Function PyArray_MapIterSwapAxes

numpy/core/src/multiarray/mapping.c:125–161

NUMPY_API * * Swap the axes to or from their inserted form. MapIter always puts the * advanced (array) indices first in the iteration. But if they are * consecutive, will insert/transpose them back before returning. * This is stored as `mit->consec != 0` (the place where they are inserted) * For assignments, the opposite happens: The values to be assigned are * transposed (getmap=1 instead

 * undo the other operation.
 */
NPY_NO_EXPORT void
PyArray_MapIterSwapAxes(PyArrayMapIterObject *mit, PyArrayObject **ret, int getmap)
{
    PyObject *new;
    PyArray_Dims permute;
    npy_intp d[NPY_MAXDIMS];
    PyArrayObject *arr;

    permute.ptr = d;
    permute.len = mit->nd;

    /*
     * arr might not have the right number of dimensions
     * and need to be reshaped first by pre-pending ones
     */
    arr = *ret;
    if (PyArray_NDIM(arr) != mit->nd) {
        for (int i = 1; i <= PyArray_NDIM(arr); i++) {
            permute.ptr[mit->nd-i] = PyArray_DIMS(arr)[PyArray_NDIM(arr)-i];
        }
        for (int i = 0; i < mit->nd-PyArray_NDIM(arr); i++) {
            permute.ptr[i] = 1;
        }
        new = PyArray_Newshape(arr, &permute, NPY_ANYORDER);
        Py_DECREF(arr);
        *ret = (PyArrayObject *)new;
        if (new == NULL) {
            return;
        }
    }

    _get_transpose(mit->nd_fancy, mit->consec, mit->nd, getmap, permute.ptr);

    new = PyArray_Transpose(*ret, &permute);
    Py_DECREF(*ret);
    *ret = (PyArrayObject *)new;
}

static inline void
multi_DECREF(PyObject **objects, npy_intp n)