numpy · mattip · Nov 15, 2023 · Jul 27, 2023 · Jul 27, 2023 · J 10BC0 ul 27, 2023
diff --git a/doc/release/upcoming_changes/25138.c_api_removal.rst b/doc/release/upcoming_changes/25138.c_api_removal.rst
@@ -0,0 +1,7 @@
+* The advanced indexing ``MapIter`` and related API has been removed.
+  The (truly) public part of it was not well tested and had only one
+  known user (Theano).  Making it private will simplify improvements
+  to speed up ``ufunc.at`` and make advanced indexing more maintainable
+  and was important for allowing 64 dimensional arrays.
+  Please let us know if this API is important to you so we can find a
+  solution together.
diff --git a/doc/source/reference/c-api/array.rst b/doc/source/reference/c-api/array.rst
@@ -2674,44 +2674,6 @@ cost of a slight overhead.
     neighborhood. Calling this function after every point of the
     neighborhood has been visited is undefined.
 
-Array mapping
--------------
-
-Array mapping is the machinery behind advanced indexing.
-
-.. c:function:: PyObject* PyArray_MapIterArray(PyArrayObject *a, \
-                 PyObject *index)
-
-    Use advanced indexing to iterate an array.
-
-.. c:function:: void PyArray_MapIterSwapAxes(PyArrayMapIterObject *mit, \
-                PyArrayObject **ret, int getmap)
-
-    Swap the axes to o
10BC0
r from their inserted form. ``MapIter`` always puts the
-    advanced (array) indices first in the iteration. But if they are
-    consecutive, it 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 of ``getmap=0``). ``getmap=0`` and
-    ``getmap=1`` undo the other operation.
-
-.. c:function:: void PyArray_MapIterNext(PyArrayMapIterObject *mit)
-
-    This function needs to update the state of the map iterator
-    and point ``mit->dataptr`` to the memory-location of the next object.
-
-    Note that this function never handles an extra operand but provides
-    compatibility for an old (exposed) API.
-
-.. c:function:: PyObject* PyArray_MapIterArrayCopyIfOverlap(PyArrayObject *a, \
-                PyObject *index, int copy_if_overlap, PyArrayObject *extra_op)
-
-    Similar to :c:func:`PyArray_MapIterArray` but with an additional
-    ``copy_if_overlap`` argument. If ``copy_if_overlap != 0``, checks if ``a``
-    has memory overlap with any of the arrays in ``index`` and with
-    ``extra_op``, and make copies as appropriate to avoid problems if the
-    input is modified during the iteration. ``iter->array`` may contain a
-    copied array (WRITEBACKIFCOPY set).
 
 Array scalars
 -------------

diff --git a/numpy/_core/code_generators/cversions.txt b/numpy/_core/code_generators/cversions.txt
@@ -73,4 +73,4 @@
 0x00000011 = ca1aebdad799358149567d9d93cbca09
 
 # Version 18 (NumPy 2.0.0)
-0x00000012 = c48425db43c108beeb57eb7ef155d38e
+0x00000012 = 36c48c1b8952883ca3a636cedaeb441f
diff --git a/numpy/_core/code_generators/generate_numpy_api.py b/numpy/_core/code_generators/generate_numpy_api.py
@@ -17,7 +17,6 @@
         npy_bool obval;
 } PyBoolScalarObject;
 
-extern NPY_NO_EXPORT PyTypeObject PyArrayMapIter_Type;
 extern NPY_NO_EXPORT PyTypeObject PyArrayNeighborhoodIter_Type;
 extern NPY_NO_EXPORT PyBoolScalarObject _PyArrayScalar_BoolValues[2];
 

diff --git a/numpy/_core/code_generators/numpy_api.py b/numpy/_core/code_generators/numpy_api.py
@@ -99,7 +99,8 @@ def get_annotations():
 
