gh-161242: Add a freelist for traceback objects - #161243

"""pyperf micro-benchmarks for raising and catching exceptions.

Usage: python bench_exc.py [pyperf args...]
"""
import sys
import pyperf


def keyerror(d, key, fallback):
    try:
        return d[key]
    except KeyError:
        return fallback(key, d)


def attrerror(obj, name, default):
    try:
        return obj.x
    except AttributeError:
        return default + name


def valueerror_raise(x):
    try:
        raise ValueError
    except ValueError:
        return x


def valueerror_raise_inst(x):
    try:
        raise ValueError(x)
    except ValueError:
        return x


def stopiter(it):
    try:
        return next(it)
    except StopIteration:
        return it


def through_frame(x):
    try:
        raiser(x)
    except ValueError:
        return x


def raiser(x):
    raise ValueError(x)


class NoX:
    pass


def make_bench(fn, *args):
    def bench(loops):
        r = range(loops)
        t0 = pyperf.perf_counter()
        for _ in r:
            fn(*args); fn(*args); fn(*args); fn(*args)
        return pyperf.perf_counter() - t0
    return bench


if __name__ == "__main__":
    a = float(len(sys.argv)) * 2.5
    runner = pyperf.Runner()
    runner.bench_time_func("raise ValueError", make_bench(valueerror_raise, a))
    runner.bench_time_func("raise ValueError(x)", make_bench(valueerror_raise_inst, a))
    runner.bench_time_func("raise through frame", make_bench(through_frame, a))
    runner.bench_time_func("d[key] KeyError", make_bench(keyerror, {}, a, lambda k, d: k))
    runner.bench_time_func("next() StopIteration", make_bench(stopiter, iter(())))
    runner.bench_time_func("obj.x AttributeError", make_bench(attrerror, NoX(), "n" * 2, "d" * 2))

"""Exception-heavy workloads in the style of real code, for pyperf.

Each benchmark raises and catches exceptions through Python frames as a
side effect of ordinary work, which is the case the traceback and
exception freelists target.  Usage: python bench_exc_macro.py [pyperf args]
"""
import random
import pyperf

random.seed(12345)


# 1. Data cleaning: parse a column of mixed strings with try/except fallbacks
#    (int -> float -> keep string), the usual idiom for CSV cleanup.
_RAW_COLUMN = []
for _i in range(2000):
    _r = random.random()
    if _r < 0.5:
        _RAW_COLUMN.append(str(random.randint(-10**6, 10**6)))
    elif _r < 0.8:
        _RAW_COLUMN.append(repr(random.uniform(-1e6, 1e6)))
    else:
        _RAW_COLUMN.append(random.choice(["n/a", "", "NULL", "12,5", "1e", "x"]))


def to_number(s):
    try:
        return int(s)
    except ValueError:
        pass
    try:
        return float(s)
    except ValueError:
        return s


def bench_parse_column(loops):
    column = _RAW_COLUMN
    t0 = pyperf.perf_counter()
    for _ in range(loops):
        total = 0
        for s in column:
            v = to_number(s)
            if type(v) is not str:
                total += 1
    return pyperf.perf_counter() - t0


# 2. Counting with the classic try/except KeyError idiom on a text with a
#    long tail of rare words (every first occurrence raises).
_WORDS = ([f"w{i}" for i in range(50) for _ in range(20)]
          + [f"rare{i}" for i in range(3000)])
random.shuffle(_WORDS)


def bench_count_keyerror(loops):
    words = _WORDS
    t0 = pyperf.perf_counter()
    for _ in range(loops):
        counts = {}
        for w in words:
            try:
                counts[w] += 1
            except KeyError:
                counts[w] = 1
    return pyperf.perf_counter() - t0


# 3. Template-engine style variable resolution: try a dict lookup, then an
#    attribute, then an index, like Django's Variable._resolve_lookup().
class _Ctx:
    def __init__(self, **kw):
        self.__dict__.update(kw)


def resolve(obj, bit):
    try:
        return obj[bit]
    except (TypeError, KeyError, IndexError):
        pass
    try:
        return getattr(obj, bit)
    except AttributeError:
        pass
    try:
        return obj[int(bit)]
    except (ValueError, TypeError, IndexError, KeyError):
        raise LookupError(bit)


_CONTEXT = {"user": _Ctx(name="Ada", tags=["a", "b", "c"], profile={"city": "London"}),
            "items": [_Ctx(title=f"t{i}", price=i) for i in range(20)]}
_LOOKUPS = ["user.name", "user.tags.1", "user.profile.city", "items.3.title",
            "items.7.price", "user.missing", "items.25.title"]


def render_var(context, path):
    obj = context
    for bit in path.split("."):
        try:
            obj = resolve(obj, bit)
        except LookupError:
            return ""
    return obj


def bench_template_resolve(loops):
    ctx = _CONTEXT
    lookups = _LOOKUPS
    t0 = pyperf.perf_counter()
    for _ in range(loops):
        for _r in range(50):
            for p in lookups:
                render_var(ctx, p)
    return pyperf.perf_counter() - t0


# 4. Duck typing: optional protocol methods probed with try/except
#    AttributeError in Python code, over a mix of object kinds.
class _WithClose:
    def close(self):
        return 1


class _WithFlush:
    def flush(self):
        return 2


class _Plain:
    pass


_OBJECTS = [random.choice([_WithClose, _WithFlush, _Plain])() for _ in range(1000)]


def finish(obj):
    n = 0
    try:
        obj.flush()
        n += 1
    except AttributeError:
        pass
    try:
        obj.close()
        n += 1
    except AttributeError:
        pass
    return n


def bench_duck_typing(loops):
    objs = _OBJECTS
    t0 = pyperf.perf_counter()
    for _ in range(loops):
        for o in objs:
            finish(o)
    return pyperf.perf_counter() - t0


# 5. Python-level iterator classes: StopIteration raised from __next__
#    through a Python frame once per (short) iteration.
class Countdown:
    def __init__(self, n):
        self.n = n

    def __iter__(self):
        return self

    def __next__(self):
        if self.n <= 0:
            raise StopIteration
        self.n -= 1
        return self.n


def bench_iterator_class(loops):
    t0 = pyperf.perf_counter()
    for _ in range(loops):
        for _r in range(500):
            for _x in Countdown(3):
                pass
    return pyperf.perf_counter() - t0


if __name__ == "__main__":
    runner = pyperf.Runner()
    runner.bench_time_func("parse mixed column (int/float/str)", bench_parse_column)
    runner.bench_time_func("word count via KeyError", bench_count_keyerror)
    runner.bench_time_func("template variable resolve", bench_template_resolve)
    runner.bench_time_func("duck typing AttributeError", bench_duck_typing)
    runner.bench_time_func("iterator class StopIteration", bench_iterator_class)