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Pythons -O flag makes an insane difference

See original GitHub issue

This is just something I noted

Running a script that spends most of its time in pywasm’s exec:

$ time python main.py
real	2m0,034s
user	2m0,305s
sys	0m0,644s

And with optimizations enabled:

$ time python -O main.py
real	0m0,449s
user	0m0,908s
sys	0m0,481s

According to this -O eliminates assert statements. Not sure how much this impacts security.

Edit: ok, it seems that the code is not executed correctly, I’ll have a look

I get this:

  File "main.py", line 193, in play
    runtime = pywasm.load(runtime, {
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/__init__.py", line 98, in load
    module = binary.Module.from_reader(f)
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 1084, in from_reader
    type_section = TypeSection.from_reader(section_reader)
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 445, in from_reader
    o.data = [FunctionType.from_reader(r) for _ in range(n)]
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 445, in <listcomp>
    o.data = [FunctionType.from_reader(r) for _ in range(n)]
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 70, in from_reader
    o.args = ResultType.from_reader(r)
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 51, in from_reader
    o.data = [ValueType.from_reader(r) for i in range(n)]
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 51, in <listcomp>
    o.data = [ValueType.from_reader(r) for i in range(n)]
  File "/home/one/.pyenv/versions/3.8.2/lib/python3.8/site-packages/pywasm/binary.py", line 33, in from_reader
    return ValueType(ord(r.read(1)))
Exception ord() expected a character, but string of length 0 found

Ah, looking through the pywasm code it seems that the asserts have side effects, that are necessary for it to be executed correctly.

Issue Analytics

State:
Created 3 years ago
Comments:6 (4 by maintainers)

Top GitHub Comments

1reaction

mohansoncommented, Jan 3, 2021

I fixed the side effects of assertion in pywasm==1.0.7, and at the same time improved the performance (about ~10%). I think I have a chance to double the running speed, but I need to think more (that is, not in this version).

-O won’t break the program anymore.

1reaction

mohansoncommented, Jan 2, 2021

I recently started learning chess (because of The Queen’s Gambit

Maybe I will participate 😃