[Python-Dev] Speeding up CPython 5-10%

[zreed at fastmail.com]

Your criticisms may very well be true. IIRC though, I wrote that pass
because what was available was not general enough. The stackdepth_walk
function made assumptions that, while true of code generated by the
current cpython frontend, were not universally true. If a goal is to
move this calculation after any bytecode optimization, something along
these lines seems like it will eventually be necessary.
 
Anyway, just offering things already written. If you don't feel it's
useful, no worries.
 
 
On Wed, May 18, 2016, at 11:35 AM, Cesare Di Mauro wrote:
> 2016-05-17 8:25 GMT+02:00 <zreed at fastmail.com>:
>> In the project https://github.com/zachariahreed/byteasm I
>> mentioned on
>>  the list earlier this month, I have a pass that to computes
>>  stack usage
>>  for a given sequence of bytecodes. It seems to be a fair bit more
>>  agressive than cpython. Maybe it's more generally useful. It's pure
>>  python rather than C though.
>>
> IMO it's too big, resource hungry, and slower, even if you convert
> it in C.
>
> If you take a look at the current stackdepth_walk function which
> CPython uses, it's much smaller (not even 50 lines in simple C code)
> and quite efficient.
>
> Currently the problem is that it doesn't return the maximum depth of
> the tree, but it updates the intermediate/current maximum, and *then*
> it uses it for the subsequent calculations. So, the depth artificially
> grows, like in the reported cases.
>
> It doesn't require a complete rewrite, but spending some time for fine-
> tuning it.
>
> Regards
> Cesare
 
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