support for noconvert

[nbecker]

It seems noconvert is not supported? I tried adding noconvert to my (now classic) summer.cc:

#include <numpy/arrayobject.h>
#include "pybind11/numpy.h" // complex
#include "pybind11/pybind11.h"
#include "pybind11/operators.h"
#include "numpy/arrayobject.h"
//#include "ndarray/pybind11.h"
#include "xtensor/xtensor.hpp"
#include "xtensor/xcontainer.hpp"
#include "xtensor-python/pyarray.hpp"

#include <complex>

namespace py = pybind11;

PYBIND11_PLUGIN (summer){
 if (_import_array() < 0){
 PyErr_SetString(PyExc_ImportError, "numpy.core.multiarray failed to import");
 return nullptr;
 }

 py::module m("summer", "pybind11 example plugin");

 // m.def("sum", [](xt::pyarray<double> const& x){
 // xt::xtensor<double, 1> tmp(x);
 // double sum = 0;
 // for (auto e : tmp)
 // sum += e;
 // return sum;
 // });

 m.def("sum", [](xt::pyarray<std::complex<double>> const& x){
 std::complex<double> sum = 0;
 for (auto e : x)
 sum += e;
 return sum;
 },
 py::arg("inp").noconvert()
 );

 m.def("sum", [](xt::pyarray<double> const& x){
 double sum = 0;
 for (auto e : x)
 sum += e;
 return sum;
 },
 py::arg("inp").noconvert()
 );


 return m.ptr();
}

It seems to have no effect. If I reverse the order of the defs (double is 1st), then when passing a complex array I get the numpy warning of discarding imag part. If I use the order above, the time for processing float array is much more than for complex array, suggesting there is conversion.

[SylvainCorlay]

Thanks for the pointers. We should probably support this.

[nbecker]

I don't really know what I'm doing here, but this seems to work

diff -r 53dcd0192dc2 include/xtensor-python/pytensor.hpp
--- a/include/xtensor-python/pytensor.hpp	Sat Apr 08 15:46:37 2017 +0200
+++ b/include/xtensor-python/pytensor.hpp	Wed Apr 12 08:04:52 2017 -0400
@@ -43,9 +43,16 @@
{
 using type = xt::pytensor<T, N>
 
- bool load(handle src, bool)
+ bool load(handle src, bool convert)
{
- value = type::ensure(src);
+ if (!convert){
+ if (!PyArray_Check(src.ptr()))
+ return false;
+ int type_num = xt::detail::numpy_traits<T>::type_num;
+ if (PyArray_TYPE(src.ptr()) != type_num)
+ return false;
+ }
+ value = type::ensure(src);
 return static_cast<bool>(value);
 }
 
@@ -56,6 +63,26 @@
 
 PYBIND11_TYPE_CASTER(type, handle_type_name<type>::name());
 };
+ template <class T>
+ struct numpy_traits
+{
+ private:
+
+ constexpr static const int value_list[15] ={
+ NPY_BOOL,
+ NPY_BYTE, NPY_UBYTE, NPY_SHORT, NPY_USHORT,
+ NPY_INT, NPY_UINT, NPY_LONGLONG, NPY_ULONGLONG,
+ NPY_FLOAT, NPY_DOUBLE, NPY_LONGDOUBLE,
+ NPY_CFLOAT, NPY_CDOUBLE, NPY_CLONGDOUBLE
+ };
+
+ public:
+
+ using value_type = std::remove_const_t<T>
+
+ static constexpr int type_num = value_list[pybind11::detail::is_fmt_numeric<value_type>::index];
+ };
+
 }
 }
 

[SylvainCorlay]

Thanks for the patch! I will try it out.

[nbecker]

I am working on a better patch, but I'm struggling with git. Basically, the same diff for pytensor and pyarray, and refactor the traits into it's own header

[nbecker]

#75 I'm a git(hub) newb, so hopefully I did this OK

…

On Wed, Apr 12, 2017 at 9:37 AM Sylvain Corlay ***@***.***> wrote: Thanks for the patch! I will try it out. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#73 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAHK0ATpi0b46x9VghyNgOy29KgNGdy8ks5rvNOhgaJpZM4M6Qeg> .

[nbecker]

Also, patch only addresses typenum mismatch, maybe there are other array flags that imply conversion that should be checked?

It would be nice if the numpy ABI had a function to check whether array can be imported without conversion, but I didn't see one.

[wolfv]

Fixed :)