Hi, What would be the correct way of locking the bit generator of np.random.Generator in cython's nogil context? (This is threading 101, surely, so please forgive my ignorance).
The docs for extending np.random.Generator in cython (https://numpy.org/doc/stable/reference/random/extending.html#cython) recommend the following idiom for generating uniform variates, where the GIL is released and a Generator-specific lock is held: x = PCG64() rng = <bitgen_t *> PyCapsule_GetPointer(x.capsule, capsule_name) with nogil, x.lock: rng.next_double(rng.state) What is the correct way of locking it when already in the nogil section (so that x.lock is not accessible)? The use case is a long-running MC process which generates random variates in a tight loop (so the loop is all nogil). In case it matters, I probably won't be using python threads, but may use multiprocessing. Basically, cdef double uniform(self) nogil: if self.idx >= self.buf.shape[0]: self._fill() cdef double value = self.buf[self.idx] self.idx += 1 return value cdef void _fill(self) nogil: self.idx = 0 # HERE: Lock ? for i in range(self.buf.shape[0]): self.buf[i] = self.rng.next_double(self.rng.state) Thanks, Evgeni P.S. The full cdef class, for completeness: cdef class RndmWrapper(): cdef: double[::1] buf Py_ssize_t idx bitgen_t *rng object py_gen # keep the garbage collector away def __init__(self, seed=(1234, 0), buf_size=4096, bitgen_kind=None): if bitgen_kind is None: bitgen_kind = PCG64 # cf Numpy-discussion list, K.~Sheppard, R.~Kern, June 29, 2020 and below # https://mail.python.org/pipermail/numpy-discussion/2020-June/080794.html entropy, num = seed seed_seq = SeedSequence(entropy, spawn_key=(num,)) py_gen = bitgen_kind(seed_seq) # store the python object to avoid it being garbage collected self.py_gen = py_gen capsule = py_gen.capsule self.rng = <bitgen_t *>PyCapsule_GetPointer(capsule, capsule_name) if not PyCapsule_IsValid(capsule, capsule_name): raise ValueError("Invalid pointer to anon_func_state") self.buf = np.empty(buf_size, dtype='float64') self._fill() @cython.boundscheck(False) @cython.wraparound(False) cdef void _fill(self) nogil: self.idx = 0 for i in range(self.buf.shape[0]): self.buf[i] = self.rng.next_double(self.rng.state) @cython.boundscheck(False) @cython.wraparound(False) cdef double uniform(self) nogil: if self.idx >= self.buf.shape[0]: self._fill() cdef double value = self.buf[self.idx] self.idx += 1 return value _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
