, shape, invert) = unpack_arg(args, dims, steps, i);
+
+        let mut input = ArrayView1::from_shape_ptr(shape, ptr);
+        if invert {
+            input.invert_axis(Axis(0));
+        }
+        inputs_ptr.add(i).write(input);
+    }
+
+    let mut outputs = MaybeUninit::<[ArrayViewMut1<'_, T>; NOUT]>::uninit();
+    let outputs_ptr = outputs.as_mut_ptr() as *mut ArrayViewMut1<'_, T>;
+
+    for i in 0..NOUT {
+        let (ptr, shape, invert) = unpack_arg(args, dims, steps, NIN + i);
+
+        let mut output = ArrayViewMut1::from_shape_ptr(shape, ptr);
+        if invert {
+            output.invert_axis(Axis(0));
+        }
+        outputs_ptr.add(i).write(output);
+    }
+
+    let data = &*(data as *mut Data<F, NIN, NOUT>);
+    (data.func)(inputs.assume_init(), outputs.assume_init());
+}
+
+unsafe fn unpack_arg<T>(
+    args: *mut *mut c_char,
+    dims: *mut npy_intp,
+    steps: *mut npy_intp,
+    i: usize,
+) -> (*mut T, StrideShape<Ix1>, bool) {
+    let dim = Dim([*dims as usize]);
+    let itemsize = size_of::<T>();
+
+    let mut ptr = *args.add(i);
+    let mut invert = false;
+
+    let step = *steps.add(i);
+
+    let step = if step >= 0 {
+        Dim([step as usize / itemsize])
+    } else {
+        ptr = ptr.offset(step * (*dims - 1));
+        invert = true;
+
+        Dim([(-step) as usize / itemsize])
+    };
+
+    (ptr as *mut T, dim.strides(step), invert)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use ndarray::azip;
+    use pyo3::py_run;
+
+    #[test]
+    fn from_func_handles_negative_strides() {
+        Python::with_gil(|py| {
+            let negate = from_func(
+                py,
+                CString::new("negate").unwrap(),
+                Identity::None,
+                |[x]: [ArrayView1<'_, f64>; 1], [y]: [ArrayViewMut1<'_, f64>; 1]| {
+                    azip!((x in x, y in y) *y = -x);
+                },
+            )
+            .unwrap();
+
+            let np = py.import("numpy").unwrap();
+
+            py_run!(py, negate np, "assert (negate(np.linspace(1.0, 10.0, 10)[::-1]) == np.linspace(-10.0, -1.0, 10)).all()");
+        });
+    }
+}