 multiarray_funcs_api = {
     '__unused_indices__': [
-        40, 41, 65, 67, 68, 163, 164, 171, 201, 202, 278, 291],
+        40, 41, 65, 67, 68, 163, 164, 171, 201, 202, 278, 291, 293, 294, 295,
+        301],
     'PyArray_GetNDArrayCVersion':           (0,),
     # Unused slot 40, was `PyArray_SetNumericOps`
     # Unused slot 41, was `PyArray_GetNumericOps`,
@@ -352,9 +353,9 @@ def get_annotations():
     'PyDataMem_FREE':                       (289,),
     'PyDataMem_RENEW':                      (290,),
     # Unused slot 291, was `PyDataMem_SetEventHook`
-    'PyArray_MapIterSwapAxes':              (293,),
-    'PyArray_MapIterArray':                 (294,),
-    'PyArray_MapIterNext':                  (295,),
+    # Unused slot 293, was `PyArray_MapIterSwapAxes`
+    # Unused slot 294, was `PyArray_MapIterArray`
+    # Unused slot 295, was `PyArray_MapIterNext`
     # End 1.7 API
     'PyArray_Partition':                    (296,),
     'PyArray_ArgPartition':                 (297,),
@@ -364,7 +365,7 @@ def get_annotations():
     # End 1.9 API
     'PyArray_CheckAnyScalarExact':          (300,),
     # End 1.10 API
-    'PyArray_MapIterArrayCopyIfOverlap':    (301,),
+    # Unused slot 301, was `PyArray_MapIterArrayCopyIfOverlap`
     # End 1.13 API
     'PyArray_ResolveWritebackIfCopy':       (302,),
     'PyArray_SetWritebackIfCopyBase':       (303,),

diff --git a/numpy/_core/include/numpy/ndarraytypes.h b/numpy/_core/include/numpy/ndarraytypes.h
@@ -1319,95 +1319,6 @@ PyArray_MultiIter_ITERS(PyArrayMultiIterObject *multi)
 }
 
 
-/*
- * Store the information needed for fancy-indexing over an array. The
- * fields are slightly unordered to keep consec, dataptr and subspace
- * where they were originally.
- */
-typedef struct {
-        PyObject_HEAD
-        /*
-         * Multi-iterator portion --- needs to be present in this
-         * order to work with PyArray_Broadcast
-         */
-
-        int                   numiter;                 /* number of index-array
-                                                          iterators */
-        npy_intp              size;                    /* size of broadcasted
-                                                          result */
-        npy_intp              index;                   /* current index */
-        int                   nd;                      /* number of dims */
-        npy_intp              dimensions[NPY_MAXDIMS]; /* dimensions */
-        NpyIter               *outer;                  /* index objects
-                                                          iterator */
-        void                  *unused[NPY_MAXDIMS - 2];
-        PyArrayObject         *array;
-        /* Flat iterator for the indexed array. For compatibility solely. */
-        PyArrayIterObject     *ait;
-
-        /*
-         * Subspace array. For binary compatibility (was an iterator,
-         * but only the check for NULL should be used).
-         */
-        PyArrayObject         *subspace;
-
-        /*
-         * if subspace iteration, then this is the array of axes in
-         * the underlying array represented by the index objects
-         */
-        int                   iteraxes[NPY_MAXDIMS];
-        npy_intp              fancy_strides[NPY_MAXDIMS];
-
-        /* pointer when all fancy indices are 0 */
-        char                  *baseoffset;
-
-        /*
-         * after binding consec denotes at which axis the fancy axes
-         * are inserted.
-         */
-        int                   consec;
-        char                  *dataptr;
-
-        int                   nd_fancy;
-        npy_intp              fancy_dims[NPY_MAXDIMS];
-
-        /*
-         * Whether the iterator (any of the iterators) requires API.  This is
-         * unused by NumPy itself; ArrayMethod flags are more precise.
-         */
-        int                   needs_api;
-
-        /*
-         * Extra op information.
-         */
-        PyArrayObject         *extra_op;
-        PyArray_Descr         *extra_op_dtype;         /* desired dtype */
-        npy_uint32            *extra_op_flags;         /* Iterator flags */
-
-        NpyIter               *extra_op_iter;
-        NpyIter_IterNextFunc  *extra_op_next;
-        char                  **extra_op_ptrs;
-
-        /*
-         * Information about the iteration state.
-         */
-        NpyIter_IterNextFunc  *outer_next;
-        char                  **outer_ptrs;
-        npy_intp              *outer_strides;
-
-        /*
-         * Information about the subspace iterator.
-         */
-        NpyIter               *subspace_iter;
-        NpyIter_IterNextFunc  *subspace_next;
-        char                  **subspace_ptrs;
-        npy_intp              *subspace_strides;
-
-        /* Count for the external loop (which ever it is) for API iteration */
-        npy_intp              iter_count;
-
-} PyArrayMapIterObject;
-
 enum {
     NPY_NEIGHBORHOOD_ITER_ZERO_PADDING,
     NPY_NEIGHBORHOOD_ITER_ONE_PADDING,

diff --git a/numpy/_core/src/common/lowlevel_strided_loops.h b/numpy/_core/src/common/lowlevel_strided_loops.h
@@ -5,6 +5,7 @@
 #include "array_method.h"
 #include "dtype_transfer.h"
 #include "mem_overlap.h"
+#include "mapping.h"
 
