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#ifndef PYTHONIC_NUMPY_DIFF_HPP
#define PYTHONIC_NUMPY_DIFF_HPP
#include "pythonic/include/numpy/diff.hpp"
#include "pythonic/utils/functor.hpp"
#include "pythonic/types/ndarray.hpp"
#include "pythonic/numpy/asarray.hpp"
PYTHONIC_NS_BEGIN
namespace numpy
{
namespace details
{
template <class E>
types::ndarray<typename E::dtype, types::array<long, E::value>>
diff(E const &arr, long n, long axis)
{
auto shape = sutils::getshape(arr);
auto stride = (axis == E::value - 1)
? arr.template shape<E::value - 1>()
: std::accumulate(shape.begin() + axis + 1, shape.end(),
1L, std::multiplies<long>());
--shape[axis];
// this does not leak, but uses slightly too much memory
auto out = arr.reshape(shape);
auto iter = arr.fbegin();
auto out_iter = out.fbegin();
if (axis == E::value - 1) {
for (long i = 0, sz = arr.flat_size(); i < sz; i += stride) {
auto prev = *(iter + i);
for (long k = 1; k < stride; ++k, ++out_iter) {
auto nprev = *(iter + i + k);
*(out_iter) = nprev - prev;
prev = nprev;
}
}
} else {
iter += stride;
for (auto out_end = out.fend(); out_iter != out_end; ++out_iter) {
*out_iter = *iter++ - *out_iter;
}
}
if (n == 1)
return out;
else
return diff(out, n - 1, axis);
}
}
template <class E>
types::ndarray<typename E::dtype, types::array<long, E::value>>
diff(E const &expr, long n, long axis)
{
if (axis < 0)
axis += E::value;
// that's the only allocation that should happen
return details::diff(array(expr), n, axis);
}
}
PYTHONIC_NS_END
#endif
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