repeated from c.l.p : "Feature Request: Py_NewInterpreter to create separate GIL (branch)"
Daniel Dittmar wrote:
I'd like to use multiple CPU cores for selected time consuming Python computations (incl. numpy/scipy) in a frictionless manner.
Interprocess communication is tedious and out of question, so I thought about simply using a more Python interpreter instances (Py_NewInterpreter) with extra GIL in the same process.
If I understand Python/ceval.c, the GIL is really global, not specific to an interpreter instance: static PyThread_type_lock interpreter_lock = 0; /* This is the GIL */
Thats the show stopper as of now. There are only a handfull funcs in ceval.c to use that very global lock. The rest uses that funcs around thread states.
Would it be a possibilty in next Python to have the lock separate for each Interpreter instance. Thus: have *interpreter_lock separate in each PyThreadState instance and only threads of same Interpreter have same GIL? Separation between Interpreters seems to be enough. The Interpreter runs mainly on the stack. Possibly only very few global C-level resources would require individual extra locks.
Sooner or later Python will have to answer the multi-processor question. A per-interpreter GIL and a nice module for tunneling Python-Objects directly between Interpreters inside one process might be the answer at the right border-line ? Existing extension code base would remain compatible, as far as there is already decent locking on module globals, which is the the usual case.