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gh-91247: Use memcpy for list and tuple repeat (#91482) 

* Add _Py_memory_repeat function to pycore_list

* Add _Py_RefcntAdd function to pycore_object

* Use the new functions in tuplerepeat, list_repeat, and list_inplace_repeat
This commit is contained in:
Pieter Eendebak 2022-07-26 04:10:23 +02:00 committed by GitHub
parent 27055d766a
commit 2ef73be891
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GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 73 additions and 65 deletions
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13
Include/internal/pycore_list.h
View File

@ -56,6 +56,19 @@ _PyList_AppendTakeRef(PyListObject *self, PyObject *newitem)
return _PyList_AppendTakeRefListResize(self, newitem);
}
// Repeat the bytes of a buffer in place
static inline void
_Py_memory_repeat(char* dest, Py_ssize_t len_dest, Py_ssize_t len_src)
{
assert(len_src > 0);
Py_ssize_t copied = len_src;
while (copied < len_dest) {
Py_ssize_t bytes_to_copy = Py_MIN(copied, len_dest - copied);
memcpy(dest + copied, dest, bytes_to_copy);
copied += bytes_to_copy;
}
}
typedef struct {
PyObject_HEAD
Py_ssize_t it_index;

10
Include/internal/pycore_object.h
View File

@ -37,6 +37,16 @@ PyAPI_FUNC(void) _Py_NO_RETURN _Py_FatalRefcountErrorFunc(
#define _Py_FatalRefcountError(message) \
_Py_FatalRefcountErrorFunc(__func__, (message))
// Increment reference count by n
static inline void _Py_RefcntAdd(PyObject* op, Py_ssize_t n)
{
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
op->ob_refcnt += n;
}
#define _Py_RefcntAdd(op, n) _Py_RefcntAdd(_PyObject_CAST(op), n)
static inline void
_Py_DECREF_SPECIALIZED(PyObject *op, const destructor destruct)
{

1
Misc/NEWS.d/next/Core and Builtins/2022-03-22-13-12-27.bpo-47091.tJcy-P.rst Normal file
View File

@ -0,0 +1 @@
Improve performance of repetition of :class:`list` and :class:`tuple` by using ``memcpy`` to copy data and performing the reference increments in one step.

73
Objects/listobject.c
View File

@ -551,47 +551,41 @@ list_concat(PyListObject *a, PyObject *bb)
static PyObject *
list_repeat(PyListObject *a, Py_ssize_t n)
{
Py_ssize_t size;
PyListObject *np;
if (n < 0)
n = 0;
if (n > 0 && Py_SIZE(a) > PY_SSIZE_T_MAX / n)
return PyErr_NoMemory();
size = Py_SIZE(a) * n;
if (size == 0)
const Py_ssize_t input_size = Py_SIZE(a);
if (input_size == 0 || n <= 0)
return PyList_New(0);
np = (PyListObject *) list_new_prealloc(size);
assert(n > 0);
if (input_size > PY_SSIZE_T_MAX / n)
return PyErr_NoMemory();
Py_ssize_t output_size = input_size * n;
PyListObject *np = (PyListObject *) list_new_prealloc(output_size);
if (np == NULL)
return NULL;
PyObject **dest = np->ob_item;
PyObject **dest_end = dest + size;
if (Py_SIZE(a) == 1) {
if (input_size == 1) {
PyObject *elem = a->ob_item[0];
Py_SET_REFCNT(elem, Py_REFCNT(elem) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
_Py_RefcntAdd(elem, n);
PyObject **dest_end = dest + output_size;
while (dest < dest_end) {
*dest++ = elem;
}
}
else {
PyObject **src = a->ob_item;
PyObject **src_end = src + Py_SIZE(a);
PyObject **src_end = src + input_size;
while (src < src_end) {
Py_SET_REFCNT(*src, Py_REFCNT(*src) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
_Py_RefcntAdd(*src, n);
*dest++ = *src++;
}
// Now src chases after dest in the same buffer
src = np->ob_item;
while (dest < dest_end) {
*dest++ = *src++;
_Py_memory_repeat((char *)np->ob_item, sizeof(PyObject *)*output_size,
sizeof(PyObject *)*input_size);
}
}
Py_SET_SIZE(np, size);
Py_SET_SIZE(np, output_size);
return (PyObject *) np;
}
@ -743,12 +737,8 @@ PyList_SetSlice(PyObject *a, Py_ssize_t ilow, Py_ssize_t ihigh, PyObject *v)
static PyObject *
list_inplace_repeat(PyListObject *self, Py_ssize_t n)
{
PyObject **items;
Py_ssize_t size, i, j, p;
size = PyList_GET_SIZE(self);
if (size == 0 || n == 1) {
Py_ssize_t input_size = PyList_GET_SIZE(self);
if (input_size == 0 || n == 1) {
Py_INCREF(self);
return (PyObject *)self;
}
@ -759,22 +749,21 @@ list_inplace_repeat(PyListObject *self, Py_ssize_t n)
return (PyObject *)self;
}
if (size > PY_SSIZE_T_MAX / n) {
if (input_size > PY_SSIZE_T_MAX / n) {
return PyErr_NoMemory();
}
Py_ssize_t output_size = input_size * n;
if (list_resize(self, size*n) < 0)
if (list_resize(self, output_size) < 0)
return NULL;
p = size;
items = self->ob_item;
for (i = 1; i < n; i++) { /* Start counting at 1, not 0 */
for (j = 0; j < size; j++) {
PyObject *o = items[j];
Py_INCREF(o);
items[p++] = o;
}
PyObject **items = self->ob_item;
for (Py_ssize_t j = 0; j < input_size; j++) {
_Py_RefcntAdd(items[j], n-1);
}
_Py_memory_repeat((char *)items, sizeof(PyObject *)*output_size,
sizeof(PyObject *)*input_size);
Py_INCREF(self);
return (PyObject *)self;
}

