Kick out py_shared_ptr and instead keep the python instance alive man…

…ually by holding a reference to it

See pybind/pybind11#1389 for why py_shared_ptr was needed in the first place, and the comment from May 27 why we may not want to use it (reference cycle)

src/simsopt/field/magneticfieldclasses.py

@@ -489,6 +489,7 @@ def __init__(self, field, degree, rrange, phirange, zrange, extrapolate=True, nf
             logger.warning(fr"Sure about phirange[1]={phirange[1]}? When exploiting rotational symmetry, the interpolant is never evaluated for phi>2\pi/nfp.")
 
         sopp.InterpolatedField.__init__(self, field, degree, rrange, phirange, zrange, extrapolate, nfp, stellsym)
+        self.__field == field
 
     def to_vtk(self, filename, h=0.1):
         """Export the field evaluated on a regular grid for visualisation with e.g. Paraview."""

src/simsoptpp/python.cpp

@@ -1,8 +1,6 @@
 #include "pybind11/pybind11.h"
 #include "pybind11/stl.h"
 #include "pybind11/functional.h"
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 #define FORCE_IMPORT_ARRAY
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;

src/simsoptpp/python_curves.cpp

@@ -2,10 +2,9 @@
 #include "pybind11/stl.h"
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 
+namespace py = pybind11;
 
 #include "curve.h"
 #include "pycurve.h"
@@ -90,16 +89,16 @@ template <typename T, typename S> void register_common_curve_methods(S &c) {
 }
 
 void init_curves(py::module_ &m) {
-    auto pycurve = py::class_<PyCurve, py_shared_ptr<PyCurve>, PyCurveTrampoline<PyCurve>>(m, "Curve")
+    auto pycurve = py::class_<PyCurve, shared_ptr<PyCurve>, PyCurveTrampoline<PyCurve>>(m, "Curve")
         .def(py::init<vector<double>>());
     register_common_curve_methods<PyCurve>(pycurve);
 
-    auto pycurvexyzfourier = py::class_<PyCurveXYZFourier, py_shared_ptr<PyCurveXYZFourier>, PyCurveXYZFourierTrampoline<PyCurveXYZFourier>, PyCurve>(m, "CurveXYZFourier")
+    auto pycurvexyzfourier = py::class_<PyCurveXYZFourier, shared_ptr<PyCurveXYZFourier>, PyCurveXYZFourierTrampoline<PyCurveXYZFourier>, PyCurve>(m, "CurveXYZFourier")
         .def(py::init<vector<double>, int>())
         .def_readonly("dofs", &PyCurveXYZFourier::dofs);
     register_common_curve_methods<PyCurveXYZFourier>(pycurvexyzfourier);
 
-    auto pycurverzfourier = py::class_<PyCurveRZFourier, py_shared_ptr<PyCurveRZFourier>, PyCurveRZFourierTrampoline<PyCurveRZFourier>, PyCurve>(m, "CurveRZFourier")
+    auto pycurverzfourier = py::class_<PyCurveRZFourier, shared_ptr<PyCurveRZFourier>, PyCurveRZFourierTrampoline<PyCurveRZFourier>, PyCurve>(m, "CurveRZFourier")
         //.def(py::init<int, int>())
         .def(py::init<vector<double>, int, int, bool>())
         .def_readwrite("rc", &PyCurveRZFourier::rc)

src/simsoptpp/python_magneticfield.cpp

@@ -5,11 +5,10 @@
 #include "xtensor-python/pytensor.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
 typedef xt::pytensor<double, 2, xt::layout_type::row_major> PyTensor;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 using std::vector;
 
+namespace py = pybind11;
 #include "magneticfield.h"
 #include "magneticfield_biotsavart.h"
 #include "magneticfield_interpolated.h"
@@ -54,17 +53,17 @@ template <typename T, typename S> void register_common_field_methods(S &c) {
 
 void init_magneticfields(py::module_ &m){
 
-    py::class_<InterpolationRule, py_shared_ptr<InterpolationRule>>(m, "InterpolationRule", "Abstract class for interpolation rules on an interval.")
+    py::class_<InterpolationRule, shared_ptr<InterpolationRule>>(m, "InterpolationRule", "Abstract class for interpolation rules on an interval.")
         .def_readonly("degree", &InterpolationRule::degree, "The degree of the polynomial. The number of interpolation points in `degree+1`.");
 
