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[英]How to pass a default numpy array argument to a function in pybind11?
[英]Can I use pybind11 to pass a numpy array to a function accepting a Eigen::Tensor?
我可以使用pybind1
將三維 numpy 數組傳遞給 c++ function 接受Eigen::Tensor
作為參數。 例如,考慮以下 c++ function:
Eigen::Tensor<double, 3> addition_tensor(Eigen::Tensor<double, 3> a,
Eigen::Tensor<double, 3> b) {
return a + b;
}
編譯 function 后,將其導入 python 並傳遞 numpy 數組np.ones((1, 2, 2))
給它,我收到以下錯誤消息:
TypeError: addition_tensor(): incompatible function arguments. The following argument types are supported:
1. (arg0: Eigen::Tensor<double, 3, 0, long>, arg1: Eigen::Tensor<double, 3, 0, long>) -> Eigen::Tensor<double, 3, 0, long>
我特別驚訝於無法傳遞三維 numpy 數組,因為我可以將二維numpy array
傳遞給 function 接受: Eigen::MatrixXd
Eigen::MatrixXd addition(Eigen::MatrixXd a, Eigen::MatrixXd b) { return a + b; }
我用於此示例的整個代碼是:
#include <eigen-git-mirror/Eigen/Dense>
#include <eigen-git-mirror/unsupported/Eigen/CXX11/Tensor>
#include "pybind11/include/pybind11/eigen.h"
#include "pybind11/include/pybind11/pybind11.h"
Eigen::MatrixXd addition(Eigen::MatrixXd a, Eigen::MatrixXd b) { return a + b; }
Eigen::Tensor<double, 3> addition_tensor(Eigen::Tensor<double, 3> a,
Eigen::Tensor<double, 3> b) {
return a + b;
}
PYBIND11_MODULE(example, m) {
m.def("addition", &addition, "A function which adds two numbers");
m.def("addition_tensor", &addition_tensor,
"A function which adds two numbers");
}
我用g++ -shared -fPIC `python3 -m pybind11 --includes` example.cpp -o example`python3-config --extension-suffix`
編譯了上面的代碼。 有人知道我如何將三維numpy
數組轉換為接受三維Eigen::Tensor
的 function 嗎?
它不被直接支持,這里有一些討論(包括一些代碼來做映射,如果你想把它添加到你的項目中): https://github.com/pybind/pybind11/issues/1377
感謝@John Zwinck 的回答,我可以實現我想要的。 如果有人感興趣,這里是復制:
#include <eigen-git-mirror/Eigen/Dense>
#include <eigen-git-mirror/unsupported/Eigen/CXX11/Tensor>
#include "pybind11/include/pybind11/eigen.h"
#include "pybind11/include/pybind11/numpy.h"
#include "pybind11/include/pybind11/pybind11.h"
Eigen::Tensor<double, 3, Eigen::RowMajor> getTensor(
pybind11::array_t<double> inArray) {
// request a buffer descriptor from Python
pybind11::buffer_info buffer_info = inArray.request();
// extract data an shape of input array
double *data = static_cast<double *>(buffer_info.ptr);
std::vector<ssize_t> shape = buffer_info.shape;
// wrap ndarray in Eigen::Map:
// the second template argument is the rank of the tensor and has to be
// known at compile time
Eigen::TensorMap<Eigen::Tensor<double, 3, Eigen::RowMajor>> in_tensor(
data, shape[0], shape[1], shape[2]);
return in_tensor;
}
pybind11::array_t<double> return_array(
Eigen::Tensor<double, 3, Eigen::RowMajor> inp) {
std::vector<ssize_t> shape(3);
shape[0] = inp.dimension(0);
shape[1] = inp.dimension(1);
shape[2] = inp.dimension(2);
return pybind11::array_t<double>(
shape, // shape
{shape[1] * shape[2] * sizeof(double), shape[2] * sizeof(double),
sizeof(double)}, // strides
inp.data()); // data pointer
}
pybind11::array_t<double> addition(pybind11::array_t<double> a,
pybind11::array_t<double> b) {
Eigen::Tensor<double, 3, Eigen::RowMajor> a_t = getTensor(a);
Eigen::Tensor<double, 3, Eigen::RowMajor> b_t = getTensor(b);
Eigen::Tensor<double, 3, Eigen::RowMajor> res = a_t + b_t;
return return_array(res);
}
PYBIND11_MODULE(example, m) {
m.def("addition", &addition, "A function which adds two numbers");
}
與約翰提到的鏈接中的建議相反,我不介意對Eigen::Tensor
使用RowMajor
存儲順序。 我看到這個存儲順序在tensorflow
代碼中也被多次使用。 我不知道上面的代碼是否不必要地復制數據。
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