On Sat, May 8, 2021 at 1:32 PM Pablo Galindo Salgado <pablog...@gmail.com> wrote:
> > We can't piggy back on -OO as the only way to disable this, it needs to > have an option of its own. -OO is unusable as code that relies on > "doc"strings as application data such as > http://www.dabeaz.com/ply/ply.html exists. > > -OO is the only sensible way to disable the data. There are two things to > disable: > nit: I wouldn't choose the word "sensible" given that -OO is already fundamentally unusable without knowing if any code in your entire transitive dependencies might depend on the presence of docstrings... > > * The data in pyc files > * Printing the exception highlighting > > Printing the exception highlighting can be disabled via combo of > environment variable / -X option but collecting the data can only be > disabled by -OO. The reason is that this will end in pyc files > so when the data is not there, a different kind of pyc files need to be > produced and I really don't want to have another set of pyc file extension > just to deactivate this. Notice that also a configure > time variable won't work because it will cause crashes when reading pyc > files produced by the interpreter compiled without the flag. > I don't think the optional existence of column number information needs a different kind of pyc file. Just a flag in a pyc file's header at most. It isn't a new type of file. > On Sat, 8 May 2021 at 21:13, Gregory P. Smith <g...@krypto.org> wrote: > >> >> >> On Sat, May 8, 2021 at 11:58 AM Pablo Galindo Salgado < >> pablog...@gmail.com> wrote: >> >>> Hi Brett, >>> >>> Just to be clear, .pyo files have not existed for a while: >>>> https://www.python.org/dev/peps/pep-0488/. >>> >>> >>> Whoops, my bad, I wanted to refer to the pyc files that are generated >>> with -OO, which have the "opt-2" prefix. >>> >>> This only kicks in at the -OO level. >>> >>> >>> I will correct the PEP so it reflex this more exactly. >>> >>> I personally prefer the idea of dropping the data with -OO since if >>>> you're stripping out docstrings you're already hurting introspection >>>> capabilities in the name of memory. Or one could go as far as to introduce >>>> -Os to do -OO plus dropping this extra data. >>> >>> >>> This is indeed the plan, sorry for the confusion. The opt-out mechanism >>> is using -OO, precisely as we are already dropping other data. >>> >> >> We can't piggy back on -OO as the only way to disable this, it needs to >> have an option of its own. -OO is unusable as code that relies on >> "doc"strings as application data such as >> http://www.dabeaz.com/ply/ply.html exists. >> >> -gps >> >> >>> >>> Thanks for the clarifications! >>> >>> >>> >>> On Sat, 8 May 2021 at 19:41, Brett Cannon <br...@python.org> wrote: >>> >>>> >>>> >>>> On Fri, May 7, 2021 at 7:31 PM Pablo Galindo Salgado < >>>> pablog...@gmail.com> wrote: >>>> >>>>> Although we were originally not sympathetic with it, we may need to >>>>> offer an opt-out mechanism for those users that care about the impact of >>>>> the overhead of the new data in pyc files >>>>> and in in-memory code objectsas was suggested by some folks (Thomas, >>>>> Yury, and others). For this, we could propose that the functionality will >>>>> be deactivated along with the extra >>>>> information when Python is executed in optimized mode (``python -O``) >>>>> and therefore pyo files will not have the overhead associated with the >>>>> extra required data. >>>>> >>>> >>>> Just to be clear, .pyo files have not existed for a while: >>>> https://www.python.org/dev/peps/pep-0488/. >>>> >>>> >>>>> Notice that Python >>>>> already strips docstrings in this mode so it would be "aligned" with >>>>> the current mechanism of optimized mode. >>>>> >>>> >>>> This only kicks in at the -OO level. >>>> >>>> >>>>> >>>>> Although this complicates the implementation, it certainly is still >>>>> much easier than dealing with compression (and more useful for those that >>>>> don't want the feature). Notice that we also >>>>> expect pessimistic results from compression as offsets would be quite >>>>> random (although predominantly in the range 10 - 120). >>>>> >>>> >>>> I personally prefer the idea of dropping the data with -OO since if >>>> you're stripping out docstrings you're already hurting introspection >>>> capabilities in the name of memory. Or one could go as far as to introduce >>>> -Os to do -OO plus dropping this extra data. >>>> >>>> As for .pyc file size, I personally wouldn't worry about it. If someone >>>> is that space-constrained they either aren't using .pyc files or are only >>>> shipping a single set of .pyc files under -OO and skipping source code. And >>>> .pyc files are an implementation detail of CPython so there shouldn't be >>>> too much of a concern for other interpreters. >>>> >>>> -Brett >>>> >>>> >>>>> >>>>> On Sat, 8 May 2021 at 01:56, Pablo Galindo Salgado < >>>>> pablog...@gmail.com> wrote: >>>>> >>>>>> One last note for clarity: that's the increase of size in the stdlib, >>>>>> the increase of size >>>>>> for pyc files goes from 28.471296MB to 34.750464MB, which is an >>>>>> increase of 22%. >>>>>> >>>>>> On Sat, 8 May 2021 at 01:43, Pablo Galindo Salgado < >>>>>> pablog...