我正在做一些计算在c++的帮助下Eigen库,函数是这样的:
MatrixXd Cov(MatrixXd Data)
{
VectorXd meanVector;
...
return Covariance;
}
. .在wrap python函数中:
static PyObject *Wrap_Cov(PyObject *self,PyObject *args)
{
Pyobject *Objectdata;
if(!PyArg_ParseTuple(args,"O", &ObjectData))
return NULL;
Cov(ObjectData);
return Py_BuildValue("O",&covariance_answer);
}
显然,Python不知道我定义的"对象",它无法将"MatrixXd"转换为"对象",我认为这是某种"数组",而不是"对象"
如何在不使用boost的情况下做到这一点?
如果要接口用不同语言编写的数值模块,那么最好保持交换的数据尽可能平直。
libeigen实数矩阵的最平坦表示是实数类型(float或double)的c数组
这是一个c++¹示例
#include <stdexcept>
#include <iostream>
#include <string>
#include <sstream>
#include <python2.7/Python.h>
#include <eigen3/Eigen/Dense>
using std::size_t;
typedef double real_t;
typedef Eigen::Matrix<real_t, Eigen::Dynamic, Eigen::Dynamic>
Matrix;
static PyObject* p_eigen_python_error(NULL);
static PyObject *
randomDxDMatrix(PyObject *self, PyObject *args) {
PyObject* p(NULL);
PyObject* item(NULL);
try{
size_t d(0);
PyArg_ParseTuple(args, "L", &d);
Matrix M = Matrix::Random(d,d);
size_t length = d * d;
p = PyList_New(length);
if (p == NULL) {
std::stringstream msg;
msg << "Could not allocate a Pylist of "
<< d << "x" << d << " = " << d*d
<< " size for the return Object";
throw std::runtime_error(msg.str().c_str());
} else {
for (size_t i = 0; i < length; ++i) {
item = PyFloat_FromDouble(M.data()[i]);
PyList_SET_ITEM(p, i, item);
}
}
} catch (const std::exception& e) {
delete p; p = NULL;
delete item; item = NULL;
std::string msg = ("randomDxDMatrix failed: ");
msg += e.what();
PyErr_SetString(p_eigen_python_error, msg.c_str());
}
return p;
}
static PyMethodDef EigenMethods[] = {
{"randomDxDMatrix", randomDxDMatrix, METH_VARARGS,
"Gets a random DxD matrix column-major as a list of (python) floats"},
{NULL, NULL, 0, NULL} /* Sentinel */
};
PyMODINIT_FUNC
initeigen_python(void) {
PyObject* p;
p = Py_InitModule("eigen_python", EigenMethods);
if (p == NULL)
return;
p_eigen_python_error = PyErr_NewException(
const_cast<char*>("eigen_python.error"),
NULL, NULL
);
Py_INCREF(p_eigen_python_error);
PyModule_AddObject(p, "error", p_eigen_python_error);
}
这里是setup_eigen_python.py
from distutils.core import setup, Extension
cpp_args = ['-Wall', '-pedantic']
cxx_args = ['-std=c++11'].extend(cpp_args)
module_eigen_python = Extension('eigen_python',
define_macros = [('MAJOR_VERSION', '0'),
('MINOR_VERSION', '1')],
include_dirs = ['/usr/local/include'],
sources = ['eigen_python.cpp'],
extra_compile_args = cpp_args
# sources = ['eigen_python.cxx'],
# extra_compile_args = cxx_args
)
setup (name = 'eigen_python',
version = '0.1',
description = 'This is just a demo',
author = 'Solkar',
url = 'http://stackoverflow.com/questions'
+ '/15573557/call-c-using-eigen-library-function-in-python',
long_description = 'just a toy',
ext_modules = [module_eigen_python])
与
一样使用python2.7 setup_eigen_python.py install --user
这是一个小的测试驱动程序
import eigen_python as ep
import numpy as np
DIM = 4
M = np.array(ep.randomDxDMatrix(DIM), order="F")
M.shape= DIM,DIM
print(M)
¹特别是,但到目前为止不限于,因为没有boost,我更喜欢使用c++ 2011标准的功能,如auto
和std::unique_ptr
,但我不知道QO是否对此有足够的支持。