Stephen J. Turnbull wrote:
> You take a hunk of the standard library (in this case it would have to
> be an accelerator written in C since you want to compare C++ vs. C) or
> interpreter code, and translate it to the new syntax.
> Now, *INCREF and friends are frequently cited as annoyances or even
Yes, each compiler implement its own compiler ABI, but for me it is not a
problem at all, just provide build with 3 major compilers gcc/clang (due to
binary compatability) and Visual Studio
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[Guido]
> I don't think there's a way to do a PGO build from Visual Studio; but
> a command prompt in the repo can do it using `PCbuild\build.bat --pgo`.
> Just be patient with it.
Thanks! That worked, and was easy, and gave me an executable that runs
"// 10" at supernatural speed.
Alas, Visual
On Sun, Jan 16, 2022 at 1:51 PM Mark Dickinson wrote:
> On Sun, Jan 16, 2022 at 9:28 PM Guido van Rossum wrote:
>
>> Does the optimization for //10 actually help in the real world? [...]
>>
>
> Yep, I don't know. If 10 is *not* the most common small divisor in real
> world code, it must at
On Sun, Jan 16, 2022 at 2:21 PM Tim Peters wrote:
> I have to believe the same is true under Visual Studio 2019, but
> offhand don't know how to prove that. I understand Steve uses PGO to
> build the python.org Windows release, but I've never done that - the
> "Release build" configuration I get
[Tim, incidentally notes that passing 10 as the divisor to inplace_divrem1()
is "impossibly fast" on Windows, consuming less than a third the time as
when passing seemingly any other divisor]
[Mark Dickinson, discovers much the same is true under other, but not all,
Linux-y builds, due to the
On Sun, Jan 16, 2022 at 9:28 PM Guido van Rossum wrote:
> Does the optimization for //10 actually help in the real world? [...]
>
Yep, I don't know. If 10 is *not* the most common small divisor in real
world code, it must at least rank in the top five. I might hazard a guess
that division by 2
As a bystander, this is all fascinating (I had actually anticipated that
the //10 optimization came from PGO).
Does the optimization for //10 actually help in the real world? It would if
people did a lot of manual conversion to decimal, which is easiest
expressed using //10. But presumably for
On Sun, Jan 16, 2022 at 12:08 PM Mark Dickinson wrote:
> So gcc is anticipating divisions by 10 and introducing special-case
> divide-by-reciprocal-multiply code for that case, and presumably the
> profile generated for the PGO backs up this being a common enough case, so
> we end up with the
On Sun, Jan 16, 2022 at 4:11 PM Terry Reedy wrote:
>
>
> https://stackoverflow.com/questions/41183935/why-does-gcc-use-multiplication-by-a-strange-number-in-implementing-integer-divi
>
> and
>
>
> https://stackoverflow.com/questions/30790184/perform-integer-division-using-multiplication
>
> have
On 1/16/2022 7:08 AM, Mark Dickinson wrote:
Now /that/ I certainly wasn't expecting. I don't see the same effect on
macOS / Clang, whether compiling with --enable-optimizations or not;
this appears to be a GCC innovation. And indeed, as Tim suggested, it
turns out that there's no division
On Sat, Jan 15, 2022 at 8:12 PM Tim Peters wrote:
> Something is missing here, but can't guess what without seeing the
> generated machine code.But I trust Mark will do that.
>
Welp, there goes my weekend. :-)
$ python -m timeit -n 150 -s "x = 10**1000" "x//10"
150 loops, best of 5:
12 matches
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