Inada Naoki <songofaca...@gmail.com> added the comment:
> I don't understand how _PyUnicodeWriter could be slow. It does not
> overallocate by default. It's just wrapper to implement efficient memory
> management.
I misunderstood _PyUnicodeWriter. I thought it caused one more allocation, but
it doesn't.
But _PyUnicodeWriter is still slow, because gcc and clang are not smart enough
to optimize _PyUnicodeWriter_Init() & _PyUnicodeWriter_Prepare().
See this example:
```
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#define S(s) (s),strlen(s)
int
main(int argc, char *argv[])
{
Py_Initialize();
for (int i=0; i<100000000; i++) {
//PyObject *s = PyUnicode_FromString("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
PyObject *s = _PyUnicode_FromASCII(S("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"));
Py_DECREF(s);
}
return 0;
}
```
PyUnicode_FromString() takes about 4 sec on my machine. _PyUnicode_FromASCII()
is about 2 sec.
By skipping _PyUnicodeWriter for ASCII string (GH-14283),
PyUnicode_FromString() takes about 3 sec.
```
$ time ./x # PyUnicode_FromString
real 0m4.085s
user 0m4.081s
sys 0m0.004s
$ time ./y # PyUnicode_FromString (skip _PyUnicode_Writer, GH-14283)
real 0m2.988s
user 0m2.988s
sys 0m0.000s
$ time ./z # _PyUnicode_FromASCII
$ time ./z
real 0m1.975s
user 0m1.975s
sys 0m0.000s
```
----------
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue37348>
_______________________________________
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
