delta/cpython-git.git/Objects, branch faster-bytes-iter

A (very) slight speed improvement for iterating over bytes

2020-08-02T22:51:54+00:00

My mentee @xvxvxvxvxv noticed that iterating over array.array is
slightly faster than iterating over bytes.  Looking at the source I
observed that arrayiter_next() calls `getitem(ao, it->index++)` wheras
striter_next() uses the idiom (paraphrased)

    item = PyLong_FromLong(seq->ob_sval[it->it_index]);
    if (item != NULL)
        ++it->it_next;
    return item;

I'm not 100% sure but I think that the second version has fewer
opportunity for the CPU to overlap the `index++` operation with the
rest of the code (which in both cases involves a call).  So here I am
optimistically incrementing the index -- if the PyLong_FromLong() call
fails, this will leave the iterator pointing at the next byte, but
honestly I doubt that anyone would seriously consider resuming use of
the iterator after that kind of failure (it would have to be a
MemoryError).  And the author of arrayiter_next() made the same
consideration (or never ever gave it a thought :-).

With this, a loop like

    for _ in b: pass

is now slightly *faster* than the same thing over an equivalent array,
rather than slightly *slower* (in both cases a few percent).

bpo-41342: Convert int.round to Argument Clinic (GH-21549)

2020-07-20T12:57:37+00:00

bpo-41334: Convert constructors of str, bytes and bytearray to Argument Clinic (GH-21535)

2020-07-20T12:53:55+00:00

bpo-41343: Convert methods of complex to Argument Clinic (GH-21550)

2020-07-20T12:53:29+00:00

bpo-41333: Convert OrderedDict.pop() to Argument Clinic (GH-21534)

2020-07-19T06:18:55+00:00

bpo-41295: Reimplement the Carlo Verre "hackcheck" (GH-21528)

2020-07-18T21:19:50+00:00

Walk down the MRO backwards to find the type that originally defined the final `tp_setattro`, then make sure we are not jumping over intermediate C-level bases with the Python-level call.

Automerge-Triggered-By: @gvanrossum

bpo-41262: Convert memoryview to Argument Clinic. (GH-21421)

2020-07-18T08:12:05+00:00

Fix a small grammatical mistake in a comment (GH-21526)

2020-07-17T20:09:21+00:00

Automerge-Triggered-By: @brettcannon

bpo-40941: Unify implicit and explicit state in the frame and generator objects into a single value. (GH-20803)

2020-07-17T10:44:23+00:00

* Merge gen and frame state variables into one.

* Replace stack pointer with depth in PyFrameObject. Makes code easier to read and saves a word of memory.

bpo-36346: Make using the legacy Unicode C API optional (GH-21437)

2020-07-10T20:26:06+00:00

Add compile time option USE_UNICODE_WCHAR_CACHE. Setting it to 0
makes the interpreter not using the wchar_t cache and the legacy Unicode C API.