 /* For PyArray_ macros used below */
 #include "numpy/ndarrayobject.h"

diff --git a/numpy/_core/src/multiarray/_multiarray_tests.c.src b/numpy/_core/src/multiarray/_multiarray_tests.c.src
@@ -467,132 +467,6 @@ clean_ax:
 }
 
 
-typedef void (*inplace_map_binop)(PyArrayMapIterObject *, PyArrayIterObject *);
-
-static void npy_float64_inplace_add(PyArrayMapIterObject *mit, PyArrayIterObject *it)
-{
-    int index = mit->size;
-    while (index--) {
-        ((npy_float64*)mit->dataptr)[0] = ((npy_float64*)mit->dataptr)[0] + ((npy_float64*)it->dataptr)[0];
-
-        PyArray_MapIterNext(mit);
-        PyArray_ITER_NEXT(it);
-    }
-}
-
-inplace_map_binop addition_funcs[] = {
-npy_float64_inplace_add,
-NULL};
-
-int type_numbers[] = {
-NPY_FLOAT64,
--1000};
-
-
-
-static int
-map_increment(PyArrayMapIterObject *mit, PyObject *op, inplace_map_binop add_inplace)
-{
-    PyArrayObject *arr = NULL;
-    PyArrayIterObject *it;
-    PyArray_Descr *descr;
-
-    if (mit->ait == NULL) {
-        return -1;
-    }
-    descr = PyArray_DESCR(mit->ait->ao);
-    Py_INCREF(descr);
-    arr = (PyArrayObject *)PyArray_FromAny(op, descr,
-                                0, 0, NPY_ARRAY_FORCECAST, NULL);
-    if (arr == NULL) {
-        return -1;
-    }
-
-    if ((mit->subspace != NULL) && (mit->consec)) {
-        PyArray_MapIterSwapAxes(mit, (PyArrayObject **)&arr, 0);
-        if (arr == NULL) {
-            return -1;
-        }
-    }
-
-    if ((it = (PyArrayIterObject *)\
-            PyArray_BroadcastToShape((PyObject *)arr, mit->dimensions,
-                                     mit->nd)) == NULL) {
-        Py_DECREF(arr);
-
-        return -1;
-    }
-
-    (*add_inplace)(mit, it);
-
-    Py_DECREF(arr);
-    Py_DECREF(it);
-    return 0;
-}
-
-
-static PyObject *
-inplace_increment(PyObject *dummy, PyObject *args)
-{
-    PyObject *arg_a = NULL, *index=NULL, *inc=NULL;
-    PyArrayObject *a;
-    inplace_map_binop add_inplace = NULL;
-    int type_number = -1;
-    int i =0;
-    PyArrayMapIterObject * mit;
-
-    if (!PyArg_ParseTuple(args, "OOO", &arg_a, &index,
-            &inc)) {
-        return NULL;
-    }
-    if (!PyArray_Check(arg_a)) {
-         PyErr_SetString(PyExc_ValueError, "needs an ndarray as first argument");
-         return NULL;
-    }
-    a = (PyArrayObject *) arg_a;
-
-    if (PyArray_FailUnlessWriteable(a, "input/output array") < 0) {
-        return NULL;
-    }
-
-    if (PyArray_NDIM(a) == 0) {
-        PyErr_SetString(PyExc_IndexError, "0-d arrays can't be indexed.");
-        return NULL;
-    }
-    type_number = PyArray_TYPE(a);
-
-    while (type_numbers[i] >= 0 && addition_funcs[i] != NULL){
-        if (type_number == type_numbers[i]) {
-            add_inplace = addition_funcs[i];
-            break;
-        }
-        i++ ;
-    }
-
-    if (add_inplace == NULL) {
-        PyErr_SetString(PyExc_TypeError, "unsupported type for a");
-        return NULL;
-    }
-
-    mit = (PyArrayMapIterObject *) PyArray_MapIterArray(a, index);
-    if (mit == NULL) {
-        goto fail;
-    }
-
-    if (map_increment(mit, inc, add_inplace) != 0) {
-        goto fail;
-    }
-
-    Py_DECREF(mit);
-
-    Py_RETURN_NONE;
-
-fail:
-    Py_XDECREF(mit);
-
-    return NULL;
-}
-
 /*
  * Helper to test fromstring of 0 terminated strings, as the C-API supports
  * the -1 length identifier.
@@ -2302,9 +2176,6 @@ static PyMethodDef Multiarray_TestsMethods[] = {
     {"test_neighborhood_iterator_oob",
         test_neighborhood_iterator_oob,
         METH_VARARGS, NULL},
-    {"test_inplace_increment",
-        inplace_increment,
-        METH_VARARGS, NULL},
     {"fromstring_null_term_c_api",
         fromstring_null_term_c_api,
         METH_O, NULL},