CPython JIT
= CPython JIT
{c}
Added in <CPython 3.13>.
To enable tested on <Ubuntu 25.04>:
``
git clone https://github.com/python/cpython
cd cpython
git checkout v3.13.7
./configure --enable-experimental-jit
make -j
``
However, the JIT appears to be useless tested as of this Python version, lol:
* https://news.ycombinator.com/item?id=44476023
* https://devclass.com/2025/07/09/despite-30-months-work-core-developer-says-pythons-jit-compiler-is-often-slower-than-the-interpreter/
* https://fidget-spinner.github.io/posts/jit-reflections.html
We can try to test it with \a[python/inc_loop.py]:
``
time ./python python/inc_loop.py 10000000
``
but the result is just as pathetic as without JIT currently, taking about 1 second for only 10m loops.
This can be compared with the optimal assembly from \a[c/inc_loop_asm.c]:
``
time ./inc_loop_asm.out 1000000000
``
which does 1 billion loops in about half a second on <Ciro Santilli's hardware/P14s>.
For comparison, <PyPy> actually speeds things up and does 1 billion loops in about a second, so only 2x worse than native.
TODO triple check that JIT is enabled. Many threads say the command is:
``
./python -c 'import sysconfig; sysconfig.get_config_var("JIT_DEPS")'
``
but that fails with:
``
ModuleNotFoundError: No module named '_sysconfigdata__linux_x86_64-linux-gnu'
``
For comparison with a properly implemented dynamic language JIT running \a[nodejs/inc_loop.js] does 1 billion loops in 0.6s on v22.14.0, close to native.
https://tonybaloney.github.io/posts/python-gets-a-jit.html documents what the initial "JIT" implementation does. It is just an extremely naive concatenation of instructions that avoids a for + switch. No wonder it doesn't speed things up much at all.