diff --git a/Lib/test/test_range.py b/Lib/test/test_range.py index 7be76b32ac2..3870b153688 100644 --- a/Lib/test/test_range.py +++ b/Lib/test/test_range.py @@ -542,6 +542,7 @@ class RangeTest(unittest.TestCase): for start in limits for end in limits for step in (-2**63, -2**31, -2, -1, 1, 2)] + test_ranges += [(-2**63, 2**63-2, 1)] # regression test for gh-100810 for start, end, step in test_ranges: iter1 = range(start, end, step) diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-01-03-20-59-20.gh-issue-100726.W9huFl.rst b/Misc/NEWS.d/next/Core and Builtins/2023-01-03-20-59-20.gh-issue-100726.W9huFl.rst new file mode 100644 index 00000000000..2c93098b347 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2023-01-03-20-59-20.gh-issue-100726.W9huFl.rst @@ -0,0 +1 @@ +Optimize construction of ``range`` object for medium size integers. diff --git a/Objects/rangeobject.c b/Objects/rangeobject.c index 992e7c079de..b4d0bbf32c8 100644 --- a/Objects/rangeobject.c +++ b/Objects/rangeobject.c @@ -171,6 +171,49 @@ range_dealloc(rangeobject *r) PyObject_Free(r); } +static unsigned long +get_len_of_range(long lo, long hi, long step); + +/* Return the length as a long, -2 for an overflow and -1 for any other type of error + * + * In case of an overflow no error is set + */ +static long compute_range_length_long(PyObject *start, + PyObject *stop, PyObject *step) { + int overflow = 0; + + long long_start = PyLong_AsLongAndOverflow(start, &overflow); + if (overflow) { + return -2; + } + if (long_start == -1 && PyErr_Occurred()) { + return -1; + } + long long_stop = PyLong_AsLongAndOverflow(stop, &overflow); + if (overflow) { + return -2; + } + if (long_stop == -1 && PyErr_Occurred()) { + return -1; + } + long long_step = PyLong_AsLongAndOverflow(step, &overflow); + if (overflow) { + return -2; + } + if (long_step == -1 && PyErr_Occurred()) { + return -1; + } + + unsigned long ulen = get_len_of_range(long_start, long_stop, long_step); + if (ulen > (unsigned long)LONG_MAX) { + /* length too large for a long */ + return -2; + } + else { + return (long)ulen; + } +} + /* Return number of items in range (lo, hi, step) as a PyLong object, * when arguments are PyLong objects. Arguments MUST return 1 with * PyLong_Check(). Return NULL when there is an error. @@ -191,6 +234,21 @@ compute_range_length(PyObject *start, PyObject *stop, PyObject *step) PyObject *zero = _PyLong_GetZero(); // borrowed reference PyObject *one = _PyLong_GetOne(); // borrowed reference + assert(PyLong_Check(start)); + assert(PyLong_Check(stop)); + assert(PyLong_Check(step)); + + /* fast path when all arguments fit into a long integer */ + long len = compute_range_length_long(start, stop, step); + if (len >= 0) { + return PyLong_FromLong(len); + } + else if (len == -1) { + /* unexpected error from compute_range_length_long, we propagate to the caller */ + return NULL; + } + assert(len == -2); + cmp_result = PyObject_RichCompareBool(step, zero, Py_GT); if (cmp_result == -1) return NULL;