41
Objects/tupleobject.c
View File

@ -495,9 +495,8 @@ tupleconcat(PyTupleObject *a, PyObject *bb)
static PyObject *
tuplerepeat(PyTupleObject *a, Py_ssize_t n)
{
Py_ssize_t size;
PyTupleObject *np;
if (Py_SIZE(a) == 0 || n == 1) {
const Py_ssize_t input_size = Py_SIZE(a);
if (input_size == 0 || n == 1) {
if (PyTuple_CheckExact(a)) {
/* Since tuples are immutable, we can return a shared
copy in this case */
@ -505,42 +504,38 @@ tuplerepeat(PyTupleObject *a, Py_ssize_t n)
return (PyObject *)a;
}
}
if (Py_SIZE(a) == 0 || n <= 0) {
if (input_size == 0 || n <= 0) {
return tuple_get_empty();
}
if (n > PY_SSIZE_T_MAX / Py_SIZE(a))
assert(n>0);
if (input_size > PY_SSIZE_T_MAX / n)
return PyErr_NoMemory();
size = Py_SIZE(a) * n;
np = tuple_alloc(size);
Py_ssize_t output_size = input_size * n;
PyTupleObject *np = tuple_alloc(output_size);
if (np == NULL)
return NULL;
PyObject **dest = np->ob_item;
PyObject **dest_end = dest + size;
if (Py_SIZE(a) == 1) {
if (input_size == 1) {
PyObject *elem = a->ob_item[0];
Py_SET_REFCNT(elem, Py_REFCNT(elem) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
_Py_RefcntAdd(elem, n);
PyObject **dest_end = dest + output_size;
while (dest < dest_end) {
*dest++ = elem;
}
}
else {
PyObject **src = a->ob_item;
PyObject **src_end = src + Py_SIZE(a);
PyObject **src_end = src + input_size;
while (src < src_end) {
Py_SET_REFCNT(*src, Py_REFCNT(*src) + n);
#ifdef Py_REF_DEBUG
_Py_RefTotal += n;
#endif
*dest++ = *src++;
}
// Now src chases after dest in the same buffer
src = np->ob_item;
while (dest < dest_end) {
_Py_RefcntAdd(*src, n);
*dest++ = *src++;
}
_Py_memory_repeat((char *)np->ob_item, sizeof(PyObject *)*output_size,
sizeof(PyObject *)*input_size);
}
_PyObject_GC_TRACK(np);
return (PyObject *) np;