-    py::class_<UniformInterpolationRule, py_shared_ptr<UniformInterpolationRule>, InterpolationRule>(m, "UniformInterpolationRule", "Polynomial interpolation using equispaced points.")
+    py::class_<UniformInterpolationRule, shared_ptr<UniformInterpolationRule>, InterpolationRule>(m, "UniformInterpolationRule", "Polynomial interpolation using equispaced points.")
         .def(py::init<int>())
         .def_readonly("degree", &UniformInterpolationRule::degree, "The degree of the polynomial. The number of interpolation points in `degree+1`.");
-    py::class_<ChebyshevInterpolationRule, py_shared_ptr<ChebyshevInterpolationRule>, InterpolationRule>(m, "ChebyshevInterpolationRule", "Polynomial interpolation using chebychev points.")
+    py::class_<ChebyshevInterpolationRule, shared_ptr<ChebyshevInterpolationRule>, InterpolationRule>(m, "ChebyshevInterpolationRule", "Polynomial interpolation using chebychev points.")
         .def(py::init<int>())
         .def_readonly("degree", &ChebyshevInterpolationRule::degree, "The degree of the polynomial. The number of interpolation points in `degree+1`.");
 
-    py::class_<RegularGridInterpolant3D<PyTensor>, py_shared_ptr<RegularGridInterpolant3D<PyTensor>>>(m, "RegularGridInterpolant3D",
+    py::class_<RegularGridInterpolant3D<PyTensor>, shared_ptr<RegularGridInterpolant3D<PyTensor>>>(m, "RegularGridInterpolant3D",
             R"pbdoc(
             Interpolates a (vector valued) function on a uniform grid. 
             This interpolant is optimized for fast function evaluation (at the cost of memory usage). The main purpose of this class is to be used to interpolate magnetic fields and then use the interpolant for tasks such as fieldline or particle tracing for which the field needs to be evaluated many many times.
@@ -93,20 +92,20 @@ void init_magneticfields(py::module_ &m){
         .def_readonly("curve", &Coil<PyArray>::curve, "Get the underlying curve.")
         .def_readonly("current", &Coil<PyArray>::current, "Get the underlying current.");
 
-    auto mf = py::class_<PyMagneticField, PyMagneticFieldTrampoline<PyMagneticField>, py_shared_ptr<PyMagneticField>>(m, "MagneticField", "Abstract class representing magnetic fields.")
+    auto mf = py::class_<PyMagneticField, PyMagneticFieldTrampoline<PyMagneticField>, shared_ptr<PyMagneticField>>(m, "MagneticField", "Abstract class representing magnetic fields.")
         .def(py::init<>());
     register_common_field_methods<PyMagneticField>(mf);
         //.def("B", py::overload_cast<>(&PyMagneticField::B));
 
-    auto bs = py::class_<PyBiotSavart, PyMagneticFieldTrampoline<PyBiotSavart>, py_shared_ptr<PyBiotSavart>, PyMagneticField>(m, "BiotSavart")
+    auto bs = py::class_<PyBiotSavart, PyMagneticFieldTrampoline<PyBiotSavart>, shared_ptr<PyBiotSavart>, PyMagneticField>(m, "BiotSavart")
         .def(py::init<vector<shared_ptr<Coil<PyArray>>>>())
         .def("compute", &PyBiotSavart::compute)
         .def("fieldcache_get_or_create", &PyBiotSavart::fieldcache_get_or_create)
         .def("fieldcache_get_status", &PyBiotSavart::fieldcache_get_status)
         .def_readonly("coils", &PyBiotSavart::coils);
     register_common_field_methods<PyBiotSavart>(bs);
 
-    auto ifield = py::class_<PyInterpolatedField, py_shared_ptr<PyInterpolatedField>, PyMagneticField>(m, "InterpolatedField")
+    auto ifield = py::class_<PyInterpolatedField, shared_ptr<PyInterpolatedField>, PyMagneticField>(m, "InterpolatedField")
         .def(py::init<shared_ptr<PyMagneticField>, InterpolationRule, RangeTriplet, RangeTriplet, RangeTriplet, bool, int, bool>())
         .def(py::init<shared_ptr<PyMagneticField>, int, RangeTriplet, RangeTriplet, RangeTriplet, bool, int, bool>())
         .def("estimate_error_B", &PyInterpolatedField::estimate_error_B)

src/simsoptpp/python_surfaces.cpp

@@ -2,11 +2,10 @@
 #include "pybind11/stl.h"
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 using std::vector;
 
+namespace py = pybind11;
 #include "pycurve.h"
 #include "surface.h"
 #include "pysurface.h"

src/simsoptpp/python_tracing.cpp

@@ -1,12 +1,11 @@
 #include "pybind11/pybind11.h"
 #include "pybind11/stl.h"
 #include "pybind11/functional.h"
+namespace py = pybind11;
 #include "xtensor-python/pyarray.hpp"     // Numpy bindings
 typedef xt::pyarray<double> PyArray;
 #include "xtensor-python/pytensor.hpp"     // Numpy bindings
 typedef xt::pytensor<double, 2, xt::layout_type::row_major> PyTensor;
-#include "py_shared_ptr.h"
-PYBIND11_DECLARE_HOLDER_TYPE(T, py_shared_ptr<T>);
 using std::shared_ptr;
 using std::vector;
 #include "tracing.h"