mlx/python/src/utils.cpp

#include "mlx/utils.h"
#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
#include <optional>

namespace py = pybind11;
using namespace py::literals;
using namespace mlx::core;

// Slightly different from the original, with python context on init we are not
// in the context yet. Only create the inner context on enter then delete on
// exit.
class PyStreamContext {
 public:
  PyStreamContext(StreamOrDevice s) : _inner(nullptr) {
    if (std::holds_alternative<std::monostate>(s)) {
      throw std::runtime_error(
          "[StreamContext] Invalid argument, please specify a stream or device.");
    }
    _s = s;
  }

  void enter() {
    _inner = new StreamContext(_s);
  }

  void exit() {
    if (_inner != nullptr) {
      delete _inner;
      _inner = nullptr;
    }
  }

 private:
  StreamOrDevice _s;
  StreamContext* _inner;
};

void init_utils(py::module_& m) {
  py::class_<PyStreamContext>(m, "StreamContext", R"pbdoc(
        A context manager for setting the current device and stream.

        See :func:`stream` for usage.

        Args:
            s: The stream or device to set as the default.
  )pbdoc")
      .def(py::init<StreamOrDevice>(), "s"_a)
      .def("__enter__", [](PyStreamContext& scm) { scm.enter(); })
      .def(
          "__exit__",
          [](PyStreamContext& scm,
             const std::optional<py::type>& exc_type,
             const std::optional<py::object>& exc_value,
             const std::optional<py::object>& traceback) { scm.exit(); });
  m.def(
      "stream",
      [](StreamOrDevice s) { return PyStreamContext(s); },
      "s"_a,
      R"pbdoc(
        Create a context manager to set the default device and stream.

        Args:
            s: The :obj:`Stream` or :obj:`Device` to set as the default.

        Returns:
            A context manager that sets the default device and stream.

        Example:

        .. code-block::python

          import mlx.core as mx

          # Create a context manager for the default device and stream.
          with mx.stream(mx.cpu):
              # Operations here will use mx.cpu by default.
              pass
      )pbdoc");
}