[Python-Dev] Re: _PyBytesWriter/_PyUnicodeWriter could be faster

2020年10月28日 00:26:25 -0700

Thanks for your very informative reply.
I replied you in issue41486. Maybe memory blocks will not bring performance 
improvement to _PyBytesWriter/_PyUnicodeWriter, which is a bit frustrating.
> For a+b, Python first computes "a", then "b", and finally "a+b". I don't see 
> how your API could optimize such code.
I mean this situation:
 s = 'a' * 100_000_000 + '\uABCD'
 b = s.encode('utf-8')
 b.encode('utf-8') # <- this situation
I realize I was wrong, the UCS1->UCS2 transformation will only be done once, it 
only saves a memcpy().
Even in this case it will only save two memcpy():
 s = 'a' * 100_000_000 + '\uABCD' * 100_000_000 + '\U00012345'
 b = s.encode('utf-8')
 b.encode('utf-8')
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