Upgrade pybind11 to 2.2+

[qianyizh]

The current pybind11 is modified from 2.0 dev.
The main modifications are:

1. Direct (reference) access of Eigen matrices, using this patch Eigen/numpy referencing pybind/pybind11#610
2. Change of std::vector binding style

The first modification is now merged into pybind11 master branch.
The pybind11 in Open3D should be upgraded to mainstream stable pybind11 version.

[syncle]

I have been spent some spare time for upgrading pybind.
I fixed many issues by referring upgrade to pybind 2.2 except the error below.

/Users/jaesikpa/Research/Open3D/src/Python/py3d_eigen.cpp:90:10: error: no matching constructor for initialization of 'py::buffer_info'
                return py::buffer_info(
                       ^
/Users/jaesikpa/Research/Open3D/src/Python/py3d_eigen.cpp:176:2: note: in instantiation of function template specialization '(anonymous
      namespace)::pybind_eigen_vector_of_vector<Eigen::Matrix<double, 3, 1, 0, 3, 1> >' requested here
        pybind_eigen_vector_of_vector<Eigen::Vector3d>(m, "Vector3dVector",
        ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:28:5: note: candidate constructor not viable: cannot
      convert initializer list argument to 'detail::any_container<ssize_t>' (aka 'any_container<long>')
    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:39:5: note: candidate constructor template not viable:
      requires 3 arguments, but 6 were provided
    buffer_info(T *ptr, detail::any_container<ssize_t> shape_in, detail::any_container<ssize_t> strides_in)
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:46:5: note: candidate constructor template not viable:
      requires 2 arguments, but 6 were provided
    buffer_info(T *ptr, ssize_t size)
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:83:5: note: candidate constructor not viable: requires 7
      arguments, but 6 were provided
    buffer_info(private_ctr_tag, void *ptr, ssize_t itemsize, const std::string &format, ssize_t ndim,
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:42:5: note: candidate constructor not viable: requires 4
      arguments, but 6 were provided
    buffer_info(void *ptr, ssize_t itemsize, const std::string &format, ssize_t size)
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:49:14: note: candidate constructor not viable: requires at
      most 2 arguments, but 6 were provided
    explicit buffer_info(Py_buffer *view, bool ownview = true)
             ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:56:5: note: candidate constructor not viable: requires 1
      argument, but 6 were provided
    buffer_info(const buffer_info &) = delete;
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:59:5: note: candidate constructor not viable: requires
      single argument 'other', but 6 arguments were provided
    buffer_info(buffer_info &&other) {
    ^
/Users/jaesikpa/Research/Open3D/src/External/pybind11/include/pybind11/buffer_info.h:26:5: note: candidate constructor not viable: requires 0
      arguments, but 6 were provided
    buffer_info() { }
    ^
:

The compile error comes from the following lines in src/Python/py3d_eigen.cpp:

	auto vec = py::bind_vector_without_repr<std::vector<EigenVector>>(
			m, bind_name, py::buffer_protocol());
	vec.def_buffer([](std::vector<EigenVector> &v) -> py::buffer_info {
		return py::buffer_info(
				v.data(), sizeof(Scalar),
				py::format_descriptor<Scalar>::format(),
				2, {v.size(), EigenVector::RowsAtCompileTime},
				{sizeof(EigenVector), sizeof(Scalar)});
	});

FYI, the following lines are safe:

	auto vec = py::bind_vector<std::vector<Scalar>>(m, bind_name,
			py::buffer_protocol());
	vec.def_buffer([](std::vector<Scalar> &v) -> py::buffer_info {
		return py::buffer_info(
				v.data(), sizeof(Scalar),
				py::format_descriptor<Scalar>::format(),
				1, {v.size()}, {sizeof(Scalar)});
	});

The only difference is to use py::bind_vector_without_repr() instead of py::bind_vector() made by @qianyizh. @qianyizh: Can you tell me how to resolve this issue?

[qianyizh]

Ah, I remember.

I hated the bind_vector function from pybind11, because its __repr__ prints the complete list of all elements. For example, when you call print(pcd.points) it prints the whole list which can be extremely long.

This is not the behavior I wanted, so I copied the pybind11 convenient function bind_vector but removed the __repr__ part, and called that function bind_vector_without_repr.

Can you check:

1. If pybind11 still have the long list printing __repr__ behavior? If it is fixed, then we just replace all bind_vector_without_repr with bind_vector. The __repr__ part should also be removed from pybind_eigen_vector_of_vector and pybind_eigen_vector_of_matrix.
2. If it is not fixed. Then copy out the body of the new bind_vector function, paste them into bind_vector_without_repr but remove the __repr__ part.

This should resolve the issue.

[syncle]

Good. I am working on this issue.

[syncle]

I decided to keep bind_vector_without_repr. Actually the error comes from converting
{v.size(), EigenVector::RowsAtCompileTime} into detail::any_container<ssize_t>. It is because pybind2.2 has strict compile time error-check.

This fixes the error:

auto vec = py::bind_vector_without_repr<std::vector<EigenVector>>(
			m, bind_name, py::buffer_protocol());
	vec.def_buffer([](std::vector<EigenVector> &v) -> py::buffer_info {
		size_t rows = EigenVector::RowsAtCompileTime;
		return py::buffer_info(
				v.data(), sizeof(Scalar),
				py::format_descriptor<Scalar>::format(),
				2, {v.size(), rows,
				{sizeof(EigenVector), sizeof(Scalar)});
	});

Now everything works fine. I tested pybind2.2 with the tutorial scripts.

[syncle]

The remaining job is to replace ___init___ for classes. It is not critical issue, but highly recommended by pybind2.2 to avoid runtime warnings.

For example, (from pybind upgrade guide)

// old -- deprecated (runtime warning shown only in debug mode)
py::class<Foo>(m, "Foo")
    .def("__init__", [](Foo &self, ...) {
        new (&self) Foo(...); // uses placement-new
    });

// new
py::class<Foo>(m, "Foo")
    .def(py::init([](...) { // Note: no `self` argument
        return new Foo(...); // return by raw pointer
        // or: return std::make_unique<Foo>(...); // return by holder
        // or: return Foo(...); // return by value (move constructor)
    }));

Now I am trying to replace

	pinhole_intr.def("__init__", [](PinholeCameraIntrinsic &c, int w, int h,
			double fx, double fy, double cx, double cy) {
		new (&c)PinholeCameraIntrinsic(w, h, fx, fy, cx, cy);
	}, "width"_a, "height"_a, "fx"_a, "fy"_a, "cx"_a, "cy"_a);

with

	pinhole_intr.def(py::init([](int w, int h,
	 		double fx, double fy, double cx, double cy) {
	 	return new PinholeCameraIntrinsic(w, h, fx, fy, cx, cy);
	}, "width"_a, "height"_a, "fx"_a, "fy"_a, "cx"_a, "cy"_a));

but this makes compile error. It is because of keyword arguments. I can compile it without keyword arguments. @qianyizh do you have any suggestion for this issue?

[qianyizh]

What is a keyword argument?

[syncle]

It is "width"_a, "height"_a, "fx"_a, "fy"_a, "cx"_a, "cy"_a. If I remove this line, it complies.

[qianyizh]

I think they are the decorations to the function, i.e., when you type help(xxx.__init__), these decorations will pop out as the argument names.