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gh-157742: Check for signals every 64th iteration in the int arithmetic loops #157744

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gh-157742: Check for signals every 64th iteration in the int arithmetic loops #157744

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Check for signals every 64th iteration in the int arithmetic loops
eendebakpt Sep 18, 2026
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📜🤖 Added by blurb_it.
blurb-it[bot] Sep 18, 2026
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-09-18-11-15-58.gh-issue-157742.FjDXQl.rst
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@@ -0,0 +1 @@
Improve performance of arithmetic operations like multiplication and division for :class:`int`.

@skirpichev skirpichev Sep 20, 2026

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This affects also string conversion.

@eendebakpt eendebakpt Sep 20, 2026

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Yes, but the gain is not really worth mentioning. For small number of digits the overhead dominates, for large number of digits the bigint algorithm in _pylong takes over.

@skirpichev skirpichev Sep 21, 2026

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On your benchmarks: 1.10x speedup, no? Looks too big for noise.

15 changes: 8 additions & 7 deletions Objects/longobject.c
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Expand Up @@ -113,9 +113,10 @@ maybe_small_long(PyLongObject *v)
*/
#define HUGE_EXP_CUTOFF 60

#define SIGCHECK(PyTryBlock) \
do { \
if (PyErr_CheckSignals()) PyTryBlock \
/* Check for signals on every 64th iteration `i` of a loop. */
#define SIGCHECK(i, PyTryBlock) \
do { \
if ((((i) & 63) == 63) && PyErr_CheckSignals()) PyTryBlock \
} while(0)

/* Normalize (remove leading zeros from) an int object.
Expand Down Expand Up @@ -2186,7 +2187,7 @@ long_to_decimal_string_internal(PyObject *aa,
hi /= _PyLong_DECIMAL_BASE;
}
/* check for keyboard interrupt */
SIGCHECK({
SIGCHECK(i, {
Py_DECREF(scratch);
return -1;
});
Expand Down Expand Up @@ -3381,7 +3382,7 @@ x_divrem(PyLongObject *v1, PyLongObject *w1, PyLongObject **prem)
/* inner loop: divide vk[0:size_w+1] by w0[0:size_w], giving
single-digit quotient q, remainder in vk[0:size_w]. */

SIGCHECK({
SIGCHECK(vk - v0, {
Py_DECREF(a);
Py_DECREF(w);
Py_DECREF(v);
Expand Down Expand Up @@ -3954,7 +3955,7 @@ x_mul(PyLongObject *a, PyLongObject *b)
digit *pz = z->long_value.ob_digit + (i << 1);
digit *pa = a->long_value.ob_digit + i + 1;

SIGCHECK({
SIGCHECK(i, {
Py_DECREF(z);
return NULL;
});
Expand Down Expand Up @@ -4006,7 +4007,7 @@ x_mul(PyLongObject *a, PyLongObject *b)
digit *pb = b->long_value.ob_digit;
digit *pbend = b->long_value.ob_digit + size_b;

SIGCHECK({
SIGCHECK(i, {
Py_DECREF(z);
return NULL;
});
Expand Down
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