Add support for Eigen::Ref<...> function arguments
Eigen::Ref is a common way to pass eigen dense types without needing a
template, e.g. the single definition `void
func(Eigen::Ref<Eigen::MatrixXd> x)` can be called with any double
matrix-like object.
The current pybind11 eigen support fails with internal errors if
attempting to bind a function with an Eigen::Ref<...> argument because
Eigen::Ref<...> satisfies the "is_eigen_dense" requirement, but can't
compile if actually used: Eigen::Ref<...> itself is not default
constructible, and so the argument std::tuple containing an
Eigen::Ref<...> isn't constructible, which results in compilation
failure.
This commit adds support for Eigen::Ref<...> by giving it its own
type_caster implementation which consists of an internal type_caster of
the referenced type, load/cast methods that dispatch to the internal
type_caster, and a unique_ptr to an Eigen::Ref<> instance that gets
set during load().
There is, of course, no performance advantage for pybind11-using code of
using Eigen::Ref<...>--we are allocating a matrix of the derived type
when loading it--but this has the advantage of allowing pybind11 to bind
transparently to C++ methods taking Eigen::Refs.
diff --git a/example/eigen.cpp b/example/eigen.cpp
index f99ae3a..728b575 100644
--- a/example/eigen.cpp
+++ b/example/eigen.cpp
@@ -9,6 +9,7 @@
#include "example.h"
#include <pybind11/eigen.h>
+#include <Eigen/Cholesky>
Eigen::VectorXf double_col(const Eigen::VectorXf& x)
{ return 2.0f * x; }
@@ -19,6 +20,14 @@
Eigen::MatrixXf double_mat_cm(const Eigen::MatrixXf& x)
{ return 2.0f * x; }
+// Different ways of passing via Eigen::Ref; the first and second are the Eigen-recommended
+Eigen::MatrixXd cholesky1(Eigen::Ref<Eigen::MatrixXd> &x) { return x.llt().matrixL(); }
+Eigen::MatrixXd cholesky2(const Eigen::Ref<const Eigen::MatrixXd> &x) { return x.llt().matrixL(); }
+Eigen::MatrixXd cholesky3(const Eigen::Ref<Eigen::MatrixXd> &x) { return x.llt().matrixL(); }
+Eigen::MatrixXd cholesky4(Eigen::Ref<const Eigen::MatrixXd> &x) { return x.llt().matrixL(); }
+Eigen::MatrixXd cholesky5(Eigen::Ref<Eigen::MatrixXd> x) { return x.llt().matrixL(); }
+Eigen::MatrixXd cholesky6(Eigen::Ref<const Eigen::MatrixXd> x) { return x.llt().matrixL(); }
+
typedef Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor> MatrixXfRowMajor;
MatrixXfRowMajor double_mat_rm(const MatrixXfRowMajor& x)
{ return 2.0f * x; }
@@ -40,6 +49,12 @@
m.def("double_row", &double_row);
m.def("double_mat_cm", &double_mat_cm);
m.def("double_mat_rm", &double_mat_rm);
+ m.def("cholesky1", &cholesky1);
+ m.def("cholesky2", &cholesky2);
+ m.def("cholesky3", &cholesky3);
+ m.def("cholesky4", &cholesky4);
+ m.def("cholesky5", &cholesky5);
+ m.def("cholesky6", &cholesky6);
m.def("fixed_r", [mat]() -> FixedMatrixR {
return FixedMatrixR(mat);
diff --git a/example/eigen.py b/example/eigen.py
index e69605d..6cdc394 100644
--- a/example/eigen.py
+++ b/example/eigen.py
@@ -11,6 +11,7 @@
from example import sparse_passthrough_r, sparse_passthrough_c
from example import double_row, double_col
from example import double_mat_cm, double_mat_rm
+from example import cholesky1, cholesky2, cholesky3, cholesky4, cholesky5, cholesky6
try:
import numpy as np
import scipy
@@ -70,3 +71,10 @@
for slice_idx, ref_mat in enumerate(slices):
print("double_mat_cm(%d) = %s" % (slice_idx, check_got_vs_ref(double_mat_cm(ref_mat), 2.0 * ref_mat)))
print("double_mat_rm(%d) = %s" % (slice_idx, check_got_vs_ref(double_mat_rm(ref_mat), 2.0 * ref_mat)))
+
+i = 1
+for chol in [cholesky1, cholesky2, cholesky3, cholesky4, cholesky5, cholesky6]:
+ mymat = chol(np.array([[1,2,4], [2,13,23], [4,23,77]]))
+ print("cholesky" + str(i) + " " + ("OK" if (mymat == np.array([[1,0,0], [2,3,0], [4,5,6]])).all() else "NOT OKAY"))
+ i += 1
+
diff --git a/example/eigen.ref b/example/eigen.ref
index 03091cc..93e88ad 100644
--- a/example/eigen.ref
+++ b/example/eigen.ref
@@ -27,3 +27,9 @@
double_mat_rm(1) = OK
double_mat_cm(2) = OK
double_mat_rm(2) = OK
+cholesky1 OK
+cholesky2 OK
+cholesky3 OK
+cholesky4 OK
+cholesky5 OK
+cholesky6 OK