@gmail.com> wrote: >>>>>> >>>>>>> Some update on the numbers. We have made some draft implementation >>>>>>> to corroborate the >>>>>>> numbers with some more realistic tests and seems that our original >>>>>>> calculations were wrong. >>>>>>> The actual increase in size is quite bigger than previously >>>>>>> advertised: >>>>>>> >>>>>>> Using bytes object to encode the final object and marshalling that >>>>>>> to disk (so using uint8_t) as the underlying >>>>>>> type: >>>>>>> >>>>>>> BEFORE: >>>>>>> >>>>>>> ❯ ./python -m compileall -r 1000 Lib > /dev/null >>>>>>> ❯ du -h Lib -c --max-depth=0 >>>>>>> 70M Lib >>>>>>> 70M total >>>>>>> >>>>>>> AFTER: >>>>>>> ❯ ./python -m compileall -r 1000 Lib > /dev/null >>>>>>> ❯ du -h Lib -c --max-depth=0 >>>>>>> 76M Lib >>>>>>> 76M total >>>>>>> >>>>>>> So that's an increase of 8.56 % over the original value. This is >>>>>>> storing the start offset and end offset with no compression >>>>>>> whatsoever. >>>>>>> >>>>>>> On Fri, 7 May 2021 at 22:45, Pablo Galindo Salgado < >>>>>>> pablog...@gmail.com> wrote: >>>>>>> >>>>>>>> Hi there, >>>>>>>> >>>>>>>> We are preparing a PEP and we would like to start some early >>>>>>>> discussion about one of the main aspects of the PEP. >>>>>>>> >>>>>>>> The work we are preparing is to allow the interpreter to produce >>>>>>>> more fine-grained error messages, pointing to >>>>>>>> the source associated to the instructions that are failing. For >>>>>>>> example: >>>>>>>> >>>>>>>> Traceback (most recent call last): >>>>>>>> >>>>>>>> File "test.py", line 14, in <module> >>>>>>>> >>>>>>>> lel3(x) >>>>>>>> >>>>>>>> ^^^^^^^ >>>>>>>> >>>>>>>> File "test.py", line 12, in lel3 >>>>>>>> >>>>>>>> return lel2(x) / 23 >>>>>>>> >>>>>>>> ^^^^^^^ >>>>>>>> >>>>>>>> File "test.py", line 9, in lel2 >>>>>>>> >>>>>>>> return 25 + lel(x) + lel(x) >>>>>>>> >>>>>>>> ^^^^^^ >>>>>>>> >>>>>>>> File "test.py", line 6, in lel >>>>>>>> >>>>>>>> return 1 + foo(a,b,c=x['z']['x']['y']['z']['y'], d=e) >>>>>>>> >>>>>>>> ^^^^^^^^^^^^^^^^^^^^^ >>>>>>>> >>>>>>>> TypeError: 'NoneType' object is not subscriptable >>>>>>>> >>>>>>>> The cost of this is having the start column number and end >>>>>>>> column number information for every bytecode instruction >>>>>>>> and this is what we want to discuss (there is also some stack cost >>>>>>>> to re-raise exceptions but that's not a big problem in >>>>>>>> any case). Given that column numbers are not very big compared with >>>>>>>> line numbers, we plan to store these as unsigned chars >>>>>>>> or unsigned shorts. We ran some experiments over the standard >>>>>>>> library and we found that the overhead of all pyc files is: >>>>>>>> >>>>>>>> * If we use shorts, the total overhead is ~3% (total size 28MB and >>>>>>>> the extra size is 0.88 MB). >>>>>>>> * If we use chars. the total overhead is ~1.5% (total size 28 MB >>>>>>>> and the extra size is 0.44MB). >>>>>>>> >>>>>>>> One of the disadvantages of using chars is that we can only report >>>>>>>> columns from 1 to 255 so if an error happens in a column >>>>>>>> bigger than that then we would have to exclude it (and not show the >>>>>>>> highlighting) for that frame. Unsigned short will allow >>>>>>>> the values to go from 0 to 65535. >>>>>>>> >>>>>>>> Unfortunately these numbers are not easily compressible, as every >>>>>>>> instruction would have very different offsets. >>>>>>>> >>>>>>>> There is also the possibility of not doing this based on some build >>>>>>>> flag on when using -O to allow users to opt out, but given the fact >>>>>>>> that these numbers can be quite useful to other tools like coverage >>>>>>>> measuring tools, tracers, profilers and the such adding conditional >>>>>>>> logic to many places would complicate the implementation >>>>>>>> considerably and will potentially reduce the usability of those tools >>>>>>>> so we >>>>>>>> prefer >>>>>>>> not to have the conditional logic. We believe this is extra cost is >>>>>>>> very much worth the better error reporting but we understand and >>>>>>>> respect >>>>>>>> other points of view. >>>>>>>> >>>>>>>> Does anyone see a better way to encode this information **without >>>>>>>> complicating a lot the implementation**? What are people thoughts on >>>>>>>> the >>>>>>>> feature? >>>>>>>> >>>>>>>> Thanks in advance, >>>>>>>> >>>>>>>> Regards from cloudy London, >>>>>>>> Pablo Galindo Salgado >>>>>>>> >>>>>>>> _______________________________________________ >>>>> Python-Dev mailing list -- python-dev@python.org >>>>> To unsubscribe send an email to python-dev-le...@python.org >>>>> https://mail.python.org/mailman3/lists/python-dev.python.org/ >>>>> Message archived at >>>>> https://mail.python.org/archives/list/python-dev@python.org/message/JUXUC7TYPAMB4EKW6HJL77ORDYQRJEFG/ >>>>> Code of Conduct: http://python.org/psf/codeofconduct/ >>>>> >>>> _______________________________________________ >>> Python-Dev mailing list -- python-dev@python.org >>> To unsubscribe send an email to python-dev-le...@python.org >>> https://mail.python.org/mailman3/lists/python-dev.python.org/ >>> Message archived at >>> https://mail.python.org/archives/list/python-dev@python.org/message/PDWYJ55Z4XH6OHUQ7IDEG23GWIP6GJOT/ >>> Code of Conduct: http://python.org/psf/codeofconduct/ >>> >>
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